2000 C5 convertible electrical fault?

PhilHarris

CCCUK Member
Hi, I may have an issue with my C5. One day last week I went to start the car, but found the battery was flat. I took the battery out to charge it but it was totally dead. I bought a new battery, but when I connected it (with the keys out of the ignition) I noticed a slight spark, checking with an ammeter it was drawing 4 to 5 amps. The first thing I tried was disconnecting the alternator output (in case the rectifier was faulty), however the problem persisted. I then noticed the interior lights were on so I pulled the plug into the door mirror, yet the problem persisted. When I touch the terminal on the battery I hear a slight clunking which seems to come from the RH side headlamp actuator, I since tried disconnecting the multi-plug to both headlights yet to no avail. At the moment I've left the battery disconnected as I don't want to kill another battery. Does anyone have any ideas please? Phil
 

Oneball

CCCUK Member
Most modern cars will be running electrical systems up to 30mins after locking or unlocking. The only way to find out for sure if you’ve actually got something draining the battery is to do a parasitic battery drain test. Have a google for instructions. Remember most multimeters work in the mA range so no turning headlight on or trying to start.
 

PhilHarris

CCCUK Member
Many thanks, I will look up parasitic battery drain testing. One thing I didn't mention is that I removed and replaced each fuse whilst checking if the battery drain was still present and it was, whatever it is it is not supplied from the main fuse box (are there other fuses elsewhere?). Thanks for the comment on multimeters, but I'm from an electronic background. Phil
 

teamzr1

Supporting vendor
As mentioned any time there is a loss of battery and then returned all the C5 controllers will wake from sleep mode and be on for like 10 minutes and draw voltage/current and then go back to sleep and that drain would go away so be sure you wait long enough to be sure there is a drain issue
On the outside corned of the fuse panel in the engine bay there is a small plastic cover and when opened you see a mid-sized wire connected
Removing that wire kills off voltage to the fuse panel under the kick panel of passenger floor
With that wire disconnected would then if still having a draw, it would have to be something within the engine bay fuse panel

Along with fuses, there are square relays they plug in and could be taken off to see if the relay is stuck closed

Components most likely to cause a parasitic draw on the 12V battery on GM models include switches, relays, LIN buses and control modules. A new voltage drop test in Service Information (SI) can help in determining which component may be causing a parasitic draw.

If there is an excessive load on the electrical system that is draining the battery after the ignition is turned off, review the Battery Electrical Drain/Parasitic Load Test document under 12V Charging and Starting > Diagnostic Information and Procedures in the Service Information.
It features updated information on diagnostic aids, system verification and testing, including a new parasitic draw voltage drop test and a battery draw verification sheet to help with diagnosis.

Several tables have been added in SI that list the milliAmps (mA) value across the fuses in a fuse block. Use a DMM set to mV scale to check the voltage drop between the battery positive post and each leg of the battery junction block (if equipped) to determine which fuse block contains the draw.

Once the fuse block feed with the highest draw has been identified, go to that fuse block and check voltage drop across fuses, excluding J-case type fuses, one at a time. For three-bladed fuses, the center of the fuse is the supply voltage for both sides of the fuse.
Compare the reading to the corresponding fuse in the table. If voltage drop is found, refer to the Power Distribution Schematics to diagnose exactly which circuit of a suspected system is causing the high parasitic drain.

Testing Set Up

To begin diagnosis of a parasitic draw, it’s important to properly set up the test.
There are many things that can prevent the vehicle from completely going to sleep and passing the parasitic draw test.

1. Road test the vehicle and operate all accessories to check for proper operation.
2. Connect a 50 Amp inductive amp clamp to the negative battery cable that can read down to 1 mA.
3. With the ignition Off, open all doors, hood, trunk/liftgate (to gain access to all components and fuse blocks) and manually close all latches and switches.
4. Lock the vehicle with the key fob and move the fob a safe distance so it doesn’t wake up the vehicle (distance depends on approach detection of the vehicle).
5. With all modules and components asleep, monitor the amperage. After approximately 10 minutes, amperage should drop to a stable value less than 20 mA.
• If amperage is 40mA or higher, follow the fuse voltage drop test to identify the fuse(s) with an ongoing draw.
• Measure all fuses and record voltage drop, fuse location, type and rating.
6. After all fuses are tested, identify the suspect circuits and calculate the amperage for each.

If there are multiple control modules drawing amperage, work from the least complex component to the most. For example, for a drain on the Memory Seat Module, Body Control Module and Gateway Module, remove power to the Memory Seat Module first and verify if the other modules go to sleep properly.
In many cases, a “satellite” module like the Memory Seat Module is the most likely to cause a system to wake up.

Battery Draw Customer Verification Worksheet

The new Customer Concern Verification Sheet (CCVS) Battery Draw worksheet may be helpful in isolating or duplicating a customer’s concern. Use the information during the road test to verify operation according to the customer’s description of the condition.
A link to the worksheet is included in the Battery Electrical Drain/Parasitic Load Test document in SI. The worksheet also can be found in GM GlobalConnect. From the Service apps, launch Service Forms and select CCVS Battery Draw

All Customer Concern Verification Sheets (CCVS) have been designed to improve communications between service customers and technicians.
The more clearly concerns and related symptoms are understood, the more likely the concern will be fixed quickly and accurately.

System Operation

When diagnosing a parasitic draw, keep in mind the power-down and wake-up process for most control modules.

After the ignition is turned off, the control modules will begin to go to sleep (shut off).
However, not all control modules go to sleep at the same time. Some control modules may take up to 30 minutes or longer after turning the ignition off before going to sleep (e.g. Retained Accessory Power).
Other components, such as EVAP, HVAC Afterblow, EV Battery Heater/Coolers, OnStar and Remote Keyless Entry (approach detection in keyless access vehicles), may periodically wake up control modules and then go back to sleep, depending on vehicle status. These are all normal conditions.

Most vehicle systems will go into the initial sleep cycle after 10 minutes.
With periodic normal wake up cycles that will occur for approximately one second, it can take up to two hours before all systems power down completely.
Typically, a vehicle will not have more than a 50 mA parasitic draw during the initial power sleep cycle.

There are many things that can prevent the vehicle from completely going to sleep and passing the parasitic draw test, such as the key fob not moved away from the vehicle (for keyless access vehicles); the approach, exit, or delayed lighting not disabled; or HVAC Afterblow, which is enabled at the factory on some 2021 models, cannot be disabled.
Some vehicles can have the power supply port changed to “ON” with the key off to allow for accessories to stay powered (e.g., phone charger).
Ensure all aftermarket accessories are unplugged prior to testing.
The use of a Digital Multimeter (DMM) set to Min/Max may help identify the normal spikes in the parasitic draws.
 

teamzr1

Supporting vendor
Many control modules in a vehicle stay awake for different amounts of time after the ignition is turned off.
To help with diagnosis of parasitic drains, a Vehicle Time Out chart has been developed for 2015 ATS, ATS-V; 2017 LaCrosse, CT6, CTS, XT5, Corvette, Acadia (VIN N); and 2016 Camaro models listing the times after a specific event that certain modules stay awake.
Components most likely to cause a parasitic draw on a vehicle’s battery are switches, relays, and control modules.

The charts list the amount of time the modules controlling the HVAC, Flashers, Infotainment/DIC, Drive Mode Switch, Park Assist, Headlamps, and Engine Start/Stop features are awake after each of three specific events — door open/close, key fob unlock, and passive unlock.

Refer to Bulletin #16-NA-272 for the chart.
It is not a complete listing of all modules that may be active after the ignition is turned off (for example, the interior lights), but includes the most common.
Of the modules or switches that are listed, the backlighting or status LED will be on for the time listed.

Powering Down

After the ignition is turned off, the control modules will begin to go to sleep.
However, all control modules do not go to sleep at the same time; some may take up to 30 minutes or longer after turning the ignition off before going to sleep. Other modules may periodically wake up and then go back to sleep.
It can take up to two hours before all systems power down, allowing the parasitic draw test to pass.
An occasional increase in the parasitic draw is normal as long as it returns within one second.
These are all normal conditions.

There are many things that can prevent a vehicle from completely going to sleep and passing the parasitic draw test.
Make sure all the following conditions are met before performing the parasitic current draw test using the EL 38758 parasitic draw test switch.

• Ignition off
• Key out of the ignition switch – when not equipped with keyless access and start
• Retained Accessory Power off – open and close the driver’s door after turning off the ignition
• Scan tool not communicating with a vehicle control module – in some cases it may need to be disconnected from the DLC
• All access doors closed
• Headlamps off – Auto headlamps disabled
• Any delay lighting off
• Disable any underhood lamp, if equipped
• HVAC afterblow off
• Any accessory that can work with ignition off is inactive or off
• Wait up to two minutes or longer, after all other listed conditions are met

Some parasitic drains can be difficult to diagnose, especially if other components are causing a module to remain awake.
For example, Bulletin #16-NA-126 covers an intermittent dead battery condition on 2016 Cascada models.
In this case, if the battery drops below 65% state of charge, the tail lamps send a diagnostic request to the BCM, which causes everything on the BUS to wake up and remain awake until the battery drains.
A new tail lamp part number has been released to address this condition.

For additional information on parasitic drains and related conditions, always review the latest bulletins as well as the parasitic drain diagnostics in the appropriate Service Information.
 

teamzr1

Supporting vendor
Condition/Concern:
Platform Battery Drain Diagnosis Process - Battery is discharged for no apparent reason while vehicle is parked and locked - Intermittent draw and/or possible continuous draw(s) that slowly renders the battery below its serviceable voltage amperage level.

Please follow this process entirely:

Define the conditions which trigger the discharged battery:
• How long does it take for the battery to discharge? This step will help determine if the draw is large or small.
Normally a draw, which takes the battery level down overnight after operating the vehicle the day before, is rather large and is related to a switch, relay or other electric/mechanical device.
Small amounts of drain which take several days to take the battery from a good state of charge to below the level required to start the engine can be small single bulbs or modules which are either not going to sleep when they should, or waking up intermittently for some unknown reason.

• How many times has it happened to the customer? This step will determine if this is a Random occurrence and/or intermittent.

• Does it always happen in the same location? Is there some outside influence that surrounds the vehicle that needs to be taken into account? This is most unlikely, but worth checking-out.

• Describe the customer's driving habits. Does the battery get to a state of being fully charged on a regular basis or is this vehicle unable to crank due to a generally low state of charge?

• Is the vehicle equipped with any non-original equipment including cell phone, remote starter, extra lighting, radio, CD player, LOJAK, etc. or OnStar (either dealer or factory installed)?
All of these items can be wired in such a way to either constantly draw amperage, which they shouldn't, or in some way affect the class 2 modules on this vehicle and/or the battery and charging system.

• Does the customer leave the key in the ignition? Leaving the key in the ignition does not generally cause a problem, but if the customer does not come back to the locked ignition position after shutting the engine off however, many draws will be induced.
This draw will not be reduced and/or eliminated, this type of draw is due to the fact that the system is designed to keep certain modules awake with the key in this position.

• What is the previous history on this car, what parts have been replaced, what repairs have been performed either in an attempt to correct this situation or that might impact it?

Are there any other reported problems with the vehicle which may relate to a discharged battery concern - items which were previously reported/corrected and/or currently exist that the customer (car recently bought used) does not recognize as a problem or the used car manager reporting the discharged battery is unaware of? Recent repairs may or may not relate to draw diagnosis; i.e. the IPC was replaced recently.

Perform a good visual and physical inspection of the battery cables. CHECK TORQUE OF BATTERY CABLE BOLTS. If loose, check for signs of arcing and corrosion etc., grounds and power leads to and from each of these, or BOLT MATERIAL IN BATTERY THREADS, THERMISTOR (if equipped) CONNECTOR FOR PROPER SEATING AND TIGHTNESS.
What are the results of a battery/CHARGING SYSTEM test?

• Perform a generator output test and a terminal drag test on generator terminal L.

• Fuses related to this concern: check for loose fuses in trunk and engine compartment bussed electrical center by rocking each fuse with one finger, which may help identify the fuse.

The only repairs that may be made to the electrical center are replacement of plug-in devices and mounting hardware, as follows: fuses, relays, circuit breakers, electrical center cover, battery stud cover, and other snap-on covers, cover attachment thumb screw, labels for fuse/relay identification, splash shields, and mounting brackets

What DTCs are currently present or have been recorded on previous visits to the dealer? Correct as per the appropriate service manual.
Road test vehicle for 30-40 minutes, activate all accessories. Open and close all doors, windows, deck lid, etc. CYCLE LUMBAR AND SEAT SWITCHES along with all other manually operated switches including the trunk release, fuel door release, garage door opener, and valet that have power to them all the time while the car is sitting. Don't forget to look FOR A STUCK SWITCH/RELAY.

What is the parasitic draw on the vehicle after a 25-minute power down cycle? Using parasitic draw test switch tool J38758 and DVOM J39200, perform a parasitic draw test as per the procedure in the Engine Electrical section Service Information. Record the draw and read the reserve capacity of the battery in the vehicle.

Divide the reserve capacity by four (4) and the draw present should not exceed this number. Example: If the battery has a reserve capacity of 100 amperes, the current draw should not exceed 25 mA on the DVOM. See SI for acceptable draw limits for each module the vehicle may be equipped with. Keep in mind the draw created by the OnStar system for the first 48 hours from ignition off.

The system will cycle every 10 minutes and cause a spike to approximately 250 mA for about ten seconds, taper down to 75 mA for another 45 seconds and go to less than one mA for the nine minutes until the next cycle begins. This is normal. The Class 2 data line should not wake up during this sequence.

This cycle stops if power is removed from the OnStar system for a short period and will resume once the GPS signal is reacquired.
If the draw above is determined to be above the appropriate amount for the vehicle involved, are any modules on the class 2 data line staying "active" past the 25-minute time out mentioned above or waking up periodically after this time-out has passed?

If one or more module is waking up, how many times and which module(s)? Use the Tech 2 and use the message monitor screen with an external power source to the Tech 2 if performing an amp draw test while using message monitor.

Here is a suggested procedure for performing a combination parasitic draw test while monitoring the class 2 devices on the vehicle:

Remove terminal 16 from data link connector (DLC).
Install tool #J38758 on battery.
Connect Fluke 87 to J38758 as described in the Engine Electrical section of the appropriate Service Manual and set to appropriate amp scale.
Connect Tech 2 to DLC
Connect 110-volt power supply to DLC end of Tech 2 cable.
Turn Tech 2 on
• Main, enter
• Diagnostics enter.
• Year
• Vehicle type
• Diagnostic circuit check
• Class 2 message monitor - remember; only modules which are currently communicating on the Class 2 data line will show up on the message monitor screen.

If the ignition is in the accessory position as an example, the PCM and ABS controller will not be listed. If a module, which the vehicle is known to be equipped with, does not show up on message monitor when in the run position, this indicates a problem that needs correction prior to proceeding.

Allow the vehicle to sit with all doors closed and without activating any switches etc. until the class 2 system has had enough time to power down, less than 25 minutes, or use the sleep mode to put all the modules to sleep.

Once the sleep mode is enabled, the first module to "wake up" will be listed first on the message monitor screen with others listed in order of "wake up". The time from being put to sleep until the first "wake up" sequence will also be displayed.

If a combination of three or four modules has come active, putting all of the modules back to sleep and pulling the fuse to one module at a time will help to narrow down which module may be waking up inadvertently.

Remember that module "wake up" can be caused by several factors.

They include, but are not limited to:
• input changing states - door switch going open and closed (hi/lo)
• power or ground coming and going to module
• module internal function incorrect
• Or in the case of the power master, amperage draws in excess of low power requirements or another module which has these or other related concerns.
These all can be checked with the Fluke set to 1 millisecond record speed on min/max setting.

Open the gate on J38758, and let vehicle sit for another ten (10) minutes and/or use sleep mode.
Review the amperage reading.
As the amperage draw tapers down below 10 amps, close the J38758 and switch Fluke 87 to milliamp scale and record min/max on 100-millisecond scale.

Open the J38758 again when done. This step will allow the Fluke meter to record any spikes and keep the meter working during the entire sequence. IF MIN/MAX IS NOT SELECTED, THE METER WILL TIME OUT AND SHUT OFF.
After the vehicle has been sitting for the necessary time, check the number of counts as per message monitor for each control module, i.e. each time a unit goes from inactive, to active and inactive again.
The module(s) with the highest number of counts may indicate a suspect area. Modules may be waking up on their own, (which is most unlikely) or activated by a switch input, power fluctuation, poor ground or input from other modules which are being activated.

Once it has been determined that the draw is either a component - relay, switch etc., which is stuck or in some way reduces/contributes to the draw, determine which circuits are specifically involved.

Touching and/or removing fuses, relays, and connectors to suspect components after reviewing the current wiring diagram until the draw is reduced to acceptable levels will lead to the correct circuit.

When exiting the message monitor screen and then re-entering the message monitor screen, the Tech 2 will also wake up modules. DON'T BE FOOLED. Wait for the module(s) to again go to sleep or use the sleep mode function.
 

PhilHarris

CCCUK Member
The reply I've had to my problem is quite frankly stunning, many thanks to teamzr1, Stingray and Oneball for your feedback. I'm going to collate all your comments and keep them as a valued Word document. Clearly I will start with simply doing a current check after 30mins or so, hopefully I'm panicking about nothing.
Phil
 

teamzr1

Supporting vendor
At the least, measure the voltage of the charged battery now, should be around 13 volts
then after connected and waiting for controllers to go to sleep measure the battery again and see if any real voltage drop
Check again after more time would say if any real current draw which should be less than about 40 mAmps a day, battery should be around
mid 12 volts with car off.
 

PhilHarris

CCCUK Member
Hello, I realise this is a long ongoing issue. Once again the background is that I bought a used replacement BCM for my 2000 C5 from VetteSource because my present BCM has a parasitic current drain issue. After going through the code learning process the car turns over a starts for a split second, then stops. I videoed this problem and I sent it to Brian German at VetteSource who said the module is definitely not learning the security code. Is there a preferred Corvette service company in the UK that I could speak to regarding this problem that is perhaps familiar with a Tech2 communicator, there are companies local to me offering Tech2 services but I'd rather use a company familar with C5 systems, maybe to copy over settings into the replacement module. Phil.
 

teamzr1

Supporting vendor
Phil

Have you done either of these 2 relearn processes for the PCM and PCM to sync up the security seed code ?
Must use some way to measure the elapsed time for each steps below
If so, which relearn process did you do ?
I would do the process further down first and if assured doing the elapsed times and security light still does not flash when drivers door is open then try the relearn process just below this :

For newer years, C5 years

Any time a PCM or PCM is replaced it may require a relearn process to be done so that the security seeds are swapped between the 2, and you need to do this process if after the swap and engine will not start

Turn ON the ignition, leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF for 11 minutes, or until DTC P1630 sets.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF, and wait 30 seconds.


Attempt to start the engine. If the engine does not start, Refer to the Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.

Important:
Performing this procedure may cause a DTC P1630 to set. If a DTC P1630 sets, turn OFF the ignition for 30 seconds, then turn ON the ignition. If the DTC P1630 does not clear, Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.

--------------------------------------

Early C5s

Programming Theft Deterrent System Components

Important:

• The body control module (BCM) must be programmed with the proper RPO configurations before performing learn procedures. Refer to Body Control Module (BCM) Programming/RPO Configuration .

• If replacing the BCM with a GM Service Parts Operations (SPO) replacement part, the module will learn the passkey data code immediately. The existing PCM however, must learn the new fuel continue password when the BCM is replaced.

• If replacing a PCM with a GM Service Parts Operations (SPO) replacement part, after programming, these modules will learn the incoming fuel continue password immediately upon receipt of a password message.

Once a password message is received, and a password is learned, a learn procedure must be performed to change this password again. A PCM which has been previously installed in another vehicle will have learned the other vehicle's fuel continue password and will require a learn procedure after programming to learn the current vehicle's password.

Conditions
Use these procedures after replacing:

• BCM
• PCM

10 Minute Learn Procedure
Tools Required
• Tech 2

• Techline terminal with current SPS (Service Programming System) software

Connect the Tech 2 to the vehicle.
Select "Request Information" under "Service Programming".
Disconnect the Tech 2 from the vehicle and connect it to a Techline terminal.
On the Techline terminal, select "Theft Module Re-Learn" under "Service Programming".
Disconnect the Tech 2 from the Techline terminal and connect it to the vehicle.
Turn ON the ignition, with the engine OFF.
Select "VTD Re-Learn" under "Service Programming".
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF (the vehicle is now ready to relearn the password on the next ignition switch transition from OFF to CRANK).
Turn OFF the ignition, and wait 5 seconds.
Start the engine (the vehicle has now learned the password).
With the Tech 2 (scan tool), clear any DTCs.

OR by this Method
30 Minute Learn Procedure

1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON (vehicle will not start).
3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds.

5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the password on the next ignition switch transition from OFF to CRANK).

Important:

The vehicle learns the password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

Start the engine (the vehicle has now learned the password).
With a scan tool, clear any DTCs if needed (history DTCs will self clear after 100 ignition cycles).
 

PhilHarris

CCCUK Member
Phil

Have you done either of these 2 relearn processes for the PCM and PCM to sync up the security seed code ?
Must use some way to measure the elapsed time for each steps below
If so, which relearn process did you do ?
I would do the process further down first and if assured doing the elapsed times and security light still does not flash when drivers door is open then try the relearn process just below this :

For newer years, C5 years

Any time a PCM or PCM is replaced it may require a relearn process to be done so that the security seeds are swapped between the 2, and you need to do this process if after the swap and engine will not start

Turn ON the ignition, leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF for 11 minutes.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF for 11 minutes, or until DTC P1630 sets.
Turn OFF the ignition for 30 seconds.
Turn ON the ignition, leaving the engine OFF, and wait 30 seconds.


Attempt to start the engine. If the engine does not start, Refer to the Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.

Important:
Performing this procedure may cause a DTC P1630 to set. If a DTC P1630 sets, turn OFF the ignition for 30 seconds, then turn ON the ignition. If the DTC P1630 does not clear, Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.

--------------------------------------

Early C5s

Programming Theft Deterrent System Components

Important:

• The body control module (BCM) must be programmed with the proper RPO configurations before performing learn procedures. Refer to Body Control Module (BCM) Programming/RPO Configuration .

• If replacing the BCM with a GM Service Parts Operations (SPO) replacement part, the module will learn the passkey data code immediately. The existing PCM however, must learn the new fuel continue password when the BCM is replaced.

• If replacing a PCM with a GM Service Parts Operations (SPO) replacement part, after programming, these modules will learn the incoming fuel continue password immediately upon receipt of a password message.

Once a password message is received, and a password is learned, a learn procedure must be performed to change this password again. A PCM which has been previously installed in another vehicle will have learned the other vehicle's fuel continue password and will require a learn procedure after programming to learn the current vehicle's password.

Conditions
Use these procedures after replacing:

• BCM
• PCM

10 Minute Learn Procedure
Tools Required
• Tech 2

• Techline terminal with current SPS (Service Programming System) software

Connect the Tech 2 to the vehicle.
Select "Request Information" under "Service Programming".
Disconnect the Tech 2 from the vehicle and connect it to a Techline terminal.
On the Techline terminal, select "Theft Module Re-Learn" under "Service Programming".
Disconnect the Tech 2 from the Techline terminal and connect it to the vehicle.
Turn ON the ignition, with the engine OFF.
Select "VTD Re-Learn" under "Service Programming".
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF (the vehicle is now ready to relearn the password on the next ignition switch transition from OFF to CRANK).
Turn OFF the ignition, and wait 5 seconds.
Start the engine (the vehicle has now learned the password).
With the Tech 2 (scan tool), clear any DTCs.

OR by this Method
30 Minute Learn Procedure

1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON (vehicle will not start).
3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds.

5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the password on the next ignition switch transition from OFF to CRANK).

Important:

The vehicle learns the password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

Start the engine (the vehicle has now learned the password).
With a scan tool, clear any DTCs if needed (history DTCs will self clear after 100 ignition cycles).
Many thanks, I will try that tomorrow and I'm very grateful !
 

teamzr1

Supporting vendor
Many thanks, I will try that tomorrow and I'm very grateful !

Being this PCM/BCM relearn takes over 30 minutes to do,
I highly suggest you either have a battery tender connected or, at the least, make sure the battery is fully charged

And all other electronics are OFF as doing this with ign key ON, engine off, so not even having the doors open
If before turning ign ON, place the parking brake ON as that should tell the BCM when key on to not turn on the parking lights.

When BCM/PCM are not learned security code, then the security light on the dash is hard on when the door is opened

When the relearn test is done correctly, then the light begins to normally flash again when the door is opened
and it would trip a security error code that needs to be erased

Remember you need a stop watch, etc to do the elapsed time when ign key is off and on steps are done

GM made this hard and test time to prevent Aholes from trying to steal a Corvette by swapping a controller
so reason long relearn elapsed time
 

oelarse

Well-known user
When you wan't to identy the fuse with unwanted current draw ithe the C5 fuseboxes (under hood and passenger side footwell) you can open passenger side of car
and active the doorlock shown below first and wait approx 15 min until BCM has gone to sleep.

Then you measure the voltage above all fuses without waking up the BCM in the passenger footwell .
The voltage will in the mV range .When I checked my foglights ON/OFF is caused a 30mV voltagedrop above the fuse (shown below) :)

This video has good info on this issue
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