SWPS Centering.

[teamzr1]

For every action, there is a reaction and in this case the action is the EBCM trips the C1288 DTC
it has done so with 2 different SWPS, so to me, you're spending a lot of time on SWPS and unless both could have the
same failure then you're spending a lot of time looking what the real cause is

I posted yesterday the GM definition of the action of causing C1288 to trip and then the reaction to it
I suggest you reread that and break it down into detail
If in fact the EBCM is seeing an issue to trips that DTC then can prove the reaction which is when C1288 trips
does EBCM trip any of the 4 wheels brakes via the solenoids of ABS

You can prove or disprove that by clearing the code, then recording the PIDS I mentioned and see if any of the 4 wheels ABS solenoids as I show again with the PIDs I show here
Clearly it truly a reason EBCM action in tripping C1288 then the HOLD and Release PIDs would show that and which wheel(s) brakes, even slightly

IF EBCM does command ABS then I would look at the YAW sensor causing the action
IF EBCM does not command ABS when DTC trips than it now to me points to either a EBCM fault, or wiring or ground issues

Monitor the digital SWPS bias correction, Lateral accelerometer and Yaw PIDs to see what that bias data you have is.



As I mentioned and there were another members post I mentioned failures with EBCM as to cracked solder joints or the small relay, common failures
Both can be repaired by yourself or someone else.

1997 and 98 C5s have EBCM in the ass end, due to water splashing back there it caused lots of wiring, grounds and EBCM problems so much so that in 1999 as mine is GM moved the EBCM up front by steering rack

Another main issues are ground points and the electronics highly depend on good ground connections
Throughout the car is ground spice packs. This is where several grounds are spliced inside the ground pack
From the outside the pack might look nice and clean but when you pry the top off then find a fricking mess
as high corrosion so I would look at the ground splice pack that includes the grounds for EBCM, wheel speed sensors , etc

I maybe wrong, but the YAW sensor might be mounted under passenger seat, else behind dash

I will try today to take my 1999 for a testdrive and record all the PIDs I showed about, so you could compare mine with yours.

Splice pack good condition




But can be this bad inside



Looks like this mounted to frame, assure also the frame and mounting bolts is very clean and tight

 

[clive f]

Today I cleared all codes using the tech 2 and went for a drive, the codes showing now are these.


once the TCS warning light came up on the dash I stopped with engine still running and connected the tech 2 and drove showing wheel speed data, all four wheels showing exactly the same speed, so from this I can assume the wheel sensors are not causing any issue, and also the abs, nothing different on any of the solenoids on the data screen. I cannot find anything on the tech 2 about YAW sensor at all, is that because my old tech 2 is not as good as what data is shown on your computer screen, I`d imaging my old tech 2 is very basic in comparison?
voltage readings on swsp now getting erratic seems slow to respond yet yesterday on graph screen it was prefect and smooth, also analogue steering angle was on zero for some time and then decided to play ball when I got home, swps test afterwards still shows analogue to zero giving digital to 30deg.
All splice packs on the car have been removed by a previous owner and replaced with stainless steel block connectors, bolted to the chassis, I`ve been through and checked and cleaned all earthing points, so doe this lead me to think its an ECBM issue and it needs to be taken apart, I`m still not convinced this is possible with the model/year that I have, on the spare one that was on the car when I bought it, you can remove the screws holding the board in place but the board is bonded in place from the underside which you cant get to, happy to be proved wrong though.

 

[teamzr1]

It sure looks like the problem is random and not clearly repeatable as now you're showing more DTCs then before
I really would focus your time and effort on the EBCM and its wiring, including grounds
Possible of borrowing or using a different EBCM to compare ?

Could be bad crimps of wiring connectors or pins

The EBCM is filled with some sticky crap and have to pry the 2 halves apart
Look for the other post we did on this as to repairing solder joints and small relay, one member in last week or 2 just worked on
his EBCM and difficulties are gone

I just got back from doing a testrun for you and will analyze and post data on EBCM PIDs and values and port for you

Tech-II you have I suspect is old and not updated, and it is limited on what PIDS you can see at same time as what I use
I can monitor and record all 90 PIDs concurrently

You UK Corvette/GM owners need to gang up and get a decent full OBD-I and II scanner that works off a laptop and allows
much better access than what you're using

 

[clive f]

thanks Teamzr1, I`m taking a trip up to the nearest corvette garage to me tomorrow, a bit of a pain as I live on an island, so hoping he can confirm your findings, or fix or finds something so obvious that all will be right with the world again, electronics are`nt not my strongpoint at all, plus I think you need to be a bit of a detective, Ive owned over 60 cars in my lifetime and come across nothing as complex as the electrics on a corvette, especially when you can no longer buy spare parts for them............fingers crossed that tomorrow is a good day and not a waste of time and money.

 

[teamzr1]

Went on about 22 mile testrun and recorded all EBCM PIDs

Here is all 4 wheel speed sensors, Speedo and YAW
I superimposed the 2 front and then 2 rears to see if any difference and then compare to speedo

YAW even though on purpose I did hard turns at speed and moved steering wheel hard left to right while driving
YAW never reported over 0.5 degree error

 

[teamzr1]

Here I superimposed all 4 wheels as to see if ABS set a hold or release to any of them even though forcing hard sudden turns of steering wheel
and also rough road PID
This testrun I left active handling and traction control to be controlled by the BCM, rather than having those turned off, and I manhandled control
of rear wheels breaking loose
As you see, not once did EBCM command ABS even with rough road values and lataccel spikes

 

[teamzr1]

Here you can see I was pushing the steering hard and erratic, notice the bias in degrees
And the steering effort never got stiffer/harder, and if your problem was solely SWPS then you would feel it in steering wheel
as EBCM commands power steering fluid flow pressure changes

You should be able to do same type of testrun and see same type of results
I'd focus on EBCM and wiring

 

[teamzr1]

And few more PIDs compares

 

[clive f]

I had a friend round to help me solve this swps problem today who is an electronics expert, he read through all of the replies on here and set about trying to diagnose what’s going on with the car. So on the tech 2 today the voltage on the sensor was stuck on 4.6v, nothing would change this at all, this is different to what I’ve found before. We then plugged in the old swps and the voltage on this was the same 4.6v. Measuring the resistance in each sensor shows they should both be working fine, so I got under the back of the car and started wiggling the wires and plug going into the etbcm, suddenly the voltage on the swps is changing, so the fault appears to be in either the wiring to the plug or the pins, the analogue signal is shown in the manual as a light blue wire connecting to pin 23, all pins appeared to be in place and corrosion free wiggling the wire sent the volts back to 4.6 and no change, so something not right inside the etbcm? Taking my old etbcm that kept throwing abs faults, I removed the housing with the circuit board and plug on and managed to get it over the exhaust pipe to be close enough to the etbcm on the car so that we could plug this in instead to see if the problem still persisted. With the old one plugged in the swps voltage works fine , and this didn’t change no matter how many times we wiggled the plug or the wires, so I think we can safely assume that the fault is inside the etbcm and has been something slowly breaking down due to the previous erratic readings, every time the car has gone over a bump in the road it’s changed. So my expert detective mate has taken the old etbcm away with him, this was throwing the old abs error codes which we hope will be sorted by replacing the Bosch relays, there is a department where he works that builds and repairs circuit boards so fingers crossed once it’s repaired I can swap this one over for the one on the car without disturbing any of the brake lines in the other half of the unit , and all hopefully will be back to normal.

 

[clive f]

I’m having difficulty find these part numbers in the Uk, is there an alternative part number that does the same job?

 

[teamzr1]

Read the thread from Plastic Orange and I related to this
EBCM Relay

Pete I think bought six of these relays which are used on all C5s from 1999
They might look different but as long as they are normally open or closed (depending on what yours are) they should work

I would have preferred Pete having taken his ETBCM apart that should have replaced the old one but as been discussed
due to heat that it is common for those relays to decay and also soldering joints cracking that you might not see, so I would
suggest your friend reflow solder joints, replace the relays and assure all male and female pins are clean, not bent and the crimps
to the wiring pins are good.

Contact Pete, and maybe you can get with him to buy two from him or tell you where he bought his IF they are the same
contact state as to normally open or closed

You might find both your EBCMs have different issues and take relays from one to swap with the other, but re-solder joints on both.
Use good lighting to closely look at the joints, pins and crimps.

Keep in mind, GM has had nothing but trouble with the vendor in Japan that controls ALL wiring looms that faulty crimps of pins have been seen in all makes of GM vehicles.

If in doubt I pull the wiring out of connectors and using a crimp tool re-crimp to be sure tight connection to copper of wire.

I would consider since in 1997-98 the EBCM in ass end where water can be kicked up is protect the unit with some plastic, but enough airspace high to allow controller case to vent heat out.

Here is some of exact model number
relay

Now seeing the downside, this is a normal 4 connector relay, common used in GM should be able to find these easy
Pete's relays are different type of soldering pins, in a pinch though your friend should be able to make them solder in

How's this, right in your backdoor

UK Relays

If no avail getting relay, try Amazon, they have the 4 pin 12 volt relays

Amazon relays

 

[oelarse]

This should be the correct relay for 97-00 ABS units
I bought these of ebay to a spare ebcm I had

 

[plastic orange]

I bought 10 relays, so if anyone needs one, just ask. I know i should have replaced it, but re soldering sorted the issue, so that's for when or if it fails.

Pete

 

[clive f]

Thanks guys, surprised that I can’t get these in the uk and they no longer exist in the Bosch parts catalogue, Pete are yours the same part number as the ones in the photo? If so I’d gladly take two please and replace both

 

[plastic orange]

Thanks guys, surprised that I can’t get these in the uk and they no longer exist in the Bosch parts catalogue, Pete are yours the same part number as the ones in the photo? If so I’d gladly take two please and replace both

My relays aren't the same as the ones pictured - my car is a 2001 model. They are soldered into the board with I think 5 connections. If you check out the thread I started, then you'll see what my module looked like. If you do find they are of use, of course you can have some.

Pete

 

[oelarse]

This is how the relay for 01-04 cars looks like ( old and new one)

 

[plastic orange]

This is how the relay for 01-04 cars looks like ( old and new one)

View attachment 14400

View attachment 14401

Yes, that's what the ones I've bought look like