C4 diagnostic tool
- Thread starter mickdowd
- Start date
teamzr1
Supporting vendor
You did not say what years your C4 is but the DLC connector under the dash is going to be 12 pins but then in 1994-96 changed
to 16 pins
There is no way to connect a diagnostics tool or a OBD scanner without the correct cable that matches what the tool you have requires
as that is the network path to the ECM and CCM
Might buy just the cable from Snap On or maybe find one in searching cyberspace that has the correct DLC connector at one end
and the correct one for the tool at the other end
to 16 pins
There is no way to connect a diagnostics tool or a OBD scanner without the correct cable that matches what the tool you have requires
as that is the network path to the ECM and CCM
Might buy just the cable from Snap On or maybe find one in searching cyberspace that has the correct DLC connector at one end
and the correct one for the tool at the other end
teamzr1
Supporting vendor
87 the DLC is 12 pins
Also, most tools of that time require plugging into the cigarette lighter to supply voltage to the tool to function
Need to look at your tool and see what type of connector and amount of pins the ADLC cable needs
like is it a DB9, which is RS232 or a USB connector
Or uses a connector only that tool uses
Also, most tools of that time require plugging into the cigarette lighter to supply voltage to the tool to function
Need to look at your tool and see what type of connector and amount of pins the ADLC cable needs
like is it a DB9, which is RS232 or a USB connector
Or uses a connector only that tool uses
JonnyC4
CCCUK Member
It think the Snap on can't read your OBD1 codes. I use a Innova 3120F to read out the codes, this was recommended to my by some retired GM techs. It works fine.
You can also buy Gordon Killebrew's diagnostic code grounding plug kit, they are sometimes available on Ebay. Choose the green set from 1982-1993.
You can also buy Gordon Killebrew's diagnostic code grounding plug kit, they are sometimes available on Ebay. Choose the green set from 1982-1993.
Thank you Jonny, I will look for one of them
Where would I get one from?
teamzr1
Supporting vendor
That is an old analog tester and finding cables for it will be pretty hard
Snap-on PDM MT500 Precision Diagnostics Meter (PDM) is a highly versatile diagnostic test instrument specially designed for automobiles and light trucks. Numerous features have been incorporated into the design of the MT500 to make it accurate and easy to use.
These include: 10 Megaohm Minimum Input Impedance Numerous Test Ranges Color-coded Switch Positions & Test Lead Jacks Digital LCD Display Polarity Sensitive Test Leads Ignition and Fuel System Dwell / Duty Cycle Measurements in either degrees or percent Internal Battery for Portability. Mounted on rolling cart,
There are 4 jacks at bottom that the test leads go to mostly for looking at timing and dwell readings
This is not a OBD-I scanner and would not plug into the DLC
If not having a scanner there is a way to jumper 2 pins on the DLC and then on the dash it would flash a light you could to see what and if any error codes are present
Snap-on PDM MT500 Precision Diagnostics Meter (PDM) is a highly versatile diagnostic test instrument specially designed for automobiles and light trucks. Numerous features have been incorporated into the design of the MT500 to make it accurate and easy to use.
These include: 10 Megaohm Minimum Input Impedance Numerous Test Ranges Color-coded Switch Positions & Test Lead Jacks Digital LCD Display Polarity Sensitive Test Leads Ignition and Fuel System Dwell / Duty Cycle Measurements in either degrees or percent Internal Battery for Portability. Mounted on rolling cart,
There are 4 jacks at bottom that the test leads go to mostly for looking at timing and dwell readings
This is not a OBD-I scanner and would not plug into the DLC
If not having a scanner there is a way to jumper 2 pins on the DLC and then on the dash it would flash a light you could to see what and if any error codes are present
teamzr1
Supporting vendor
What you need is a OBD-I scanner and recorder
To us like this one, you install the software on a laptop that has MS Windows
Here is one I use and have my OBD-I tuning customers use
On the left, select the Datacat
On that page at the bottom, select the $134 one which is the scanner software and the 12 pin ADLC cable
This allows scanning the engine and auto tranny
Allows also to drive the C4 while scanner is in record mode which gets saved as a file and can be replayed later
and also email the recording to someone like me that can analyze the data and point to issues seen
To us like this one, you install the software on a laptop that has MS Windows
Here is one I use and have my OBD-I tuning customers use
On the left, select the Datacat
On that page at the bottom, select the $134 one which is the scanner software and the 12 pin ADLC cable
This allows scanning the engine and auto tranny
Allows also to drive the C4 while scanner is in record mode which gets saved as a file and can be replayed later
and also email the recording to someone like me that can analyze the data and point to issues seen
teamzr1
Supporting vendor
If just wanting to see what codes have tripped, can use like a paperclip or wire and jump 2 pins of DLC
If you jumper the "A" and "B" terminals, you should be able to see the check engine light "flash" the codes. It will start with one flash, followed by a short pause, then two quick flashes...this is code "12", which signals that the ECM is in diagnostic mode.
It will flash the individual codes three times, then move on to the next stored code. If there are no codes stored, the "12" code will flash repeatedly.
If you jumper the "A" and "B" terminals, you should be able to see the check engine light "flash" the codes. It will start with one flash, followed by a short pause, then two quick flashes...this is code "12", which signals that the ECM is in diagnostic mode.
It will flash the individual codes three times, then move on to the next stored code. If there are no codes stored, the "12" code will flash repeatedly.
teamzr1
Supporting vendor
You're chasing your tail that way as if the problem is random, you really need a OBD-I scanner so it can be in record mode and
if a problem occurs, the problem will be trapped in the recording data as what happened within the engine at the time
teamzr1
Supporting vendor
Does thus happen when engine is cold, hot, A/C on or off, in park, etc ?
What happens, simply ramps RPMs, dies, wants to stall out, etc ?
White or black smoke out the pipes when this happens ?
Does it happen when going decel ( lifting off gas pedal) coming to a stop ?
Engine stock ?
JonnyC4
CCCUK Member
It's like the paper clip story, but these make you do it safely. The green small booklet shows you what these codes mean. As Gordon Killebrew knows the system very well and was part of the C4 team, back in the days. He has even a school for repairing C4's.
With the kit you can count the lights that the service engine soon shows you.
I've bought my Innova via my work, but you can find them on Amazon and other websites.
Lewis Kingston
Well-known user
Out of curiosity, have you looked at the throttle body itself? When I had an intermittent erratic idle on my '86 C4, it was the fault of worn bushings in the throttle body. Quiet a common problem. The blades wouldn't close properly because of the wear in the bushings/shaft, and the engine would hunt or idle high as a result. If you grabbed the cable end of the shaft and gave it a wiggle, it'd usually settle back down – and the play would be quite obvious if you gave the end of the shaft a tweak, too.
Might just be worth checking, in any case.
Might just be worth checking, in any case.
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Only at idle, and not every time.