cruise control
Thread Starter
Heel & Toe
Joined: Mar 2008
Posts: 18
Likes: 0
From: lakeside california
cruise control
Hello everyone I have question about the possibility of there being a different PCM for cruise control.I changed out my PCM recently and now I have no cruise any suggestions?If not any ideas on cruise control trouble shooting? Thanks Patrick
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
You will get better response if you fill out your profile and at least tell us what year car you have, transmission etc.
Unless the replacement PCM was for a car with different transmission the change should not have caused the problem but since it is near the cruise servo (assuming a late C4) make sure you didn't accidentally disconnect a vacuum hose while changing it.
The next suggestion is to get a Factory Service Manual, it has step by step trouble shooting charts for nearly any problem and will likely cost less than one trip to a dealer for diagnosis.
Good luck, let us know what you find.
Unless the replacement PCM was for a car with different transmission the change should not have caused the problem but since it is near the cruise servo (assuming a late C4) make sure you didn't accidentally disconnect a vacuum hose while changing it.
The next suggestion is to get a Factory Service Manual, it has step by step trouble shooting charts for nearly any problem and will likely cost less than one trip to a dealer for diagnosis.
Good luck, let us know what you find.
Team Owner
Joined: Jan 2003
Posts: 20,316
Likes: 246
From: Summerland B.C. Canada
Thread Starter
Heel & Toe
Joined: Mar 2008
Posts: 18
Likes: 0
From: lakeside california
cruise control
Sorry it was late when i posted,I have a 85 with an auto transmission.Are the PCM's different for manual and auto? I have checked vacuum lines,disengage switch on the pedal and fuses.Is the VSS operate the speedometer as well?Also checked the linkage to the throttle body.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
As far as I know the ECM's are different for automatic and manual, I'm not sure if affects the cruise but as you can see from Agent 86's diagnostic chart the manual cars have use a clutch switch input that the auto doesn't have, so that could come into play.
The VSS operates both the speedometer and cruise so if the speedo is functioning that is probably not the problem.
I would imagine the diagnostics provided by Agent 86 should be close for your 85, I would try following the flow chart, good luck.
The VSS operates both the speedometer and cruise so if the speedo is functioning that is probably not the problem.
I would imagine the diagnostics provided by Agent 86 should be close for your 85, I would try following the flow chart, good luck.
