Have a Car Question? Ask a Mechanic Online.
Hello and good evening. You will need a scan tool to enable the relearn mode. Here is the procedure once you get that far.
IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.
IMPORTANT: If the crankshaft position (CKP) system variation learn procedure cannot be completed successfully, refer to DTC P1336 for additional diagnostic information.
Idle Learn Procedure Anytime the powertrain control module (PCM) or the battery is disconnected, the PCM loses power, or the PCM is reprogrammed, the PCMs learned idle position is lost. The engine idle is unstable when the learned idle position is lost.Perform the following procedure in order to return the learned idle to the correct position:Automatic Transmission
Your JA Expert,
So the vehicle will not run correctly until this is done? And basically only the GM dealer has a scanner that does this procedure right?
Snap on Scanners will allow this procedure. I am sure most of the upper scale scanners like OTC will do it as well. It will not run to its optimum until it is completed and it will set a code in memory as well until its done.
At first the truck ran extremely rough until it just wouldn't start. Bought scanner and had o2 codes as well as the crankshaft sensor. Replaced crankshaft sensor truck now starts but runs extremely rough and keeps stalling - won't idle. Assuming that is because of what u said above. Scanner is not getting the crankshaft code or any codes now, however have not ran the vehicle for more than a minute at most as it keeps stalling
You may have to use 2 feet to keep it running until this gets done. It is basically the procedure to sync the cam and crank sensors.
Also, Make sure you are not dealing with a dirty throttle plate as well. That can affect idle quality
Guess we may have to find a scanner with this capability, since ours does not seem to have the relearn function. Thanks
You are welcome. Once you find one, it may take 2 or 3 times for the vehicle to accept the procedure, so just be patient