Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
A scan tool can clear the MIL/DTC.
The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

DTC P1779

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check - Engine Controls?	-	Go to Step 2	Go to DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS
2	Install a scan tool. Turn ON the ignition with the engine OFF. IMPORTANT: Before clearing the DTC, use the scan tool in order to record the ECM Freeze Frame and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Freeze Frame and Failure Records from the ECM and the TCM. Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the ECM and TCM. Record the DTC Failure Records. Did you record any ECM Failure Records?	-	Go to DIAGNOSTIC TROUBLE CODE DEFINITIONS	Go to Step 3
3	Clear the DTC. Turn the ignition OFF for at least 30 seconds. Start, and allow the engine to idle. Did DTC P1779 reset?	-	Go to Step 4	Go to INTERMITTENTS
4	Did any other DTCs set?	-	Go to DIAGNOSTIC TROUBLE CODE DEFINITIONS	Go to Step 5
5	Replace the ECM. Refer to ENGINE CONTROL MODULE . Is the action complete?	-	Go to Step 6	-
6	Perform the following operation to verify the repair: Select DTC on the scan tool. Select Clear Info. Start, and idle the engine. Select Specific DTC. Enter DTC P1779. Does the DTC reset?	-	Go to Step 2	Go to Step 7
7	With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed?	-	Go to DIAGNOSTIC TROUBLE CODE DEFINITIONS	System OK