For 1990-2009 cars

# Info - Intermittent Communication or Serial Data DTC Codes Stored in History

Subject: | Intermittent Communication or Serial Data DTC Codes Stored in History

Models: | 1997-2002 Chevrolet Malibu

| 1999-2002 Oldsmobile Alero

| 1997-1999 Oldsmobile Cutlass

| 1999-2002 Pontiac Grand Am

| with 3.1L or 3.4L Engine (VINs J, M, E -- RPOs LG8, L82, LA1)

### Ignition Switch Usage

It is possible to set a Serial Data DTC Code with improper usage of the ignition switch. On the above vehicles, if the ignition key is held between the ACCESSORY and ON position for over 5 seconds, and then rotated to ON and START sequentially, it is possible to set various DTC codes. The customer may see an illuminated Service Engine Soon, ABS and/or ETS OFF (Electronic Traction System) telltale. The next time the ignition switch is cycled, any set DTC codes will be stored in history and any telltales will be turned off.

Important: If the above condition is encountered and the ETS OFF and ABS lights are illuminated, the ABS and ETS systems will be deactivated for that key cycle. Normal functioning of these systems will resume with the next key cycle.

### Why Does This Happen?

If the ignition switch is held between the ACCESSORY and ON detent positions, it is possible to find a spot where the Ignition 1 input will be lost. If this condition remains for over 5 seconds, the PCM will interpret the loss of that signal as a communication fault and set an appropriate DTC code.

### How to Resolve This Issue

• | Instruct the customer on the proper operation of the ignition switch.

• | Instruct the customer not to "fiddle" with the switch. Actions such as slowly turning the key in order to see what instrument panel displays light in what order should be discouraged.

• | Do not attempt to hold the switch between detent positions.

• | Assure the customer that no fault exists in the vehicle and that under normal operating conditions, this concern should not reappear.

• | There are no possible software changes that will prevent the above condition.

• | Do not attempt to replace the ignition switch to remedy this condition.

• | You may clear the history codes to eliminate any later diagnostic confusion. Refer to the Tech 2 Diagnostic Scan Tool Operating Manual for specific instructions on clearing history codes.

| Important: Do not attempt any repairs on the vehicle to remedy this condition.