Clearing Trouble Codes

The following procedures are provided for use with a Rotunda New Generation STAR (NGS) Tester. For procedures using a generic scan tool, refer to Powertrain Management/Computers and Control Systems.

PCM Reset Mode

The PCM reset mode provides a means for the NGS to command the powertrain control module (PCM) to clear all DTCs. When resetting the PCM, a DTC P1000 will be set in the PCM until all OBDII system or components have been monitored during the OBDII Drive Cycle. When a PCM reset is performed the following occurs:

a. DTCs cleared.
b. Freeze Frame Data cleared.
c. Oxygen sensor Test Data cleared.
d. Status of the OBDII System Monitors reset.
e. DTC P1OOO set.

Performing PCM Reset

1. Perform visual inspection and vehicle preparation as required.

2. Select "Vehicle and Engine Selection" menu.

3. Select year, engine, model with the appropriate qualifier if needed, for example, transmission or 49 state/Cal.

4. Select "Generic OBDII Functions" menu.

5. Select "Clearing ALL Codes."

6. Follow operating instructions from the NGS menu screen.

7. Perform OBDII Drive Cycle - Clear DTC P1000.

Clearing DTC P1000

In some localities it may become a legal requirement to pass an Inspection/Maintenance (I/M) test of the OBDII system. If the vehicle's powertrain system or its battery has just been serviced, the OBDII system is reset to a not ready for I/M testing condition. To prepare the vehicle for the test and to clear the DTC No. P1000, an OBDII Drive Cycle must be performed.

OBDII Drive Cycle

The following steps must be run in the order shown. If Steps 2, 3, or 4 are interrupted, repeat the step before proceeding. Any safe driving mode is acceptable between steps.

Always drive vehicle in a safe manner according to traffic conditions and obey all traffic laws.

1. Start engine and drive vehicle in typical city stop-and-go traffic for at least 10 minutes after it has reached normal operating temperature.

2. Idle vehicle for at least 45 seconds, then accelerate at part throttle to near 72 km/h (45 mph).

3. Cruise and maintain a select speed in the range of 48-64 km/h (30 to 40 mph) on a level road with throttle held steady for at least one minute.

4. Drive to accumulate at least four minutes in the range of 32-72 km/h (20 to 45 mph). If stop-and-go conditions occur, the accumulated time must be within the 32-72 km/h (20 to 45 mph) range. No wide open throttle (WOT) conditions should be encountered.

5. Decelerate and idle for at least 10 seconds.

6. Accelerate to approach 88 km/h (55 mph) at 1/2 throttle (elapsed time is about 10 seconds).

7. Cruise and maintain select speed in the range of 64-104 km/h (40 to 65 mph) on a level road with throttle held steady for at least one minute and 20 seconds.

8. OBDII Drive Cycle has been completed.