Power Indicator Remains Lit

Diagnostic Chart:

Description:

Wiring Diagram:

Circuit Description

When the ignition switch is turned to the ON position, the Powertrain Control Module (PCM) performs a three second POWER indicator bulb check by ground the POWER indicator control circuit during such period. When the Power/Normal switch is set to Power (P), it grounds the shift mode signal circuit to the PCM. This causes the PCM to ground the POWER indicator control circuit, turning on the POWER indicator lamp located in the I/P gage cluster. This indicator informs the driver that the PCM is using the Power gear shift schedule (delaying up shifting for improved acceleration). When this indicator is on and parking lamps/headlamps are turned on, the PCM dims the POWER indicator lamp by adding additional internal resistance to the POWER indicator control output circuit. This reduces excessive glare to the driver from the POWER indicator lamp at night. When the Power/Normal switch is set to Normal (N), it removes a path to ground to the shift mode signal circuit. Then, the PCM turns off the POWER indicator lamp and the PCM uses the Normal gear shift schedule (early upshifting for improved fuel economy).


Diagnostic Aids

Check for the following:

- Short to ground in the POWER indicator control circuit between the PCM and the I/P gage cluster.

- Short to ground in the shift mode signal circuit between the Power/Normal switch and the PCM.

- Faulty Power/Normal switch (staying closed at all times).

- Faulty PCM.

An intermittent condition may be caused by a rubbed through wire insulation. After repairs have been made, repeat the Powertrain OBD System Check to ensure the system is functioning normally.

If any wiring repairs need to be made, refer to Repair Procedures in Diagrams/Electrical.

Test Description

Numbers below refer to the circled numbers on the diagnostic chart.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Checks for a short to ground in the POWER indicator circuit.

3. Checks whether the condition is caused by a short to ground or a constantly-closed Power/Normal switch and not due to a faulty PCM (Figure 20).

4. Checks whether the condition is caused by a short to ground in the shift mode signal circuit and not due by a faulty Power/Normal switch (staying closed at all times).

9. Checks for proper operation of the POWER indicator.