2nd Gear Start Switch and Indicator Lamp CKT Check

Diagnostic Chart:

Diagnostic Chart (cont'd):

CIRCUIT DESCRIPTION

NOTE: Refer to Automatic Transmission Controls - Cell 39, 2nd Gear Start Switch for the appropriate schematic.

The 2nd gear start switch enables the operator to select a 2nd gear start for increased traction in slippery driving conditions. When the operator selects 2nd gear, the second gear start switch input signal momentarily toggles to zero volts. The PCM then turns ON the 2nd gear start mode indicator lamp and de-energizes the 1-2 shift solenoid, enabling second gear. This 2nd gear start mode indicator lamp is located within the switch itself on Pontiacs and in the instrument cluster on Chevys.

During light and medium acceleration conditions, the vehicle starts in 2nd gear when second gear is selected. However, 2nd gear starts are overridden and 1st gear starts occur if a hard acceleration condition (wide open throttle) is requested. Normal 1st gear start mode is obtained by toggling the 2nd gear start switch again, or when the ignition switch is cycled OFF then ON.


DIAGNOSTIC AIDS

If the electrical circuit checks are OK and 2nd gear starts are not correct, then a mechanical/hydraulic malfunction might exist. Refer to Automatic Transmission / System Diagnosis.


TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic chart.

1. Step 1 tests the second gear start switch circuits.

2. Step 2 tests for a faulty 2nd gear start switch.

4. Step 4 tests for a voltage input from the PCM to the 2nd gear start switch.

6. Step 6 tests for a voltage input from the fuse to the 2nd gear start switch.

8. Step tests for a faulty indicator lamp circuit within the 2nd gear start switch.