Shift Light: Testing and Inspection

Chart C-8B:

Chart C-8B Wiring Diagram:

CIRCUIT DESCRIPTION:

The 1-4 upshift relay is energized when the ECM grounds CKT 108, which provides battery voltage to the 1-4 upshift solenoid and activates it. When the solenoid (located in the transmission) is activated, it mechanically locks out the transmission linkage from being shifted from 1st gear to 2nd or 3rd gears. Under certain low load conditions the vehicle can only be shifted from 1st to 4th gear to improve fuel economy.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. A mechanical transmission problem is indicated if the transmission can only be put in 1st or 4th gear in this step.

2. Grounding the diagnostic terminal with the ignition "ON" and the engine not running, will energize the 1-4 upshift relay and solenoid indicating normal system operation.

NOTE:

Do not keep the diagnostic terminal grounded for more than 1 minute, as damage to the upshift solenoid may occur.

3. If the fuse for CKT 75 is blown, check circuit 438 for a short to ground.