Overdrive Off Indicator Inoperative. Chevrolet Joy 2008

For 1990-2009 cars

### Circuit Description

Within the ignition switch in the ON position, voltage is applied to the O/D switch. Whenever the overdrive switch, located next to the shifter; is depressed (switch contacts closed), system voltage is applied through the closed contacts of the overdrive switch to the transmission control module (TCM) and the O/D lamp. When this occurs, the OD/OFF indicator light in the instrument cluster will illuminate and the transmission control module (TCM) will simultaneously receive a voltage signal at the O/D input. With a voltage input, the TCM will disable the overdrive function. When the overdrive switch is depressed again, the overdrive switch opens. When this occurs, the O/D/OFF indicator light in the instrument cluster will go out and the voltage signal to the TCM O/D input will be removed. With a high voltage input, the TCM will disable the overdrive function and the transaxle will not be permitted to shift into overdrive.

### Diagnostic Aids

Inspect for the following conditions:

• | Open fuse

• | Poor connections at any in line harness connectors

• | Loose ground connections

An intermittent may be caused by the following conditions:

• | A poor connection

• | Rubbed through wire insulation

Inspect the wiring. If any wiring repairs are necessary, refer to Wiring Repairs .

### Test Description

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

1. This step checks the overdrive switch by jumping the switch to B+.

2. This step checks the lamp control circuit for an open circuit.

3. This step checks the O/D OFF indicator.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Automatic Transmission Controls Schematics
1 | Did you perform the Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Automatic Transmission

2

1. Disconnect the overdrive switch.
2. Connect a 3A fused jumper between the switch terminals.
3. Turn ON the ignition switch with the engine OFF.

Did the O/D OFF indicator illuminate?

Go to Step 7

Go to Step 3

3

1. Turn OFF the ignition.
2. Connect 3A fused jumper between the switch connector lamp control circuit and B+.

Does the test lamp illuminate?

Go to Step 6

Go to Step 4

4 | Backprobe with 3A fused jumper between the instrument cluster connector at the lamp control circuit and B+. Does the test lamp illuminate? | Go to Step 5 | Go to Step 8
5 | Repair an open circuit in the lamp control circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 9 | --
6 | Repair an open circuit in the switch ignition feed circuit. Refer to Wiring Repairs . | Go to Step 9 | --
7 | Replace the overdrive switch. Did you complete the replacement? | Go to Step 9 | --
8 | Replace the instrument panel cluster (IPC). Refer to Instrument Cluster Replacement . Did you complete the replacement? | Go to Step 9 | --

9

1. Turn the ignition switch to LOCK.
2. Reconnect all disconnected connectors.
3. Turn the ignition switch to the ON position.
4. Press and release the overdrive switch while observing the O/D OFF indicator.

Does the O/D OFF indicator light toggle from on to OFF.

System OK

Go to Step 2