For 1990-2009 cars

### Circuit Description

When the ignition switch turns ON, the Powertrain Control Module (PCM) performs a 3-second OD/OFF indicator bulb check. The PCM performs the bulb check by grounding the OD/OFF indicator control circuit. The OD switch button grounds the OD/OFF signal circuit to the PCM when the OD switch button releases. The above condition causes the PCM to ground the OD/OFF indicator control circuit. Grounding the OD/OFF indicator control circuit turns on the OD/OFF indicator lamp located in the instrument panel gauge cluster. The OD/OFF indicator informs the driver that the transmission will not shift into overdrive (4th gear). The PCM dims the OD/OFF indicator lamp by adding additional internal resistance to the OD/OFF indicator control output circuit when both of the following conditions occur:

• | The OD/OFF indicator remains on.

• | The parking lamps/headlamps remain on.

Dimming the OD/OFF indicator lamp reduces excessive glare to the driver at night. The following conditions occur after the OD switch button is pressed:

1. The depressed OD switch button removes a path to ground to the OD/OFF signal circuit.
2. The PCM turns off the OD/OFF indicator lamp.
3. The PCM adds overdrive (4th gear) to the shift schedule.

### Diagnostic Aids

Inspect for the following conditions:

• | An open OD/OFF indicator lamp bulb filament

• | An open IG COIL fuse

• | A faulty OD switch (always open)

• | A reduced ground (G200)

• | An open circuit between the PCM and the instrument panel gauge cluster

• | A damaged instrument panel gauge cluster printed circuit

• | A faulty PCM

The following conditions may cause an intermittent condition:

• | A reduced connection

• | Rubbed through wire insulation

• | A broken wire inside the insulation

Before replacing components, inspect the inline harness connector terminals for the following conditions:

• | Reduced connections

• | Backed out terminals

• | Improper mating

• | Broken locks

• | Improperly formed or damaged terminals

• | Reduced terminal-to-wire connections

Repeat the Powertrain OBD System Check after making repairs in order to ensure that the system functions normally.

Refer to Wiring Repairs in Wirng Systems when repairing any wiring.

### Test Description

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

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. The scan tool creates an electronic copy of the data taken when the fault occurred. The information then stores in the scan tool for later reference.

2. This step verifies that the PCM performs the bulb check.

3. This step tests the integrity of the indicator control circuit.

4. This step inspects for an open bulb filament.

5. This step tests the power source to the instrument panel gauge cluster.

6. This step tests for an open in the indicator control circuit.

7. This step verifies if the PCM responds by turning on the OD/OFF indicator when grounding the OD/OFF signal circuit.

8. This step tests for a reduced ground (G200) to the OD switch.

9. This step tests for a faulty OD switch.

10. This step tests if the condition relates to a poor connection and is not due to a faulty PCM.

11. This step tests for proper operation of the OD/OFF indicator.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
2 |

1. Turn the OD switch to the released ON position.
2. Turn ON the ignition switch.

Did the OD/OFF indicator lamp turn on for at least 3 seconds?

--

Go to Step 7

Go to Step 3

3 |

1. Turn the ignition switch to the LOCK position.
2. Connect a fused jumper between ground and the PCM harness connector C3 terminal 6.
3. Turn the ignition switch to the ON position.

Does the OD/OFF indicator lamp turn on?

--

Go to Step 10

Go to Step 4

4 |

1. Turn the ignition switch to the LOCK position.
2. Remove the instrument panel gauge cluster.
3. Remove the OD/OFF indicator bulb from the cluster.

Is the bulb filament open?

--

Go to Step 11

Go to Step 5

5 |

1. Disconnect the instrument panel gauge cluster connector C3.
2. Turn the ignition switch to the ON position.
3. Connect a test lamp between ground and the instrument panel gauge cluster harness connector C3 terminal 11.

Does the test lamp turn on?

--

Go to Step 6

Go to Step 12

6 | Use J 39200 in order to measure the resistance between the instrument panel gauge cluster harness connector C3 terminal 13 and the PCM harness connector C3 terminal 6. Is the resistance less than the specified value? | 2 ohms | Go to Step 13 | Go to Step 14
7 |

1. Turn the ignition switch to the LOCK position.
2. Connect a fused jumper wire between ground and the PCM harness connector C3 terminal 2 by backprobing.
3. Turn the ignition switch to the ON position.

Does the OD/OFF indicator lamp remain on after the 3-second bulb check?

--

Go to Step 8

Go to Step 10

8 |

1. Turn the ignition switch to the LOCK position.
2. Disconnect the OD switch.
3. Connect a test lamp between B+ and the OD switch connector 1.

Does the test lamp turn on?

--

Go to Step 9

Go to Step 15

9 | Use J 39200 in order to measure the resistance across the OD switch terminals. Is the resistance less than the specified value with the switch released? | 2 ohms (∞ with the switch pressed) | Go to Step 17 | Go to Step 16
10 | Inspect the PCM connector C3 for reduced terminal contact. Replace the PCM if terminal contact is OK. Is the procedure complete? | -- | Go to Step 18 | --
11 | Replace the OD/OFF indicator bulb. Is the replacement complete? | -- | Go to Step 18 | --
12 | Repair the open or the high resistance in the BLK/WHT wire between the instrument panel gauge cluster and the IG COIL fuse. Is the repair complete? | -- | Go to Step 18 | --
13 | Inspect the instrument panel gauge cluster printed circuit for cracks or opens. Replace the instrument panel gauge cluster as necessary. Is the procedure complete? | -- | Go to Step 18 | --
14 | Repair the open or the high resistance in the WHT/BLK wire between the instrument panel gauge cluster and the PCM. Is the repair complete? | -- | Go to Step 18 | --
15 | Repair the open or the high resistance in the BLK wire between the OD switch harness connector terminal 1 and G200. Is the repair complete? | -- | Go to Step 18 | --
16 | Replace the OD switch. Refer to O/D Cut Switch Replacement . Is the procedure complete? | -- | Go to Step 18 | --
17 | A malfunction does not exist at this time. Refer to Diagnostic Aids for additional information. Is the action complete? | -- | Go to Step 18 | --
18 |

1. Turn the ignition switch to the LOCK position.
2. Reconnect the connector(s).
3. Turn the ignition switch to the ON position.

Does the OD/OFF indicator lamp turn on for approximately 3 seconds?

(The indicator will remain ON with the OD switch released).

--

System OK

Go to Step 1