Circuit Description
When the ignition switch turns ON, the Transmission Control Module (TCM) performs a 3-second POWER indicator bulb check. The TCM performs the bulb check by grounding the POWER indicator control circuit. The Power/Normal switch button grounds the shift mode signal circuit to the TCM when the Power/Normal switch sets to POWER. The above condition causes the TCM to ground the POWER indicator control circuit. Grounding the POWER indicator control circuit turns on the POWER indicator lamp located in the instrument panel gauge cluster. The POWER indicator informs the driver that the TCM is using the Power gear shift schedule (delaying upshifting for improved acceleration). The TCM dims the POWER indicator lamp by adding additional internal resistance to the POWER indicator control output circuit when both of the following conditions occur:
| • | The POWER indicator remains on. |
| • | The parking lamps/headlamp remain on. |
Dimming the POWER indicator lamp reduces excessive glare to the driver at night. The following conditions occur after the Power/Normal switch button sets to NORMAL:
- The Power/Normal switch button removes a path to ground to the shift mode signal circuit.
- The TCM turns off the POWER indicator lamp.
- The TCM uses the Normal gear shift schedule (early upshifting for improved fuel economy).
Diagnostic Aids
Inspect for the following conditions:
| • | An open POWER indicator lamp bulb filament. |
| • | An open IG COIL fuse |
| • | A faulty Power/Normal switch (always open) |
| • | A poor ground (G200) |
| • | An open circuit between the TCM and the instrument panel gauge cluster |
| • | A damaged instrument panel gauge cluster printed circuit |
| • | A faulty TCM |
The following conditions may cause an intermittent condition:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Before replacing components, inspect the inline harness connector terminals for the following conditions:
| • | Poor connections |
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Reduced terminal-to-wire connections. |
Repeat the OBD System Check after making repairs in order to ensure that the system functions normally.
Refer to Wiring Repairs in Wiring Systems when repairing any wiring.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The 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.
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This step verifies that the TCM performs the bulb check.
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This step tests the integrity of the indicator control circuit.
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This step inspects for an open bulb filament.
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This step tests the power source to the instrument panel gauge cluster.
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This step tests for an open in the indicator control circuit.
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This step determines if the TCM responds by turning on the POWER indicator when grounding the POWER signal circuit.
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This step tests for a reduced ground (G200) to the Power/Normal switch.
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This step tests for a faulty Power/Normal switch.
See the above figure.
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This step verifies if the condition relates to a poor connection and not due to a faulty TCM.
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This step tests for proper operation of the POWER indicator.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Did the POWER indicator lamp turn on for at least 3 seconds? | -- | |||
Does the POWER indicator lamp turn on? | -- | |||
Is the bulb filament open? | -- | |||
Does the test lamp turn on? | -- | |||
Use J 39200 in order to measure the resistance between the instrument panel gauge cluster harness connector C1 terminal 11 and the TCM harness connector terminal 8. Is the resistance less than the specified value? | 2 ohms | |||
Does the POWER indicator lamp remain on after the 3 second bulb check? | -- | |||
Does the test lamp turn on? | -- | |||
Use the J 39200 in order to measure the resistance across the Power/Normal switch terminals. Is the resistance less than the specified value in the P position? | 2 ohms (∞ with the Switch in the (N) position) | |||
Inspect the TCM connector for poor terminal contact. Replace the TCM if terminal contact is OK. Is the procedure complete? | -- | -- | ||
11 | Replace the POWER indicator bulb. Is the replacement complete? | -- | -- | |
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? | -- | -- | |
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? | -- | -- | |
14 | Repair the open or the high resistance in the PNK wire between the instrument panel gauge cluster and the TCM. Is the repair complete? | -- | -- | |
15 | Repair the open or the high resistance in the BLK wire between the Power/Normal switch harness connector terminal 4 and G200. Is the repair complete? | -- | -- | |
16 | Replace the Power/Normal switch. Refer to Power/Normal (P/N) Switch Replacement . Is the procedure complete? | -- | -- | |
17 | A malfunction does not exist at this time. Refer to Diagnostic Aids for additional information. Is the action complete? | -- | -- | |
Does the POWER indicator lamp turn on for approximately 3 seconds? (The indicator will remain ON with the Power/Normal switch in the Power (P) position). | -- | System OK |
