B2105

B2105-IGNITION UNLOCK RUN/START CONTROL CIRCUIT HIGH





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the ignition on or off and with the FCM awake.

- Set Condition:
The Front Control Module will set this DTC within 2 seconds if the ignition unlock run/start circuit voltage is not what the expected value should be.





Theory of Operation

The (F942) Fused Ignition Switch Output circuit supplies the FCM with battery power. The FCM processes the input and sends it out as the (F1) Fused Ignition Switch Output circuit to the Shift Lever assembly (3.7L or 6.1L) or the PCM (except 3.7L or 6.1L).

Diagnostic Test

1. CHECK FOR ACTIVE DTC
With the scan tool, read the active DTC's.
Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 10 seconds then turn the ignition off.
With the scan tool, read the active DTC's.
Does the scan tool display this DTC as active?

Yes

- Go To 2

No

- If the DTC is stored, check for an intermittent condition. Using the wiring diagram/schematic as a guide, visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

2. DETERMINE ENGINE SIZE
Is this vehicle equipped with a 3.7L or 6.1L engine?

Yes

- Go To 3

No

- Go To 6

3. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT SHORTED TO VOLTAGE




Disconnect the Shift Lever Assembly harness connector.
Cycle the ignition switch from off to on then back to off.

NOTE: The ignition switch must be in the off position when performing the following step.

Using a 12-volt test light connected to ground, check the (F1) Fused Ignition Switch Output (Run Start) circuit.
Does the test light illuminate brightly?

Yes

- Repair the (F1) Fused Ignition Switch Output (Run Start) circuit for a short to voltage.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

No

- Go To 4

4. SHIFT LEVER ASSEMBLY




Turn the ignition on.
With the test light still connected from the previous step, check the (F1) Fused Ignition Switch Output (Run Start) circuit.
Does the test light illuminate brightly?

Yes

- Replace the Shift Lever Assembly.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

No

- Go To 5

5. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT OPEN




Turn the ignition off.
Remove the FCM from the Integrated Power Module.
Measure the resistance of the (F1) Fused Ignition Switch Output (Run Start) circuit between the Shift Lever Assembly and the FCM-IPM connector.
Is the resistance below 5.0 ohms?

Yes

- Inspect the wiring and connectors for damage or shorted circuits. If ok, replace and program the Front Control Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

No

- Repair the (F1) Fused Ignition Switch Output (Run Start) circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

6. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT SHORTED TO VOLTAGE




Disconnect the Powertrain Control Module C1 harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Cycle the ignition switch from off to on then back to off.

NOTE: The ignition switch must be in the off position when performing the following step.

Using a 12-volt test light connected to ground, check the (F1) Fused Ignition Switch Output (Run Start) circuit.
Does the test light illuminate brightly?

Yes

- Repair the (F1) Fused Ignition Switch Output (Run Start) circuit for a short to voltage.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

No

- Go To 7

7. POWERTRAIN CONTROL MODULE




Turn the ignition on.
With the test light still connected from the previous step, check the (F1) Fused Ignition Switch Output (Run Start) circuit.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Does the test light illuminate brightly?

Yes

- Replace the Powertrain Control Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 8

8. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT OPEN




Turn the ignition off.
Remove the FCM from the Integrated Power Module.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (F1) Fused Ignition Switch Output (Run Start) circuit between the Powertrain Control Module C1 connector and the FCM-IPM connector.
Is the resistance below 5.0 ohms?

Yes

- Inspect the wiring and connectors for damage or shorted circuits. If ok, replace and program the Front Control Module.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Repair the (F1) Fused Ignition Switch Output (Run Start) circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.