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P188C




Four Wheel Drive (4WD) Systems

Pinpoint Test D: DTCs P188C and P188D

Normal Operation

The active, on-demand AWD (All-Wheel Drive) system uses data from other systems as inputs to the PCM. The PCM uses the inputs to determine the appropriate duty cycle to send to the AWD (All-Wheel Drive) relay module over hardwired command/control circuit and returns information over the feedback/monitor circuit.

- DTC P188C (AWD (All-Wheel Drive) Relay Module Communication Circuit)- When the PCM detects an open, a short to ground or voltage on the command circuit, this DTC is set and the AWD (All-Wheel Drive) relay module may not allow All-Wheel Drive (AWD) operation.

- DTC P188D (AWD (All-Wheel Drive) Relay Module Feedback Circuit)- When the PCM detects an open, a short to ground or voltage on the feedback circuit, this DTC is set and the AWD (All-Wheel Drive) relay module may not allow All-Wheel Drive (AWD) operation.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- AWD (All-Wheel Drive) Relay Module

- PCM

PINPOINT TEST D : DTCs P188C AND P188D

NOTE: Carry out a thorough inspection and verification as outlined before carrying out this pinpoint test. Refer to Inspection and Verification. Four Wheel Drive (4WD) Systems

D1 CHECK THE AWD (All-Wheel Drive) RELAY MODULE FOR VOLTAGE

- Ignition OFF.

- Disconnect: AWD (All-Wheel Drive) Relay Module C4379.

- Ignition ON.

- Measure the voltage between AWD (All-Wheel Drive) Relay Module C4379-1, circuit CBB70 (YE-BU), harness side and the AWD (All-Wheel Drive) Relay Module C4379-4, circuit GD151 (BK-GN), harness side.






Is the voltage greater than 10 volts?

Yes
GO to D3.

No
GO to D2.

D2 CHECK THE AWD (All-Wheel Drive) RELAY MODULE VOLTAGE SUPPLY CIRCUIT

- Measure the voltage between AWD (All-Wheel Drive) Relay Module C4379-1, circuit CBB70 (YE-BU), harness side and chassis ground.






Is the voltage greater than 10 volts?

Yes
REPAIR circuit GD151 (BK/GN) for an open. CLEAR the DTCs. REPEAT the self-test.

No
VERIFY BJB (Battery Junction Box) fuse 70 (10A) is OK. If fuse is OK, REPAIR circuit CBB70 (YE-BU) for an open. If BJB (Battery Junction Box) fuse is not OK, REFER to the Wiring Diagrams to identify possible causes of the circuit short [1][2]Diagrams By Number. CLEAR all CMDTCs (Continuous Memory Diagnostic Trouble Codes). REPEAT the self-test.

D3 CHECK THE AWD (All-Wheel Drive) RELAY MODULE CONTROL AND FEEDBACK CIRCUITS FOR A SHORT TO VOLTAGE

- Ignition OFF.

- Disconnect: PCM C175B.

- Ignition ON.

- Measure the voltage between AWD (All-Wheel Drive) Relay module C4379-3, circuit VCF35 (GN), harness side and chassis ground; and between AWD (All-Wheel Drive) Relay Module C4379-6, circuit VCF34 (WH), harness side and chassis ground.






Is any voltage present?

Yes
REPAIR the affected circuit(s) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.

No
GO to D4.

D4 CHECK THE AWD (All-Wheel Drive) RELAY MODULE CONTROL AND FEEDBACK CIRCUITS FOR A SHORT TO GROUND

- Ignition OFF.

- Measure the resistance between AWD (All-Wheel Drive) Relay module C4379-3, circuit VCF35 (GN), harness side and chassis ground; and between AWD (All-Wheel Drive) Relay Module C4379-6, circuit VCF34 (WH), harness side and chassis ground.






Are the resistances greater than 10,000 ohms?

Yes
GO to D5.

No
REPAIR the affected circuit(s) for a short to ground. CLEAR the DTCs. REPEAT the self-test.

D5 CHECK THE AWD (All-Wheel Drive) RELAY MODULE CONTROL AND FEEDBACK CIRCUITS FOR AN OPEN

- Measure the resistance between AWD (All-Wheel Drive) Relay module, harness side and PCM, harness side as follows:

- AWD Relay module Connector-Pin Circuit PCM Connector-Pin C4379-3 VCF35 (GN) C175B-54 C4379-6 VCF34 (WH) C175B-3





Are the resistances less than 5 ohms?

Yes
GO to D6.

No
REPAIR the affected circuit(s) for an open. CLEAR the DTCs. REPEAT the self-test.

D6 CHECK THE AWD (All-Wheel Drive) RELAY MODULE CONTROL AND FEEDBACK CIRCUITS A SHORT TOGETHER

- Measure the resistance between AWD (All-Wheel Drive) relay module, C4379-3, circuit VCF35 (GN), harness side and AWD (All-Wheel Drive) relay module C4379-6, circuit VCF34 (WH), harness side.






- Repeat this measurement while wiggling the harness.

Is the resistance greater than 10,000 ohms?

Yes
GO to D7
No
REPAIR the affected circuit(s) for a short together. CLEAR the DTCs. REPEAT the self-test.

D7 CHECK FOR CORRECT AWD (All-Wheel Drive) RELAY MODULE OPERATION

- Ignition OFF.

- Check PCM C175B and AWD (All-Wheel Drive) Relay Module C4379 harness and component side connectors for:
- corrosion.

- pushed-out/bent pins.


- Connect: AWD (All-Wheel Drive) relay module C4379.

- Connect: PCM C175B.

- Ignition ON.

- CLEAR the DTCs. REPEAT the self-test.

- Operate the system and verify if the concern is still present.

Is the concern still present?

Yes
INSTALL a new AWD (All-Wheel Drive) relay module. REFER to All Wheel Drive (AWD) Relay Module Service and Repair. CLEAR the DTCs. REPEAT the self-test.

If DTC P188C or P188D is retrieved again, INSTALL a new PCM.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.

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