P1801

P1801, P1811 Power Supply Circuit for Transfer Control Unit

Description

The transfer control unit controls the transfer control device which controls shifts between 4H and 4LO and between 2WD and 4WD. When the vehicle battery is removed, the power supply to the transfer control unit is interrupted, and self-diagnosis memory function is suspended. These DTCs may also set when the power supply voltage for the transfer control unit is abnormally low while driving.

DTC Logic

DTC Detection Logic






DTC Confirmation Procedure

1. DTC CONFIRMATION PROCEDURE

1 Turn ignition switch ON.
2 Perform "DTC check".

Are DTCs "P1801 or P1811 detected?
YES
Perform diagnosis procedure. Refer to "Diagnosis Procedure".
NO
Inspection End.

Diagnosis Procedure

Regarding Wiring Diagram information, refer to [Transfer Control Unit: Wiring Diagram] [1][2]Electrical Diagrams.

1. CHECK POWER SUPPLY

1 Turn ignition switch "OFF". (Stay for at least 5 seconds.)
2 Disconnect transfer control unit harness connector.
3 Check voltage between transfer control unit harness connector terminals and ground.











4 Turn ignition switch "ON". (Do not start engine.)





5 Check voltage between transfer control unit harness connector terminals and ground.






Is there voltage?
YES
GO TO 2.
NO
Check the following. If any items are damaged, repair or replace damaged parts.

- 40 A fuse (No. J, located in the fuse and fusible link box).
- 10 A fuses (No. 18, located in the fuse block (J/B) and Nos. 57 and 58 located in the fuse and relay box).
- Harness for short or open between battery and transfer control unit harness connector M152 terminal 19.
- Harness for short or open between battery and transfer shut off relay 2 harness connector E157 terminal 1 and 3.
- Harness for short or open between battery and transfer shut off relay 1 harness connector E156 terminal 3.
- Harness for short or open between ignition switch and transfer control unit harness connector M152 terminal 25.
- Harness for short or open between ignition switch and transfer shut off relay 1 harness connector E156 terminal 1.
- Harness for short or open between transfer shut off relay 2 harness connector E157 terminal 5 and transfer control unit harness connector M153 terminals 44, 45.
- Harness for short or open between transfer shut off relay 1 harness connector E156 terminal 5 and transfer control unit harness connector M153 terminals 44, 45.
- Harness for short or open between transfer shut off relay 2 harness connector E157 terminal 2 and transfer control unit harness connector M153 terminal 40.
- Harness for open between transfer shut off relay 1 harness connector E156 terminal 2 and ground.
- Battery and ignition switch.
- Transfer shut off relay 1, 2. Refer to "Component Inspection".

2. CHECK GROUND CIRCUIT

1 Turn ignition switch "OFF".
2 Disconnect transfer control unit harness connector.
3 Check continuity between transfer control unit harness connector M152 terminals 6 (M/T models) and 18, and M153 terminal 32 and ground.











Also check harness for short to power.

Do you have continuity?
YES
GO TO 3.
NO
Repair open circuit or short to power in harness or connectors.

3. CHECK TRANSFER CONTROL UNIT

Check transfer control unit input/output signal. Refer to [Transfer Control Unit: Reference Value] Pinout Values and Diagnostic Parameters.

Are the inspection results normal?
YES
GO TO 4.
NO
Check transfer control unit pin terminals for damage or loose connection with harness connector. If any items are damaged, repair or replace damaged parts.

4. CHECK DTC

Drive vehicle and then perform "DTC check".

Do DTCs P1801 or P1811 display?
YES
Replace transfer control unit. Refer to [Transfer Control Unit: Removal and Installation] Service and Repair.
NO
Inspection End.

Component Inspection

1) Turn ignition switch "OFF". (Stay for at least 5 seconds.)
2) Remove transfer shut off relay 1 and transfer shut off relay 2. Refer to [P1801, P1811 Power Supply Circuit for Transfer Control Unit].
3) Apply 12 V direct current between transfer shut off relay terminals 1 and 2.





4) Check continuity between relay terminals 3 and 5.






5) If inspection results are not normal, replace the transfer shut off relay 1 or 2.