Diagnosis Item 4: Diagnose shorts between CAN_H and L lines. <LHD>

caution

When servicing a CAN bus line, earth yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.

TROUBLE JUDGEMENT

When all of the following conditions are met, the M.U.T.-III determines that a short circuit is present between CAN_L and CAN_H lines.

The M.U.T.-III cannot receive the periodic transmission data from any ECUs.
The voltage between CAN bus lines (CAN_L and CAN_H lines) is 1.0 V or more, 4.0 V or less.
The resistance at CAN bus line (CAN_L and CAN_H lines) is 2 Ω or less.

TROUBLESHOOTING HINTS

Malfunction of the wiring harness
Malfunction of the connector
Malfunction of the ETACS-ECU
Malfunction of the combination meter
Malfunction of the transfer-ECU <4WD (6M/T, A/T)>
Malfunction of the A/C-ECU <Vehicles with automatic A/C>
Malfunction of the KOS&OSS-ECU <Vehicles with KOS&OSS>
Malfunction of the SRS-ECU
Malfunction of the ABS-ECU <Vehicles with ABS>
Malfunction of the ASTC-ECU <Vehicles with ASTC>
Malfunction of the steering wheel sensor <Vehicles with ASTC>
Malfunction of the A/T-ECU <A/T>
Malfunction of the engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: joint connector (CAN1)

caution

The strand end of the twist wire should be within 10 cm from the connector. For details refer to service precautions.

When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.

Q. Is the check result normal?

Go to Step 2.

Repair the defective connector.

STEP 2. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at its female-side intermediate connector (at the front wiring harness side).

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.7 and 18
OK: 120 ± 20 Ω

Q. Is the check result normal?

	<Within 120 ± 20 Ω> Go to Step 12.

	<Not within 120 ± 20 Ω> Go to Step 3.

STEP 3. Connector check: joint connector (CAN2)

caution

The strand end of the twist wire should be within 10 cm from the connector. For details refer to service precautions.

When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.

Q. Is the check result normal?

Go to Step 4.

Repair a defective connector or replace the joint connector.

STEP 4. Resistance measurement at joint connector (CAN2).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN2), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN2) terminal Nos.10 and 21
OK: 120 ± 20 Ω

Q. Is the check result normal?

	YES <Vehicles with KOS&OSS> : <Within 120 ± 20 Ω> Go to Step 6.

	YES <Vehicles without KOS&OSS and with ABS or ASTC> : <Within 120 ± 20 Ω> Go to Step 8.

	YES <Vehicles without KOS&OSS, ABS and ASTC> : <Within 120 ± 20 Ω> Go to Step 10.

	NO : <Not within 120 ± 20 Ω> Go to Step 5.

STEP 5. Resistance measurement at engine-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the engine-ECU, and measure at the equipment side.

(2)Resistance between engine-ECU connector terminal Nos.101 and 102 <4G6>
OK: 120 ± 20 Ω

(3)Resistance between engine-ECU connector terminal Nos.108 and 109 <4D5, 4N1>
OK: 120 ± 20 Ω

Q. Is the check result normal?

	<Within 120 ± 20 Ω> Check intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN2) and the engine-ECU connector.

	<Not within 120 ± 20 Ω> Check the engine-ECU connector, and repair if necessary. If the engine-ECU connector is in good condition, replace the engine-ECU (Refer to GROUP 13A - Engine-ECU <4G6>, GROUP 13B - Engine-ECU <4D5> or GROUP 13C - Engine-ECU <4N1>).

STEP 6. Resistance measurement at joint connector (CAN2).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN2), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN2) terminal Nos.8 and 19
OK: 1 kΩ or more

Q. Is the check result normal?

	YES <Vehicles with ABS or ASTC> : <1 kΩ or more> Go to Step 8.

	YES <Vehicles without ABS and ASTC> : <1 kΩ or more> Go to Step 10.

	<Less than 1 kΩ> Go to Step 7.

STEP 7. Resistance measurement at KOS&OSS-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the KOS&OSS-ECU, and measure at the equipment side.

(2)Resistance between KOS&OSS-ECU connector terminal Nos.35 and 51
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) and the KOS&OSS-ECU connector.

	<Less than 1 kΩ> Check the KOS&OSS-ECU connector, and repair if necessary. If the KOS&OSS-ECU connector is in good condition, replace the KOS&OSS-ECU (Refer to GROUP 42B - KOS&OSS-ECU).

STEP 8. Resistance measurement at joint connector (CAN2).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN2), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN2) terminal Nos.5 and 16
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Go to Step 10.

	<Less than 1 kΩ> Go to Step 9.

STEP 9. Resistance measurement at ABS-ECU or ASTC-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the ABS-ECU or ASTC-ECU, and measure at the equipment side.

(2)Resistance between ABS-ECU or ASTC-ECU connector terminal Nos.16 and 4
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Check intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN2) and the ABS-ECU or ASTC-ECU connector.

	<Less than 1 kΩ> Check the ABS-ECU or ASTC-ECU connector, and repair if necessary. If the ABS-ECU or ASTC-ECU connector is in good condition, replace the ABS-ECU (Refer to GROUP 35B - Hydraulic Unit) or ASTC-ECU (Refer to GROUP 35C - Hydraulic Unit).

STEP 10. Resistance measurement at joint connector (CAN2).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Disconnect joint connector (CAN2), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN2) terminal Nos.7 and 18
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) and joint connector (CAN1).

	<Less than 1 kΩ> Go to Step 11.

STEP 11. Resistance measurement at SRS-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the SRS-ECU, and measure at the equipment side.

(2)Resistance between SRS-ECU connector terminal Nos.33 and 34
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) and the SRS-ECU connector.

	<Less than 1 kΩ> Check the SRS-ECU connector, and repair if necessary. If the SRS-ECU connector is in good condition, replace the SRS-ECU (Refer to GROUP 52B - SRS-ECU).

STEP 12. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.11 and 22
OK: 120 ± 20 Ω

Q. Is the check result normal?

	YES <Vehicles with automatic A/C> : <Within 120 ± 20 Ω> Go to Step 14.

	YES <Vehicles without automatic A/C (A/T)> : <Within 120 ± 20 Ω> Go to Step 16.

	YES <Vehicles without automatic A/C (4WD-6M/T)> : <Within 120 ± 20 Ω> Go to Step 18.

	YES <Vehicles without automatic A/C (2WD-M/T, 4WD-5M/T)> : <Within 120 ± 20 Ω> Go to Step 20.

	NO : <Not within 120 ± 20 Ω> Go to Step 13.

STEP 13. Resistance measurement at ETACS-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the ETACS-ECU, and measure at the equipment side.

(2)Resistance at ETACS-ECU connector terminal Nos.56 and 65
OK: 120 ± 20 Ω

Q. Is the check result normal?

	<Within 120 ± 20 Ω> Repair the wiring harness between joint connector (CAN1) and the ETACS-ECU connector.

	<Not within 120 ± 20 Ω> Check the ETACS-ECU connector, and repair if necessary. If the ETACS-ECU connector is in good condition, replace the ETACS-ECU (Refer to GROUP 54A - ETACS, ETACS-ECU).

STEP 14. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.5 and 16
OK: 1 kΩ or more

Q. Is the check result normal?

	YES <A/T> : <1 kΩ or more> Go to Step 16.

	YES <4WD-6M/T> : <1 kΩ or more> Go to Step 18.

	YES <2WD-M/T, 4WD-5M/T> : <1 kΩ or more> Go to Step 20.

	<Less than 1 kΩ> Go to Step 15.

STEP 15. Resistance measurement at A/C-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the A/C-ECU, and measure at the equipment side.

(2)Resistance at A/C-ECU connector terminal Nos.1 and 2
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the A/C-ECU connector.

	<Less than 1 kΩ> Check the A/C-ECU connector, and repair if necessary. If the A/C-ECU connector is in good condition, replace the A/C-ECU (Refer to GROUP 55B - Heater Control Unit).

STEP 16. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.1 and 12
OK: 1 kΩ or more

Q. Is the check result normal?

	YES <4WD> : <1 kΩ or more> Go to Step 18.

	YES <2WD> : <1 kΩ or more> Go to Step 20.

	<Less than 1 kΩ> Go to Step 17.

STEP 17. Resistance measurement at A/T-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the A/T-ECU, and measure at the equipment side.

(2)Resistance at A/T-ECU connector terminal Nos.24 and 16
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Check intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN1) and the A/T-ECU connector.

	<Less than 1 kΩ> Check the A/T-ECU connector, and repair if necessary. If the A/T-ECU connector is in good condition, replace the A/T-ECU (Refer to GROUP 23A - A/T-ECU).

STEP 18. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.4 and 15
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Go to Step 20.

	<Less than 1 kΩ> Go to Step 19.

STEP 19. Resistance measurement at transfer-ECU connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the transfer-ECU, and measure at the equipment side.

(2)Resistance at transfer-ECU connector terminal Nos.56 and 55
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the transfer-ECU connector.

	<Less than 1 kΩ> Check the transfer-ECU connector, and repair if necessary. If the transfer-ECU connector is in good condition, replace the transfer-ECU (Refer to GROUP 22A - Transfer-ECU <M/T> or GROUP 23A - Transfer-ECU <A/T>).

STEP 20. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.2 and 13
OK: 1 kΩ or more

Q. Is the check result normal?

	YES <Vehicles with ASTC> : <1 kΩ or more> Go to Step 22.

	YES <Vehicles without ASTC> : <1 kΩ or more> Go to Step 24.

	<Less than 1 kΩ> Go to Step 21.

STEP 21. Resistance measurement at combination meter connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the combination meter, and measure at the equipment side.

(2)Resistance at combination meter connector terminal Nos.14 and 15
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the combination meter connector.

	<Less than 1 kΩ> Check the combination meter connector, and repair if necessary. If the combination meter connector is in good condition, replace the combination meter (Refer to GROUP 54A - Combination meter).

STEP 22. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.6 and 17
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Go to Step 24.

	<Less than 1 kΩ> Go to Step 23.

STEP 23. Resistance measurement at steering wheel sensor connector.

caution

A digital multimeter should be used. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Remove the steering wheel sensor, and measure at the equipment side.

(2)Resistance at steering wheel sensor connector terminal Nos.3 and 4
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> Repair the wiring harness between joint connector (CAN1) and the steering wheel sensor connector.

	<Less than 1 kΩ> Check the steering wheel sensor connector, and repair if necessary. If the steering wheel sensor connector is in good condition, replace the steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor).

STEP 24. Resistance measurement at joint connector (CAN1).

caution

A digital multimeter should be used. For details refer to service precautions.
The test wiring harness should be used. For details refer to service precautions.
When measuring the resistance, disconnect the negative battery terminal. For details refer to service precautions.
Strictly observe the specified wiring harness repair procedure. For details refer to service precautions.

(1)Disconnect joint connector (CAN1), and measure at the wiring harness side.

(2)Turn the ignition switch to the "LOCK" (OFF) position.

(3)Ensure that the negative battery terminal is disconnected.

(4)Resistance between joint connector (CAN1) terminal Nos.10 and 21
OK: 1 kΩ or more

Q. Is the check result normal?

	<1 kΩ or more> The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).

	<Less than 1 kΩ> Check the diagnosis connector, and repair if necessary. If the diagnosis connector is in good condition, repair the wiring harness between joint connector (CAN1) and the diagnosis connector.