Diagnosis Item 4: Diagnose shorts in the ground to CAN-C bus line

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.

FUNCTION

If a short to earth is present in the CAN-C lines, this diagnosis result will be set.

TRUBLE JUDGEMENT CONDITIONS

If diagnosis code U1120 is set, the ETACS-ECU determines that there is a failure.

TROUBLESHOOTING HINTS

Malfunction of the connector (short to earth inside connector)
Malfunction of the wiring harness (short to earth in the CAN-C main or sub bus lines)
Malfunction of the ECU (ETACS-ECU, or ECUs on CAN-C lines failed)

DIAGNOSIS PROCEDURE

STEP 1. Check the wiring harness between C-130 4WD-ECU connector and C-04 joint connector (CAN2) for short to earth (resistance measurement).

caution

Disconnect the negative battery terminal. For details refer to .
A digital multimeter should be used. For details refer to .
The test wiring harness should be used. For details refer to .

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

(2)Resistance between C-04 joint connector (CAN2) terminal No.5 and body earth
OK: 1 kΩ or more

(3)Resistance between C-04 joint connector (CAN2) terminal No.16 and body earth
OK: 1 kΩ or more

Q. Is the check result normal?

	YES <vehicles without ASC> : Go to Step 3.

	YES <vehicles with ASC> : Go to Step 2.

	NO (the check result is not normal.) : Go to Step 6.

STEP 2. Check the wiring harness between C-209 steering wheel sensor connector and C-04 joint connector (CAN2) for short to earth (resistance measurement).

caution

Disconnect the negative battery terminal. For details refer to .
A digital multimeter should be used. For details refer to .
The test wiring harness should be used. For details refer to .

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

(2)Resistance between C-04 joint connector (CAN2) terminal No.4 and body earth
OK: 1 kΩ or more

(3)Resistance between C-04 joint connector (CAN2) terminal No.15 and body earth
OK: 1 kΩ or more

Q. Is the check result normal?

	Go to Step 3.

	Go to Step 7.

STEP 3. Check the wiring harness between C-301 ETACS-ECU connector and C-04 joint connector (CAN2) for short to earth (resistance measurement).

caution

Disconnect the negative battery terminal. For details refer to .
A digital multimeter should be used. For details refer to .
The test wiring harness should be used. For details refer to .

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

(2)Resistance between C-04 joint connector (CAN2) terminal No.7 and body earth
OK: 1 kΩ or more

(3)Resistance between C-04 joint connector (CAN2) terminal No.20 and body earth
OK: 1 kΩ or more

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 8.

STEP 4. Check the wiring harness between B-06 engine-ECU connector and C-01 joint connector (CAN3) for short to earth (resistance measurement).

caution

Disconnect the negative battery terminal. For details refer to .
A digital multimeter should be used. For details refer to .
The test wiring harness should be used. For details refer to .

(1)Disconnect joint connector (CAN3), and measure at the wiring harness side.

(2)Resistance between C-01 joint connector (CAN3) terminal No.4 and body earth
OK: 1 kΩ or more

(3)Resistance between C-01 joint connector (CAN3) terminal No.15 and body earth
OK: 1 kΩ or more

Q. Is the check result normal?

	Go to Step 5.

	Go to Step 9.

STEP 5. Check the wiring harness between A-02 ABS-ECU connector <vehicles without ASC> or A-03 ASC-ECU connector <vehicles with ASC> and C-01 joint connector (CAN3) for short to earth (resistance measurement).

caution

Disconnect the negative battery terminal. For details refer to .
A digital multimeter should be used. For details refer to .
The test wiring harness should be used. For details refer to .

(1)Disconnect joint connector (CAN3), and measure at the wiring harness side.

(2)Resistance between C-01 joint connector (CAN3) terminal No.6 and body earth
OK: 1 kΩ or more

(3)Resistance between C-01 joint connector (CAN3) terminal No.19 and body earth
OK: 1 kΩ or more

Q. Is the check result normal?

	Repair the wiring harness between C-04 joint connector (CAN2) and C-01 joint connector (CAN3).

	Go to Step 10.

STEP 6. M.U.T.-III CAN bus diagnostics (checking the 4WD-ECU for internal short to earth)

caution

Strictly observe the specified wiring harness repair procedure. For details refer to

Disconnect C-130 4WD-ECU connector, and diagnose the CAN bus line.

OK: The display of the M.U.T.-III is as shown in the figure.

Q. Does M.U.T.-III screen correspond to the illustration?

Check C-35 intermediate connector, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between C-130 4WD-ECU connector and C-04 joint connector (CAN2).

Check the 4WD-ECU connector, and repair if necessary. If the 4WD-ECU connector is in good condition, replace the 4WD-ECU.

STEP 7. M.U.T.-III CAN bus diagnostics (checking the steering wheel sensor for internal short to earth)

caution

Strictly observe the specified wiring harness repair procedure. For details refer to

Disconnect C-209 steering wheel sensor connector, and diagnose the CAN bus line.

OK: The display of the M.U.T.-III is as shown in the figure.

Q. Does M.U.T.-III screen correspond to the illustration?

Repair the wiring harness between C-209 steering wheel sensor connector and C-04 joint connector (CAN2).

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.

STEP 8. M.U.T.-III CAN bus diagnostics (checking the ETACS-ECU for internal short to earth)

caution

Strictly observe the specified wiring harness repair procedure. For details refer to

Disconnect C-301 ETACS-ECU connector, and diagnose the CAN bus line.

OK: The display of the M.U.T.-III is as shown in the figure.

Q. Does M.U.T.-III screen correspond to the illustration?

Repair the wiring harness between C-301 ETACS-ECU connector and C-04 joint connector (CAN2).

Check the ETACS-ECU connector, and repair if necessary. If the ETACS-ECU connector is in good condition, ETACS-ECU.

STEP 9. M.U.T.-III CAN bus diagnostics (checking the engine-ECU for internal short to earth)

caution

Strictly observe the specified wiring harness repair procedure. For details refer to

Disconnect B-06 engine-ECU connector, and diagnose the CAN bus line.

OK: The display of the M.U.T.-III is as shown in the figure.

Q. Does M.U.T.-III screen correspond to the illustration?

Repair the wiring harness between B-06 engine-ECU connector and C-01 joint connector (CAN3).

Check the engine-ECU connector, and repair if necessary. If the engine-ECU connector is in good condition, replace the engine-ECU.

STEP 10. M.U.T.-III CAN bus diagnostics (checking the ABS-ECU <vehicles without ASC> or ASC-ECU <vehicles with ASC> for internal short to earth)

caution

Strictly observe the specified wiring harness repair procedure. For details refer to

Disconnect A-02 ABS-ECU connector <vehicles without ASC> or A-03 ASC-ECU connector <vehicles with ASC>, and diagnose the CAN bus line.

OK: The display of the M.U.T.-III is as shown in the figure.

Q. Does M.U.T.-III screen correspond to the illustration?

Repair the wiring harness between A-02 ABS-ECU connector <vehicles without ASC> or A-03 ASC-ECU connector <vehicles with ASC> and C-01 joint connector (CAN3).

Check the ABS-ECU <vehicles without ASC> or ASC-ECU <vehicles with ASC> connector, and repair if necessary. If the ABS-ECU <vehicles without ASC> or ASC-ECU <vehicles with ASC> connector is in good condition, replace the ABS-ECU <vehicles without ASC> or ASC-ECU <vehicles with ASC>.