Diagnostic Item 19: Diagnose the lines from the main bus line to the engine-ECU <M/T> or engine-A/T-ECU <A/T>.


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 JUDGMENT


If the M.U.T.-III cannot receive any signal from the engine-ECU <M/T> or engine-A/T-ECU <A/T>, CAN bus line connector(s) are broken or an open circuit has occurred.

COMMENTS ON TROUBLE SYMPTOM


Connector(s), wiring harness in the CAN bus lines, the engine-ECU <M/T> or engine-A/T-ECU <A/T> may be defective.

POSSIBLE CAUSES



DIAGNOSTIC PROCEDURE

STEP 1. Connector check: A-07 joint connector (CAN1) and A-16 intermediate connector
note When checking A-07 joint connector (CAN1), disassemble and check the engine compartment relay box by referring to .




caution The strand end of the twist wire should be within 10 cm from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side is not damaged.

Q. Is the check result normal?

Go to Step 2.

Repair a defective connector or replace the joint connector (front wiring harness assembly).

STEP 2. Resistance measurement at A-07 joint connector (CAN1) and A-16 intermediate connector.
note When checking A-07 joint connector (CAN1), disassemble and check the engine compartment relay box by referring to .
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .




(1)Disconnect the joint connector (CAN1) and the intermediate connector, and measure at the wiring harness side.
(2)Ignition switch: OFF (LOCK)
(3)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.

(4)Continuity between A-07 joint connector (CAN1) terminal No.3 and A-16 intermediate connector terminal No.12
OK: 2 Ω or less

(5)Continuity between A-07 joint connector (CAN1) terminal No.6 and A-16 intermediate connector terminal No.6
OK: 2 Ω or less
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?

<All the voltages measure 2 Ω or less> Go to Step 3 .

<Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN1) and the intermediate connector.

STEP 3. Connector check: C-112 engine-ECU <M/T> or engine-A/T-ECU <A/T> connector



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

Q. Is the check result normal?

Go to Step 4.

Repair a defective connector or replace the joint connector.

STEP 4. Resistance measurement at A-16 intermediate connector and C-112 engine-ECU <M/T> or engine-A/T-ECU <A/T> connector.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .






(1)Disconnect the engine-ECU <M/T> or engine-A/T-ECU <A/T> connector and the intermediate connector, and measure at the wiring harness side.
(2)Ignition switch: OFF (LOCK)
(3)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.

(4)Continuity between A-16 intermediate connector terminal No.6 and C-112 engine-ECU <M/T> or engine-A/T-ECU <A/T> connector terminal No.61.
OK: 2 Ω or less

(5)Continuity between A-16 intermediate connector terminal No.12 and C-112 engine-ECU <M/T> or engine-A/T-ECU <A/T> connector terminal No.62.
OK: 2 Ω or less
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?

<All the resistances measure 2 Ω or less> Power supply to the engine-ECU <M/T> or engine-A/T-ECU <A/T> may be suspected. Diagnose the engine control system. Refer to <except vehicles for Hong Kong and Singapore> or <vehicles for Hong Kong and Singapore>.

<Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between the engine-ECU <M/T> or engine-A/T-ECU <A/T> connector and the intermediate connector.