ENGINE (DIAGNOSTICS)(H4DOTC) > Diagnostics for Engine Starting Failure

CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM)

CAUTION:

After repairing or replacing the defective part, perform the Clear Memory Mode and Inspection Mode .

WIRING DIAGRAM:

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1.CHECK MAIN RELAY.

1) Turn the ignition switch to OFF.

2) Remove the main relay.

3) Connect the battery to main relay terminals No. 23 and No. 24.

4) Measure the resistance between main relay terminals.

Terminals

No. 21 — No. 22:

Is the resistance less than 1 Ω?

Replace the main relay.

2.CHECK GROUND CIRCUIT FOR ECM.

1) Disconnect the connectors from the ECM.

2) Measure the resistance of harness between ECM and chassis ground.

Connector & terminal

(B134) No. 5 — Chassis ground:

(B137) No. 1 — Chassis ground:

(B137) No. 2 — Chassis ground:

(B137) No. 3 — Chassis ground:

(B137) No. 7 — Chassis ground:

Is the resistance less than 5 Ω?

Repair the open circuit of the harness between the ECM and engine ground.

3.CHECK INPUT VOLTAGE OF ECM.

1) Turn the ignition switch to ON.

2) Measure the voltage between ECM and chassis ground.

Connector & terminal

(B135) No. 5 (+) — Chassis ground (−):

(B135) No. 19 (+) — Chassis ground (−):

Is the voltage 10 V or more?

Repair the open or ground short circuit of power supply circuit.

4.CHECK INPUT VOLTAGE OF MAIN RELAY.

Measure the voltage between main relay connector and chassis ground.

Connector & terminal

(B220) No. 21 (+) — Chassis ground (−):

(B220) No. 23 (+) — Chassis ground (−):

Is the voltage 10 V or more?

Repair the open or ground short circuit of power supply circuit.

5.CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR.

1) Turn the ignition switch to OFF.

2) Measure the resistance of harness between ECM and main relay connector.

Connector & terminal

(B136) No. 23 — (B220) No. 40:

Is the resistance less than 1 Ω?

Repair the open circuit of harness between ECM and main relay connector.

6.CHECK INPUT VOLTAGE OF ECM.

1) Turn the ignition switch to OFF.

2) Connect the connector to ECM.

3) Turn the ignition switch to ON.

4) Measure the voltage between ECM and chassis ground.

Connector & terminal

(B134) No. 7 (+) — Chassis ground (−):

(B135) No. 2 (+) — Chassis ground (−):

Is the voltage 10 V or more?

Check ignition control system.

Repair the harness and connector.

NOTE:

In this case, repair the following item:

• Open circuit in harness between ECM and main relay connector

• Poor contact of main relay connector