Inspection Procedure 7: DC/DC Converter Power Supply System Check <Vehicles with AS&G system>

caution

Even if diagnosis code No. B1351, B1352, B1353, B1355, or B1356 is output to the AS&G-ECU, do not assume that this means a DC/DC converter or AS&G-ECU malfunction. Always check the DC/DC converter power supply circuit.

PROBABLE CAUSES

Malfunction of battery
Damaged wiring harness and connectors
Malfunction of DC/DC converter

DIAGNOSIS PROCEDURE

STEP 1. Battery test

Check the battery state.

Q. Is the check result normal?

	Go to Step 2.

	Replace the battery.

STEP 2. Check the fuse.

Check the state of fuse No.12 (in the ETACS-ECU).

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 3.

STEP 3. Recheck the fuse.

(1)Replace fuse No.12 (in the ETACS-ECU).

(2)Turn the ignition switch to the "ON" position, wait at least 1 minute, and then switch it "OFF".

(3)Check fuse No.12 (in the ETACS-ECU).

Q. Is the check result normal?

	The inspection is complete.

	Repair the power supply line (ignition switch side) between the DC/DC converter connector and the ETACS-ECU connector. Then, replace the fuse.

STEP 4. Perform voltage measurement at DC/DC converter connector (power supply terminal [ignition switch side]).

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

(2)Measure the voltage between the DC/DC converter connector (power supply terminal [ignition switch side]) and body earth.

(3)Turn the ignition switch to the "ON" position.
OK: System voltage

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 5.

STEP 5. Check for open circuit or short to earth in power supply line (ignition switch side) between the DC/DC converter connector and ETACS-ECU connector.

Q. Is the check result normal?

	Intermittent malfunction.

	Repair the connector(s) or wiring harness.

STEP 6. Perform resistance measurement at the DC/DC converter connector (earth terminal).

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

(2)Measure the resistance between the DC/DC converter connector (earth terminal) and body earth.
OK: Continuity exist (2 Ω or less).

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 7.

STEP 7. Check for open circuit in earth line between the DC/DC converter connector and body earth.

Q. Is the check result normal?

	Intermittent malfunction.

	Repair the connector(s) or wiring harness.

STEP 8. Perform voltage measurement at DC/DC converter connector (power supply terminal [battery side]).

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

(2)Measure the voltage between the DC/DC converter connector (power supply terminal [battery side]) and body earth.
OK: System voltage

Q. Is the check result normal?

	Go to Step 10.

	Go to Step 9.

STEP 9. Check for open circuit or short to earth in power supply line (battery side) between the DC/DC converter connector and the fusible link No.36.

Q. Is the check result normal?

	Intermittent malfunction.

	Repair the connector(s) or wiring harness.

STEP 10. Recheck the trouble symptom.

Q. Does the malfunction take place again?

	Replace the DC/DC converter.

	The inspection is complete.