Code No. P1021: Oil Control Valve Circuit <4A9>

OPERATION

Power is supplied to the oil control valve (terminal No. 2) from the engine control relay (terminal No. 4).
The engine-ECU or engine-A-M/T-ECU (terminal No. 52) makes the power transistor in the unit be in "ON" position, and that makes currents go on the oil control valve (terminal No. 1).

FUNCTION

The oil control valve switches the cams to operate the MIVEC system in the low-speed or high-speed mode in accordance with the signals from the engine-ECU or engine-A-M/T-ECU.

TROUBLE JUDGMENT

Check Conditions

Ignition switch is "ON" position
Battery positive voltage is higher than 10 V.
MIVEC operating in the low-speed mode.

Judgment Criterion

The engine-ECU or engine-A-M/T-ECU terminal voltage of oil control valve circuit is less than 4 V for 2 seconds.

PROBABLE CAUSES

Failed oil control valve
Open or shorted oil control valve circuit, harness damage, or connector damage
Failed engine-ECU or engine-A-M/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-128 oil control valve connector

Q. Is the check result normal?

Go to Step 2 .

Repair or replace the connector.

STEP 2: Perform resistance measurement at A-128 oil control valve connector.

Disconnect connector, and measure at control valve side.
Resistance between terminal No. 1 and No. 2.

OK: 6.9 - 7.9 Ω (at 20°C)

Q. Is the check result normal?

Go to Step 3 .

Replace the oil control valve.

STEP 3. Perform voltage measurement at A-128 oil control valve connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 2 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 5 .

Go to Step 4 .

STEP 4. Connector check: B-206 engine control relay connector

Q. Is the check result normal?

Check power supply line for open/short circuit.

Repair or replace the connector.

STEP 5. Perform voltage measurement at A-08 engine-ECU connector or engine-A-M/T-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 52 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 7 .

Go to Step 6 .

STEP 6. Connector check: A-08 engine-ECU connector or engine-A-M/T-ECU connector

Q. Is the check result normal?

Check earthing line for open/short circuit.

Repair or replace the connector.

STEP 7. Connector check: A-08 engine-ECU connector or engine-A-M/T-ECU connector

Q. Is the check result normal?

Go to Step 8 .

Repair or replace the connector.

STEP 8. Check harness between A-128 (terminal No. 1) oil control valve connector and A-08 (terminal No. 52) engine-ECU connector or engine-A-M/T-ECU connector.

Check earthing line for damage.

Q. Is the check result normal?

Go to Step 9 .

Repair the damaged harness wire.

STEP 9. Check harness between A-128 (terminal No. 2) oil control valve connector and B-206 (terminal No. 4) engine control relay connector.

note

Before checking harness, check intermediate connectors A-13 and B-212, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 10 .

Repair the damaged harness wire.

STEP 10. M.U.T.-III diagnosis code.

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace the engine-ECU or engine-A-M/T-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).