Code No. P1041: Valve Lift Control Motor Abnormal Voltage Drop Of Driving Power Supply

OPERATION

Battery voltage is applied to the valve lift control motor relay connector terminal.
Engine-ECU connector terminal VLCR applies current to the valve lift control motor relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
When the valve lift control motor relay turns ON, battery voltage is supplied by the valve lift control motor relay connector terminal to the valve lift ECU connector terminal BATM.

FUNCTION

If the engine-ECU receives ignition switch ON signal through the ETACS-ECU, the ECU will turn on the valve lift control motor relay. This will allow power supply from the valve lift control motor to be delivered to the valve lift ECU.

TROUBLE JUDGMENT

Check Conditions

After 2 seconds since the ignition switch is turned ON or since the completion of engine start.
The valve lift ECU has determined that the system communicates with the engine-ECU via local CAN normally.

Judgement Criterion

The engine-ECU has received malfunction from the valve lift ECU via CAN.
Contents of malfunction which the valve lift ECU detects

Power supply voltage for activating the valve lift control motor is 8 V or less

FAIL-SAFE AND BACKUP FUNCTION

None

PROBABLE CAUSES

Failed valve lift control motor relay
Open/short circuit or harness damage in valve lift control motor relay circuit or loose connector contact.
Open circuit or harness damage in valve lift ECU earth circuit, or loose connector contact.
Failed valve lift ECU
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check valve lift control motor relay itself.

Valve lift control motor relay connector check.
Check valve lift control motor relay itself (Refer to ).

Q. Is the check result normal?

	Go to Step 2.

	Repair or replace the connector, or replace the valve lift control motor relay.

STEP 2. Perform resistance measurement at valve lift ECU connector.

Disconnect connector, and measure at harness side.
Resistance between terminal GND and body earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or check and repair harness between valve lift ECU connector terminal GND and body earth. Check power supply line for open/short circuit.

STEP 3. Perform voltage measurement at valve lift control motor relay connector.

Remove relay, and measure at relay box side.
Voltage between terminal power supply line and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 4.

	Repair or replace the connector, or check and repair harness between valve lift control motor relay connector terminal and battery. Check power supply line for open/short circuit.

STEP 4. Perform voltage measurement at engine-ECU connector.

Disconnect connector, and measure at harness side.
Voltage between terminal VLCR and body earth

OK: System voltage

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or check and repair harness between valve lift control motor relay connector terminal and engine-ECU connector terminal VLCR. Check signal line for open/short circuit.

STEP 5. Perform voltage measurement at valve lift ECU connector.

Disconnect connector, and measure at harness side.
Short-circuit engine-ECU connector terminal VLCR to the body earth.
Voltage between terminal BATM and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 6.

STEP 6. Check harness between valve lift control motor relay connector terminal and valve lift ECU connector terminal BATM.

Check output line for open/short circuit.

Q. Is the check result normal?

	Go to Step 7.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 7. Check harness between valve lift control motor relay connector terminal and Engine-ECU connector terminal VLCR.

Check signal line for damage.

Q. Is the check result normal?

	Repair or replace the connector, or check and repair harness between valve lift control motor relay connector terminal and battery. Check power supply line for damage.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 8. Check harness between valve lift control motor relay connector terminal and valve lift ECU connector terminal BATM.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 9.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 9. Check harness between valve lift control motor relay connector terminal and battery

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 10.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 10. Perform voltage measurement at engine-ECU connector

Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
Voltage between terminal VLCR and body earth.

OK:
System voltage [ignition switch: "LOCK" (OFF) ]
1 V or less (ignition switch: ON)

Q. Is the check result normal?

	Go to Step 12.

	Go to Step 11.

STEP 11. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace the engine-ECU.

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

STEP 12. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace the valve lift ECU.

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