Code No. P1121: Throttle Valve Control Servo Power System

OPERATION

Battery voltage is applied to the throttle valve control servo relay terminal (terminal No. 4).
Battery voltage is applied to the throttle valve control servo relay terminal (terminal No. 3) from the engine control relay (terminal No. 1).
Engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 15) applies current to the throttle valve control servo relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
When the throttle valve control servo relay turns ON, battery voltage is supplied by the throttle valve control servo relay (terminal No. 1) to the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 132).

FUNCTION

When the ignition switch ON signal is input into the engine-ECU <M/T> or engine-A/T-ECU <A/T>, the engine-ECU <M/T> or engine-A/T-ECU <A/T> turns ON the throttle valve control servo.

TROUBLE JUDGMENT

Check Condition

Ignition switch is in ON position.

Judgement Criterion

The voltage to detect a short circuit to the earth is 4.0 V or less.

PROBABLE CAUSE

Failed throttle valve control servo relay
Open/short circuit in throttle valve control servo circuit or loose connector contact
Failed engine-ECU <M/T>
Failed engine-A/T-ECU <A/T>

DIAGNOSIS

STEP 1. Connector check: B-12X throttle valve control servo relay connector

Q. Is the check result normal?

Go to Step 2 .

Repair or replace.

STEP 2. Check throttle valve control servo relay itself.

Check throttle valve control servo relay itself (Refer to ).

Q. Is the check result normal?

	Go to Step 3 .

	Replace throttle valve control servo relay.

STEP 3. Perform voltage measurement at B-12X throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Voltage between terminal No. 4 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 4 .

Check power supply line for open/short circuit.

STEP 4. Perform voltage measurement at B-12X throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Ignition switch: ON
Voltage between terminal No. 3 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 6 .

Go to Step 5 .

STEP 5. Connector check: B-15X engine control relay connector

Q. Is the check result normal?

Check power supply line for open/short circuit.

Repair or replace.

STEP 6. Connector check: C-110 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Repair or replace.

STEP 7. Perform voltage measurement at C-110 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 15 and earth.

OK: System voltage

Q. Is the check result normal?

Check earthing line for open/short circuit.

STEP 8. Connector check: C-114 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Repair or replace.

STEP 9. Perform voltage measurement at C-114 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 132 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 12 .

Go to Step 10 .

STEP 10. Check harness between B-12X (terminal No. 1) throttle valve control servo relay connector and C-114 (terminal No. 132) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Check output line for open/short circuit.

Q. Is the check result normal?

Go to Step 11 .

Repair.

STEP 11. Check harness between B-15X (terminal No. 1) engine control relay connector and B-12X (terminal No. 3) throttle valve control servo relay connector.

Check output line for damage.

Q. Is the check result normal?

Check earthing line for damage.

Repair.

STEP 12. Check harness between B-12X (terminal No. 4) throttle valve control servo relay connector and battery.

Check power supply line for damage.

Q. Is the harness connector in good condition?

Go to Step 13 .

Repair.

STEP 13. Check and repair harness between B-12X (terminal No. 1) throttle valve control servo relay connector and C-114 (terminal No. 132) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Check power supply line for damage.

Q. Is the harness connector in good condition?

Go to Step 14 .

Repair.

STEP 14. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code

Q. Is the diagnosis code set?

	Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

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