Inspection Procedure 8

Inspection Procedure 8: Daytime running light function does not work normally.

CAUTION: Whenever the ECU is replaced, ensure that the input and output signal circuits are normal.

Daylight Running Light Circuit:

TECHNICAL DESCRIPTION (COMMENT)
If the daytime running light function does not work, connector(s), wiring harness in the CAN bus lines, the engine control module, the combination meter, the ETACS-ECU or the input signal circuit may be defective.

TROUBLESHOOTING HINTS
- Trouble in input signal system
- Malfunction of the ETACS-ECU
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Verify the headlight (low-beam) operation.

Check to see that the headlight (low-beam) lights up properly when operating the dimmer switch while the headlight switch is ON.

Q: Do the headlights (low-beam) illuminate normally?

YES : Go to Step 2.

NO : Refer to Inspection Procedure 1 "Headlights (low-beam) do not illuminate normally." Inspection Procedure 1

STEP 2. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.




1. Connect scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III)." Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES : Go to Step 3.

NO : Repair the CAN bus line (Refer to Controller area network Diagnosis).

STEP 3. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.

Check whether ETACS-ECU DTCs are set.

1. Turn the ignition switch to the "ON" position.
2. Check for ETACS-ECU DTCs.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Diagnose the ETACS-ECU. Refer to ETACS, Diagnosis. Diagnostic Trouble Code Descriptions

NO : Go to Step 4.

STEP 4. Using scan tool MB991958, read the MFI system diagnostic trouble code.

Check whether engine control module DTCs are set or not.

1. Turn the ignition switch to the "ON" position.
2. Check for engine control module DTCs.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Diagnose the MFI system. Refer to Diagnosis.

NO : Go to Step 5.

STEP 5. Check the parking brake switch.

Check the input signals from the parking brake switch.

1. Turn the ignition switch to the "ON" position.
2. Check that the brake warning light on the combination meter goes off when the parking brake lever is released.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Does the brake warning light go off?

YES : Replace the ETACS-ECU. Verify that the daytime running light function does not work normally.

NO : Refer to Parking brake Diagnosis, Inspection Procedure 3. Verify that the daytime running light function does not work normally.