Inspection Procedure M-2
Dome Light: Dome Light Dimming Function Does Not Work NormallyTECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU dims the dome light according to the input signals from the following switches:
- Ignition switch (IG1)
- Key reminder switch
- Door switches
- Driver's door lock actuator switch
If the dome light does not be dimmed normally, the relevant input signal circuit or the ETACS-ECU may be defective.
TROUBLESHOOTING HINTS
- Malfunction of the key reminder switch
- Malfunction of the door switches.
- Malfunction of the driver's door lock actuator switch
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Check the ETACS-ECU power supply circuit. Do all of the following functions work when the ignition switch is turned to the "LOCK" (OFF) position?
- Ignition key reminder tone alarm function
- Light reminder tone alarm function
- Central door locking system
- Ignition key hole illumination light
- Hazard warning light
- Theft-alarm system
Q: Do any of the functions work?
YES: Go to Step 2
NO: Check the ETACS-ECU battery circuit. Refer to Inspection Procedure P-1.
STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the following switches:
- Ignition switch (IG1)
- Key reminder switch
- Door switches
- Driver's door lock actuator switch
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.
Q: Does the tone alarm of scan tool MB991502 sound when the Input signal enters?
YES: Replace the ETACS-ECU. The dome light dimming function should work normally.
NO: Check the relevant input signal circuit.
STEP 3. Check the input signal (by using a voltmeter). Check the input signals from the following switches:
- Ignition switch (IG1)
- Key reminder switch
- Driver's and passengers door switch
- Driver's door lock actuator switch
1. Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
2. Check that the voltmeter indicator deflects once when the input signal enters.
Q: Does the voltmeter indicator deflect?
YES: Replace the ETACS-ECU. The dome light dimming function should work normally.
NO: Check the relevant input signal circuit.