INSPECTION PROCEDURE J-1: Headlight, Taillight: Taillights do not illuminate.: Diagnosis

Required Special Tools: 

• MB991223: Test Harness Set
• MB991502: Scan Tool (MUT-II)
• MB991529: Diagnostic Trouble Code Check Harness

1. STEP 1. Check the DTC. 

   Q: Does DTC set when the ignition switch is turned to the "LOCK" (OFF) position? 

   YES  : Carry out the troubleshooting by referring to the Diagnostic Trouble Code Chart. Refer to DIAGNOSTIC TROUBLE CODE CHART  .

   NO:  Go to Step 2 < when using scan tool MB991502 > or 3 < when using a voltmeter >.

2. STEP 2. Check the input signal (by using scan tool MB991502). 

   Check the input signal from the taillight 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  : Go to  Step 4.

   NO:  Scan tool MB991502 does not sound when the lighting switch is turned from "OFF" to "TAIL": Refer to INSPECTION PROCEDURE O-14 "THE TAILLIGHT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  ."

   Fig 1: Connecting Scan Tool MB991502 To Data Link Connector

   Courtesy of DAIMLERCHRYSLER CORPORATION
3. STEP 3. Check the input signal (by using a voltmeter). 

   Check the input signal from the taillight 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  : Go to Step 4.

   NO:  The voltmeter needle does not fluctuate when the lighting switch is turned from "OFF" to "TAIL": Refer to INSPECTION PROCEDURE O-14 "THE TAILLIGHT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  ."

   Fig 2: Connecting Voltmeter Between Ground Terminal 4 And 5

   Courtesy of DAIMLERCHRYSLER CORPORATION
4. STEP 4. Check the power supply circuit to the front-ECU. Test at front-ECU connector A-10X. 
   1. Disconnect front-ECU connector A-10X and measure the voltage available at the relay box side of the connector.
      Fig 3: Identifying Front-ECU Connector A-10X

      Courtesy of DAIMLERCHRYSLER CORPORATION
   2. Measure the voltage between terminal 5 and ground.
      • The voltage should equal approximately 12 volts (battery positive voltage).

   Q: Is the measured voltage approximately 12 volts (battery positive voltage)? 

   YES  : Replace the front-ECU. Check that the tail lights illuminate normally.

   NO:  Go to Go to Step 5.

   Fig 4: Measuring Voltage Between Terminal 5 And Ground

   Courtesy of DAIMLERCHRYSLER CORPORATION
5. STEP 5. Check the front-ECU connector A-10X for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Is front-ECU connector A-10X in good condition? 

   YES  : Go to Step 6.

   NO:  Repair or replace the damaged component(s). Refer to , HARNESS CONNECTOR INSPECTION . The taillights should illuminate normally.

   Fig 5: Identifying Front-ECU Connector A-10X

   Courtesy of DAIMLERCHRYSLER CORPORATION
6. STEP 6. Check the wiring harness between front-ECU connector A-10X (terminal 5) and battery. 

   Q: Is the wiring harness between front-ECU connector A-10X (terminal 5) and battery in good condition? 

   YES  : No action is necessary and testing is complete.

   NO:  The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The taillights should illuminate normally.

   Fig 6: Identifying Front-ECU Connector A-10X

   Courtesy of DAIMLERCHRYSLER CORPORATION