INSPECTION PROCEDURE E-4: Keyless Entry System: Encrypted code cannot be registered: Diagnosis

Required Special Tools: 

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

1. STEP 1. Check the trouble symptom. 

   Q: Is the encrypted code register mode set? 

   1. YES :  Go to step  4 .
   2. 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 signals from the following switches:

   • Key reminder switch
   • Hazard warning light 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.
      Fig 1: Connecting Scan Tool MB991502 To Data Link Connector

      Courtesy of DAIMLERCHRYSLER CORP.

   Q: Does the tone alarm of scan tool MB991502 sound when the input signal enters? 

   1. YES :  Replace the ETACS-ECU. Check that the transmitter can be registered.
   2. NO : 
      • Scan tool MB991502 does not sound when the ignition key is removed from the ignition key cylinder: Refer to INSPECTION PROCEDURE O-3: THE KEY REMINDER SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  .
      • Scan tool MB991502 does not sound when the hazard warning light switch is turned from "OFF" to "ON": Refer to INSPECTION PROCEDURE O-4: THE HAZARD WARNING LIGHT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  .
3. STEP 3. Check the input signal (by using a voltmeter). 

   Check the input signals from the following switches:

   • Key reminder switch
   • Hazard warning light 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.
      Fig 2: Checking Input Signal (Using A Voltmeter)

      Courtesy of DAIMLERCHRYSLER CORP.

   Q: Does the voltmeter indicator deflect? 

   1. YES :  Replace the ETACS-ECU. Check that the transmitter can be registered.
   2. NO : 
      • The voltmeter needle does not fluctuate when the ignition key is removed from the ignition key cylinder: Refer to INSPECTION PROCEDURE O-3: THE KEY REMINDER SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  .
      • The voltmeter needle does not fluctuate when the hazard warning light switch is turned from "OFF" to "ON": Refer to INSPECTION PROCEDURE O-4: THE HAZARD WARNING LIGHT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU  .
4. STEP 4. Check the transmitter. 

   Q: Can the encrypted code be registered after the transmitter battery has been renewed? 

   1. YES :  No action is necessary and testing is complete.
   2. NO :  Replace the transmitter. If the transmitter can not be registered even if the transmitter has been replaced, replace the ETACS-ECU. Check that the transmitter can be registered.