Inspection Procedure 1: Trouble in HUD power supply system [Communication with the scan tool (M.U.T.-IIISE) is not possible.]: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB992006: Extra Fine Probe

1. STEP 1. Resistance measurement at HUD connector (GND terminal). 
   1. Disconnect the connector, and measure at the wiring harness side.
   2. Measure the resistance between the HUD connector (GND terminal) and body ground.

      OK: The resistance should be 2 ohms or less 

      Q: Is the check result normal? 

      YES:  Go to Step  2.

      NO:  Correct the ground circuit between the HUD connector and the body ground (ground terminal).

2. STEP 2. Voltage measurement at HUD connector (+B terminal). 
   1. Disconnect the connector, and measure at the wiring harness side.
   2. Check the voltage between the HUD connector (+B terminal) and body ground.

      OK: The voltage should measure approximately 12 volts (battery positive voltage) 

   Q: Is the check result normal? 

   YES:  Go to Step  3.

   NO:  Correct the power supply circuit between the HUD connector and the power supply (+ B terminal).

3. STEP 3. Voltage measurement at HUD connector (IG1 terminal). 
   1. Disconnect the connector, and measure at the wiring harness side.
   2. Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
   3. Check the voltage between the HUD connector (IG terminal) and body ground.

      OK: The voltage should measure approximately 12 volts (battery positive voltage) 

      Q: Is the check result normal? 

      YES:  Go to Step  4.

      NO:  Correct the power supply circuit between the HUD connector and the power supply (IG1 terminal).

4. STEP 4. Retest the system 

   Check whether the HUD can communicate with scan tool (M.U.T.-IIISE).

   Q: Is the check result normal? 

   YES:  The trouble can be an intermittent malfunction (Refer to How to use Troubleshooting/inspection Service Points - HOW TO COPE WITH INTERMITTENT MALFUNCTION ).

   NO:  Replace the HUD.