INSPECTION PROCEDURE 6: The Air-Conditioner Information is not Displayed.: Diagnosis

Required Special Tools: 

• MB991223: Harness Set
• MB991502: Scan Tool (MUT-II)

1. STEP 1. Check the communication and connection of the service function (M-BUS). 
   1. Press the adjusting switch with the ignition switch at the "LOCK" (OFF) position. Then while keeping the switch on the pressed condition, turn the ignition switch to "ACC" position.
   2. When the adjusting switch is continuously pressed for more than five seconds, the reception sound (pip sound) is heard and at the same time the service function is activated to display the service mode screen.
   3. Check the communication and connection RV METER DIAGNOSIS  .

   Q: Which of the following M-BUS is indicated? 

   1. "E1" (Communication error):  Go to Step 2.
   2. "E2" (Open circuit or not connected):  Go to Step  Step 3
   3. OK:  Go to Step  Step 4
2. STEP 2. Check the RV meter and A/C-ECU circuit by backprobing. 
   1. Do not disconnect RV meter connector D-08.
   2. ignition switch "ACC" position.
   3. Measure the voltage (waveform) between terminal 9 and ground using an oscilloscope by backprobing.
      Fig 1: Measuring Voltage Between Terminal 9 & Ground

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   4. Measure the voltage (waveform) between terminal 10 and ground by backprobing.
      Fig 2: Measuring Voltage Between Terminal 10 & Ground

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   5. Measure the voltage (waveform) between terminal 19 and ground by backprobing.
   Fig 3: Measuring Voltage Between Terminal 19 & Ground

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   Q: Is the measured voltage Hi = 4 to 5 volts and Lo = 0 to 1 volt? 

   1. YES:  Replace the RV meter display.
   2. NO:  Go to Step  Step 5
3. STEP 3. Check the harness wires between RV meter connector D-08 (terminal 9 and 10 and 19) and A/C-ECU connector D-23 (terminal 16 and 17 and 6). 
   Fig 4: Checking RV Meter Connector D-08 & A/C-ECU Connector D-23

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   Q: Are harness wires between RV meter connector D-08 (terminal 9 and 10 and 19) and A/C-ECU connector D-23 (terminal 16 and 17 and 6) in good condition? 

   1. YES:  There is no action to be taken.
   2. NO:  Repair or replace them.
4. STEP 4. Check the A/C-ECU. 
   CAUTION: To Prevent to damage to scan toll MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
   1. Connect scan tool MB991502 to the data link connector.
      Fig 5: Connecting Scan Tool To Data Link Connector

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   2. Turn the ignition switch to "ON" position.
   3. Read the A/C diagnostic trouble code.

   Q: Is the A/C diagnostic trouble code set? 

   1. YES:  Carry out troubleshooting of the A/C.
   2. NO:  There is no action to be taken.
5. STEP 5. Check the A/C-ECU by backprobing. 
   1. Do not disconnect A/C-ECU connector D-23.
   2. Ignition switch "ACC" position.
   3. Measure the voltage (waveform) between terminal 6 and ground using an oscilloscope by backprobing.
      Fig 6: Measuring Voltage (Waveform) Between Terminal 6 & Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   4. Measure the voltage (waveform) between terminal 16 and ground by backprobing.
      Fig 7: Measuring Voltage (Waveform) Between Terminal 16 & Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   5. Measure the voltage (waveform) between terminal 17 and ground by backprobing.
   Fig 8: Measuring Voltage (Waveform) Between Terminal 17 & Ground

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

   Q: Is the measured voltage Hi = 4 to 5 volts and Lo = 0 to 1 volt? 

   1. YES:  Go to Step 6.
   2. NO:  Replace the A/C-ECU.
6. STEP 6. Recheck for malfunction. 

   Q: Is a malfunction eliminated? 

   1. YES:  If no malfunctions are not found in all steps, an intermittent malfunction is suspected.
   2. NO:  Replace the RV meter.