Inspection Procedure 4
INSPECTION PROCEDURE 4: The Ambient Air Temperature Display Shows "COM ERROR" or " degrees C ( degrees F)" (Middle Grade Type)CAN-BUS Line And Ambient Air Temperature Sensor Circuit Part 1:
CAN-BUS Line And Ambient Air Temperature Sensor Circuit Part 2:
CIRCUIT OPERATION
The A/C-ECU receives information on ambient air temperature from the ambient air temperature sensor Then the information is sent to the multi-center display unit (middle grade type) via CAN communication
TECHNICAL DESCRIPTION (COMMENT)
If the A/C-ECU has not informed an ambient air temperature via the CAN communication for 60 seconds or more, "COM ERROR" appears on the screen If the multi-center display unit (middle grade type) can not receive correct information from the ambient air temperature sensor at all, " degrees C ( degrees F)" will be shown
TROUBLESHOOTING HINTS
- Malfunction of multi-center display unit (middle grade type)
- Malfunction of A/C-ECU
- Malfunction of Ambient air temperature sensor
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (VCI)
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness A (Vehicles with CAN communication system)
STEP 1 Using scan tool MB991958, diagnose the CAN bus line
Use scan tool MB991958 to diagnose the CAN bus lines
1. Connect scan tool MB991958 to the data link connector
2. Turn the ignition switch to "ON" position
3. Diagnose the CAN bus line
Q: Is the check result satisfactory?
YES: Go to Step 2
NO: Repair the CAN bus lines (Refer to Diagnosis in Information Bus,-Can Bus Diagnostic Chart) After diagnosing the CAN bus lines, go to Step 3
STEP 2 Using scan tool MB991958, read A/C diagnostic trouble code
Check if an A/C system DTC is set
Q: Is the DTC set?
YES: Refer to Interior Manual A/C Diagnosis - Diagnostic Trouble Code Chart
NO: Replace multi-center display unit (middle grade type) and then go to Step 3
STEP 3 Retest the system
Check if the ambient air temperature operation screen is displayed normally
Q: Is the check result satisfactory?
YES: The procedure is complete
NO: Go to Step 1