DTC U0164: A/C/Heater control unit CAN timeout: Diagnosis

Required Special Tools:

MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958. Refer to "HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) ."
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.
  Q: Is the CAN bus line found to be normal?
  1. YES: Go to Step 2.
  2. NO: Repair the CAN bus line (Refer to DIAGNOSIS ).
    
    Fig 1: Connecting Special Tool MB991910 To Data Link Connector
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 2. Using scan tool MB991958, read the A/C/Heater control unit diagnostic trouble code.
Check if DTC is set to the A/C/Heater control unit.

Q: Is the DTC set?
1. YES: Troubleshoot the A/C/Heater control unit (Refer to MANUAL A/C DIAGNOSIS or AUTO A/C DIAGNOSIS ).
2. NO: Go to Step 3.
STEP 3. Using scan tool MB991958, read the ETACS diagnostic trouble code.
Check if the DTC U0164 is set to the ETACS-ECU.

Q: Is the DTC set?
1. YES: Go to Step 4.
2. NO: Go to Step 5.
STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is set to the combination meter.
1. Erase the DTC.
2. Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
3. Check if DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
  Q: Is the DTC set?
  1. YES: Replace the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C>.
  2. NO: The trouble can be an intermittent malfunction such as a poor connection or open circuit in the CAN bus lines between the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C> and the combination meter (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is set to the combination meter.
1. Erase the DTC.
2. Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
3. Check if DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
  Q: Is the DTC set?
  1. YES: Replace the combination meter.
  2. NO: The trouble can be an intermittent malfunction such as a poor connection or open circuit in the CAN bus lines between the A/C-ECU <vehicles with A/C> or heater control unit <vehicles without A/C> and the combination meter (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).