DTC 22

DTC 022: Failures Information on A/C-ECU

CAUTION: If DTC 022 is set in the multi-center display, always diagnose the CAN bus lines.

CIRCUIT OPERATION
The multi-center display unit (middle grade type) communicates with the A/C-ECU via CAN bus lines.

DTC SET CONDITION
The multi-center display unit (middle grade type) communicates with the A/C-ECU via CAN bus lines. If the A/C-ECU sends failure information, DTC 022 will be set.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble
- The A/C-ECU or the multi-center display unit (middle grade type) may be defective.

Past trouble
- Carry out diagnosis with particular emphasis on connector(s) or wiring harness between the A/C-ECU and the multi-center display unit (middle grade type). For diagnosis procedures, refer to "How to cope with past trouble" (Refer to How to Use Troubleshooting/Inspection Service Points).

TROUBLESHOOTING HINTS
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.
- Malfunction of A/C-ECU.
- Malfunction of ambient temperature sensor.
- Malfunction of multi-center display unit (middle grade type)

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991911: M.U.T.-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 Information Bus, Diagnosis-Can Bus Diagnostic Chart). On completion, go to Step 5.

STEP 2. Using scan tool MB991958, read A/C-ECU diagnostic trouble code.

Check if an A/C-ECU DTC is set.

Q: Is the DTC set?

YES: Refer to Manual A/C Diagnosis - Diagnostic Trouble Code Chart Diagnostic Trouble Code Descriptions or Auto A/C Diagnostic Trouble Code Chart Diagnostic Trouble Code Descriptions and then go to Step 3.

NO: Go to Step 4.

STEP 3. Recheck for diagnostic trouble code.

Recheck if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.

Q: Is the check result satisfactory?

YES: A poor connection, open circuit or other intermittent malfunction is present in the lines between the A/C-ECU and the multi-center display unit (middle grade type) (Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).

NO: Replace A/C-ECU and then go to step 4.

STEP 4. Recheck for diagnostic trouble code.

Recheck if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.

Q: Is the check result satisfactory?

YES: A poor connection, open circuit or other intermittent malfunction is present in the lines between the A/C-ECU and the multi-center display unit (middle grade type) (Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).

NO: Replace multi-center display unit (middle grade type) and then go to step 5.

STEP 5. Recheck for diagnostic trouble code.

Recheck if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.

Q: Is the check result satisfactory?

YES: The procedure is complete. (If no malfunctions are found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).

NO: Go to Step 1.