Symptom Diagnostic Procedures

The content of this article and images reflects the changes identified in TSB- 10-55-003.



The A/C Indicator Flashes.








TROUBLESHOOTING HINTS
- Malfunction of the A/C pressure sensor
- Malfunction of the ambient air temperature sensor
- Malfunction of the A/C-ECU

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle 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, read the diagnostic trouble code.
Check if an A/C-ECU DTC is set.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the check result satisfactory?

YES: Go to Step 2.

NO: Refer to DIAGNOSTIC TROUBLE CODE CHART. Diagnostic Trouble Code Descriptions






STEP 2. Check A/C pressure sensor connector A-28 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is A/C pressure sensor connector A-28 in good condition?

YES: Go to Step 3.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning works normally.









STEP 3. Check the A/C pressure sensor.

(1) Assemble a gauge manifold on the highh pressure service valve.
(2) Disconnect the A/C pressure sensor connector and connect special tool MB991658 as shown in the illustration.
(3) Turn ON the engine and then turn ON the air conditioner switch.





(4) At this time check to see that the voltage of A/C pressure sensor terminal No. 2 reflecs the specifications of the figure.

NOTE: The allowance shall be defined as +/-5%.

Q: Is the A/C pressure sensor in good condition?

YES: Go to Step 4.

NO: Replace the NO pressure sensor. Check that the A/C works normally.






STEP 4. Check A/C-ECU connector C-42 for loose, corroded or damaged term~na Is or terminals pushed back in the connector.

Q: Is A/C-ECU connector C-42 in good condtion?

YES: Go to Step 5.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the A/C works normally.









STEP 5. Check the wiring harness between A/C-ECU connector C-42 (terminals 3, 1 and 4) and A/C pressure sensor connector A-28 (terminals 3, 1 and 2).

NOTE: Also check intermediate connector C-31 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-31 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-42 (terminals 3, 1 and 4) and A/C preesure sensor connector A-28 (terminals 3, 1 and 2) in good condition?

YES: Go to Step 6.

NO: Repair the wiring harness. Check that the A/C works normally.





STEP 6. Check ambient air temperature sensor connector A-25 for loose, corroded, or damaged terminals, or terminals pushed back in the connector.

Q: Is ambient air temperature sensor connector A-25 in good condition?

YES: Go to Step 7.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the A/C works normally.






STEP 7. Check the ambient air temperature sensor.

(1) Diconnect ambient air temperature sensor connector A-22.

CAUTION
The ambient air temperature sensor should be checked without removing it. If the sensor is removed it is no longer serviceable.





(2) Measure the resistance between the sensor terminals under at least two temperatures. The resistance values should meet the values shown.

NOTE: The temperature should be with in the shown range.

Q: Is the ambient air temperature sensor in good condition?

YES: Go to Step 8.

NO: Replace the ambient air temperature sensor. Check that the A/C works normally.





STEP 8. Check A/C-ECU connector C-42 for loose, corroded, or damaged terminals, or terminals pushed back In the connector.

Q: Is A/C-ECU connector C-42 in good condition?

YES: Go to Step 9.

NO: Repair or replace the connector. Rate to Harness Connector Inspection. Check that the A/C works normally.









STEP 9. Check the wiring harness between A/C-ECU connector C-42 (terminals 10 and 14) and ambient air temperature sensor connector A-22 (terminals 1 and 2).





NOTE: Also check intermediate connector C-24 and jont connector C-104 for loose, corroded, or damaged terminals, terminals pushed back in the connector. If intermediate connector C-24 or joint connector C-1O4 is damaged repair replace the connector as described in Harness Connector Inspection.

Q:Are the wiring harness between A/C-ECU connector C-42 (terminals 10 and 14) and ambient air temperature sensor connector A-22 (terminals 1 and 2) in good condition?

YES: Go to Step 10.

NO: Repair the wiring harness. Check that the A/C works normally.






STEP 10. Check the refrigerant level.

Use the refrigerant recoverv station to remove all of the refrigerant and then calculate the amount of the refrigerant and charge it.

Q: Is the refrigerant level correct?

YES: Replace the A/C-ECU. Check that the A/C works normally.

NO: Correct the refrigerant level (Refer to On-vehicle Service). Check that the A/C works normally.