Inspection Procedure 12

The content of this article reflects the changes identified in TSB-10-55-002.

INSPECTION PROCEDURE 12: The A/C Indicator Flashes.















TECHNICAL DESCRIPTION (COMMENT)
If the A/C indicator flashes, inadequate refrigerant quality, the ambient air temperature sensor circuit or the A/C pressure sensor circuit is suspected.

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: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)

- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

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.

Is the check result satisfactory?
Yes: Go to Step 2.
No: Refer to DIAGNOSTIC TROUBLE CODE CHART

STEP 2. Using scan tool MB991958, check data list.





1. CAUTION: To prevent damage to scan tool MB991958, always turn the ingnition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool M991958.
Connect scan tool MB991958 to the data linke connector.
2. Assemble a manifold gauge onto the high pressure service valve.
3. Turn ON the engine and then turn ON the A/C switch.
4. Set scan tool MB991958 to the data reading mode.
- Item 04: A/C pressure sensor.
- Check that the refrigerant pressure matches the displayed value on the scan tool.
5. Turn the ignition switch to the "LOCK" (OFF) position

Q. Is the sensor within the specified range?
Yes: Go to Step 7.
No: Go to Step 3.

STEP 3. Check A/C pressure sensor connector A-34 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is A/C pressure sensor connector A-34 in good condition?
Yes: Go to Step 4.
No: Repair or replace the connector. Check that the A/C works normally.

STEP 4. Check the A/C pressure sensor.












1. Assemble a gauge maniforld on the high pressure service valve.
2. Disconnect the A/C pressure sensor connector and connect special tool test harness MB991658 as shown in the illustration.
3. Turn ON the engine and then turn ON the A/C switch.
4. At this time, check to see that the voltage of A/C pressure sensor terminal No. 2 reflects the specifications of the figure.
NOTE: The allowance shall be defined as ±5%.

Is the A/C pressure sensor in good condition?
Yes: Go to Step 5.
No: Replace the A/C pressure sensor. Check that the A/C works normally.

STEP 5. Check A/C-ECU C-14 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Are A/C-ECU C-14 in good condition?
Yes: Go to Step 6.
No: Repair or replace the connector. Check that the A/C works normally.

STEP 6. Check the wiring harness between A/C-ECU connector C-14 (terminals 4, 1 and 3) and A/C pressure sensor connector A-34 (terminals 2, 1 and 3).












NOTE: Also check intermediate connector C-24 for loose, corroded or damaged terminals, or terminals pushed bakc in the connector. If intermediate connector C-24 is damaged, repair or replace the connector.
- Check the A/C-ECU signal line for open and short circuit.

Q. Is the wiring harness between A/C-ECU connector C-14 (terminals 4, 1 and 3) and A/C pressure sensor connector A-34 (terminals 2, 1 and 3) in good condition?
Yes: Repair the A/C-ECU. Check that the A/C works normally.
No: Repair the wiring harness. Check that the A/C works normally.

STEP 7. Check the refrigerant level.

Use the refrigerant recover station to remove all of the refrigerant, and then calcuate 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. Check that the A/C works normally.