Inspection Procedure 11

INSPECTION PROCEDURE 11: The A/C Indicator Flashes.


















TECHNICAL DESCRIPTION (COMMENT)

If the A/C indicator flashes, inadequate refrigerant quantity, 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.

Q. Is the check result satisfactory?

YES Go to Step 2.

NO Refer to DIAGNOSTIC TROUBLE CODE CHART Automatic Air Conditioning.

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





(1)
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.

Connect scan tool MB991958 to the data link 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 8.

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. Harness Connector Inspection.
Check that the A/C works normally.

STEP 4. Check the A/C pressure sensor.

(1)Assemble a gauge manifold 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%.

Q. 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-15 and C-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Are A/C-ECU C-15 and C-20 in good condition?

YES Go to Step 6.

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

STEP 6. Check the wiring harness between A/C-ECU connector C-20 (terminals 26 and 34) and A/C pressure sensor connector A-34 (terminals 2 and 1).













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

- Check the A/C-ECU signal line for open and short circuit.

Q. Is the wiring harness between A/C-ECU connector C-20 (terminals 26 and 34) and A/C pressure sensor connector A-34 (terminals 2 and 1) in good condition?

YES Go to Step 7.

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

STEP 7. Check the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3).













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

Q. Is the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3) in good condition?

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

NO Repair the wiring harness.

STEP 8. Check the refrigerant level.

Use the refrigerant recovery 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 Refrigerant Leak Repair Procedure).
Check that the A/C works normally.