B1079

DTC B1079: Refrigerant Leaks


















DTC SET CONDITION

DTC B1079 will be set when the A/C pressure sensor detects the refrigerant pressure of specified level or less.

NOTE:
When DTC B1079 is set, the A/C indicator of A/C control panel flashes.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

- The refrigerant amount is not at the specified level, or the wiring harness or connector between the A/C-ECU and A/C pressure sensor, and the A/C-ECU itself or A/C pressure sensor itself may have failed.

Past trouble

- If DTC B1079 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the A/C-ECU and the A/C pressure sensor. If the connectors and wiring are normal, and obviously the ECU is the cause of the trouble, replace the ECU. If in doubt, do not replace the ECU.

TROUBLESHOOTING HINT

- Malfunction of connector.
- Malfunction of the harness.
- Malfunction of the A/C pressure sensor.
- Malfunction of the A/C-ECU.

DIAGNOSIS

Required Special Tool:

- 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

STEP 1. Using scan tool MB991958, diagnose the CAN bus line





(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. Refer to "How to connect the Scan Tool (M.U.T.-III) Scan Tool Testing and Procedures."
(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?

YES Go to Step 2.

NO Repair the CAN bus line. CAN Bus Diagnostics Chart).

STEP 2. 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 DTC set?

YES Go to Step 3.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
STEP 3. Check A/C pressure sensor connector A-53 and A/C-ECU connector C-22 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Are air A/C pressure sensor connector A-53 and A/C-ECU connector C-22 in good condition?

YES Go to Step 4.
NO Repair or replace the connector. Harness Connector Inspection.
STEP 4. Check the wiring harness between A/C-ECU connector C-22 (terminals 20, 16 and 19) and A/C pressure sensor connector A-53 (terminals 3, 2 and 1).

NOTE:
Also check intermediate connector C-130 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-130 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

- Check the sensor signal line and ground line for open and short circuit.

Q. Is the wiring harness between A/C-ECU connector C-22 (terminals 20, 16 and 19) and A/C pressure sensor connector A-53 (terminals 3, 2 and 1) in good condition?

YES Go to Step 5.
NO Repair the wiring harness.
STEP 5. Check the A/C pressure sensor operation.

(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 operating properly?

YES Go to Step 6.

NO Replace the A/C pressure sensor. Then go to Step 7.

STEP 6. 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 Go to Step 7.
NO Correct the refrigerant level (Refer to On-vehicle Service Charging [Vehicles Using R-134a Refrigerant]).
Then go to Step 7.
STEP 7. Recheck for diagnostic trouble code.

Check again if the 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 DTC set?

YES Return to Step 1.
NO The procedure is complete.