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DTC B1079: A/C 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.
noteWhen DTC B1079 is set, the A/C indicator of heater controller assembly (A/C-ECU) flashes.
 
 
 
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
  • The refrigerant amount is not at the specified level, or the wiring harness or connector between the heater controller assembly (A/C-ECU) and A/C pressure sensor, and the heater controller assembly (A/C-ECU) itself or A/C pressure sensor itself may have failed.
Past trouble
  • If DTC B1079 is set as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the heater controller assembly (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
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
  • Malfunction of the A/C pressure sensor.
  • Malfunction of the heater controller assembly (A/C-ECU).
 
 
 
DIAGNOSIS
Required Special Tool:
  • MB991658: Test harness set
STEP 1. Check the condenser assembly
Check that the condenser assembly is not wet.
Is the check result normal?
Go to Step 2.
Wait until the condenser is dry, and check that no diagnostic trouble code is set.
 
STEP 2. Using scan tool (M.U.T.-III), diagnose the CAN bus line
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(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.
Is the CAN bus line found to be normal?
Go to Step 3.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 3. Using scan tool (M.U.T.-III), read the heater controller assembly (A/C-ECU) DTC.
Check that the DTC related to the heater controller assembly (A/C-ECU) is not set.
Is the DTC set?
Carry out the DTC procedures. Refer to .
Go to Step 4.
 
STEP 4. Check the A/C pressure sensor
Refer to .
Is the check result normal?
Go to Step 5.
Replace the A/C pressure sensor.
 
STEP 5. Refrigerant level check
Refer to .
Is the check result normal?
Go to Step 6.
Correct the refrigerant level.
 
STEP 6. Check whether the DTC is set again.
Is the DTC set?
Refer to Inspection Procedure 11: Heater controller assembly (A/C-ECU) power supply system .
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).