Manual Air Conditioning [Vehicles Without A/C]
DTC B1031, B1032: Air Thermo Sensor System [Vehicles without A/C]
DTC SET CONDITION
- DTC B1031 is set if there is a short circuit in the air thermo sensor input circuit.
- DTC B1032 is set if there is a defective connector connection, or if there is an open circuit in the harness.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- The heater control unit, the air thermo sensor, or connector(s) or wiring between the two may be defective.
Past trouble
- If DTC B1031 or B1032 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the heater control unit and the air thermo 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 air thermo sensor.
- Malfunction of the heater control unit.
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) Reading and Clearing Diagnostic Trouble Codes."
(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 air thermo sensor connector C-119 and heater control unit connector C-47 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q. Are air thermo sensor connector C-119 and heater control unit connector C-47 in good condition?
YES Go to Step 4.
NO Repair or replace the connector. Harness Connector Inspection.
STEP 4. Check the wiring harness between heater control unit connector C-47 (terminals 22 and 21) and air thermo sensor connector C-119 (terminals 1 and 2).
- Check the sensor signal line and ground line for open and short circuit.
Q. Is the wiring harness between heater control unit connector C-47 (terminals 22 and 21) and air thermo sensor connector C-119 (terminals 1 and 2) in good condition?
YES Go to Step 5.
NO Repair the wiring harness.
STEP 5. Check the air thermo sensor.
Measure the resistance between connector terminals 1 and 2 under at least two different temperatures. The resistance values should generally match those in the graph.
NOTE:
The temperature at the check should not exceed the range in the graph.
Q. Is the air thermo sensor in good condition?
YES Replace the heater control unit. Then go to Step 6.
NO Replace the air thermo sensor. Then go to Step 6.
STEP 6. 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.