B1012

DTC B1011, B1012: Ambient Air Temperature Sensor System

CAUTION: If DTC B1011 or B1012 has been set, multi-display related DTC U1130 is also set. After B1011 or B1012 has been diagnosed, don't forget to erase DTC U1130.

Ambient Temperature Sensor Circuit (Part 1):

Ambient Temperature Sensor Circuit (Part 2):

DTC SET CONDITION
- DTC B1011 is set if there is a short circuit in the ambient air temperature sensor input circuit.
- DTC B1012 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 A/C-ECU, the ambient air temperature sensor, or connector(s) or wiring between the two may be defective.

Past trouble
- If DTC B1011 or B1012 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the A/C-ECU and the ambient air temperature 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 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, diagnose the CAN bus line.

Use scan tool MB991958 to diagnose the CAN bus lines.







1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to "ON" position.
3. Diagnose the CAN bus line.

Q: Is the check result satisfactory?

YES : Go to Step 2.

NO : Repair the CAN bus lines. Then go to Step 8.

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 check result satisfactory?

YES : It can be assumed that this malfunction is intermittent.

NO : Go to Step 3.

STEP 3. Using scan tool MB991958, check data list.







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.

1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Set scan tool MB991958 to the data reading mode.
- Item 02: Ambient air temperature sensor.
- Check that the ambient temperature matches the displayed value on the scan tool.

NOTE: When this DTC is set and the system is fail-safe status, the value of service data displays 20 °C.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the sensor within the specified range?

YES : Replace the A/C-ECU. Then go to Step 8.

NO : Go to Step 4.

STEP 4. Check ambient air temperature sensor connector A-25 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is ambient air temperature sensor connector A-25 in good condition?

YES : Go to Step 5.

NO : Repair or replace the connector. Then go to Step 8.

STEP 5. Check the ambient air temperature sensor.







1. Disconnect ambient air temperature sensor connector A-25.

CAUTION: The ambient air temperature sensor should be checked without removing it. If the sensor is removed, it is no longer serviceable.







2. Measure the resistance between the sensor terminals under at least two temperatures. The resistance values should meet the values shown.

NOTE: The temperature should be within the shown range.

Q: Is the ambient air temperature sensor in good condition?

YES : Go to Step 6.

NO : Replace the ambient air temperature sensor. Then go to Step 8.

STEP 6. Check A/C-ECU connectors C-15 and C-16 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Are A/C-ECU connectors C-15 and C-16 in good condition?

YES : Go to Step 7.

NO : Repair or replace the connector. Then go to Step 8.

STEP 7. Check the wiring harness between A/C-ECU connector C-15 (terminal 20), C-16 (terminal 23) and ambient air temperature sensor connector A-25 (terminals 1 and 2).












NOTE: Also check intermediate connector C-23 and joint connector C-03 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-23 or joint connector C-03 is damaged, repair or replace the connector as described.

Q: Are the wiring harness between A/C-ECU connector C-15 (terminal 20), C-16 (terminal 23) and ambient air temperature sensor connector A-25 (terminals 1 and 2) in good condition?

YES : Replace the A/C-ECU. Then go to Step 8.

NO : Repair the wiring harness. Then go to Step 8.

STEP 8. 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 check result satisfactory?

YES : The procedure is complete.

NO : Return to Step 1.