Automatic Climate Control, ACC

B1345





Mixed-air sensor LH. Short to ground
Mixed-air sensor LH. Open circuit/short to B+

Fault symptoms
Perceived temperature in cabin too high or too low compared to the set temperature.

Conditions
The following conditions apply:
- Open circuit or short to B+ on pin 19 >4.9 V.
- Short to ground on pin 19<0.1 V.
- Measured every 440 ms and 5 consecutive measurements are required to set a diagnostic trouble code.
- The diagnostic trouble code is deleted after the ignition has been switched on 20 times if the fault conditions have not been fulfilled.
- When the diagnostic trouble code is set, the control module uses the default value, which is the relative opening of the air-mixing flap in question multiplied by the coolant temperature.





Diagnostic procedure

1. Checking the diagnostic trouble code
- Contact the ACC.

Is diagnostic trouble code B2945 displayed on the diagnostics tool?
YES
- Go to diagnostic trouble code B2945.
NO
- Go to step 2.





2. Checking the sensor's ground connection
- Unplug connector: H10-5





- Connect a test lamp between B+ and pin 10 on the female connector.





- The test lamp should light.

Is the function correct?
YES
- Go to step 3.
NO
- Rectify lead in question.
- Go to step 5.





3. Checking the control module temperature input, open circuit
- Turn the ignition key to ON





- Contact the ACC.
- Read voltage: Actual Mixed-Air Temperature LH.
- Value should be 4.7-5.0 V.

Is the function correct?
YES
- Go to step 4.
NO
- Rectify lead in question.
- Go to step 5.





4. Checking the control module temperature sensor in put, connector with jumper
- Connect a jumper wire between pin 9 on the female connector and pin 10 on the connector H1O-5.
- Read voltage: Actual Mixed-Air Temperature LH.
- Value should be 0 V.

Is the function correct?
YES
- Replace: Mixed-air temperature sensor, LH.
- Go to step 5.
NO
- Rectify lead in question.
- Go to step 5.





5. Final check
- Delete diagnostic trouble codes in all systems.





- Carry out a function check.
- Evaluate the function check.
- Check that the diagnostic trouble code does not recur.

Does the diagnostic trouble code recur?
YES
- See "Before changing a control module." Before Changing a Control Module

NO
- The steps taken to rectify the fault were correct.