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B1406, B1407, B1408

Symptom: TCS OFF lamp on, TCS system inoperative and possibly trouble codes in MOTRONIC.

B1406, B1407, B1408

Position sensor, main throttle butterfly, faulty, no continuity/short circuit


Fault symptom

TCS OFF lamp on, TCS system inoperative and possibly trouble codes in MOTRONIC.

Condition

For trouble code B1406: Main throttle butterfly position signal from pin 54 of the MOTRONIC control module to pin 11 of the TCS control module incorrect.

For trouble code B1407: Main throttle butterfly position signal from pin 54 of the MOTRONIC control module to pin 11 of the TCS control module shorted to ground.

For trouble code B1408: Main throttle butterfly position signal from pin 54 of the MOTRONIC control module to pin 11 of the TCS control module shorted to battery + or no continuity.

Diagnostic procedure


1. If the CHECK ENGINE lamp (MIL) is also on, obtain a reading of the trouble codes in the MOTRONIC system, see Service Manual 2:7 MOTRONIC 2.8.1 .

2. Connect the ISAT and select "MAIN THROTTLE POS" in the "OBTAIN READOUTS" menu. Drive the car and check that the ISAT shows about. 9%%at idling speed and about 70-92%% at full throttle.



3. If it does not, switch off the ignition and connect a BOB to the TCS control module. Start the engine and check whether the main throttle butterfly's position signal is present on pin 11 so that a reading can be obtained.


Correct readings are about 1.2 V when idling and about 2 V at 2500 rpm.

If the readings are incorrect, check the cable between pin 11 of the TCS control module and pin 54 of the MOTRONIC control module for continuity/shorting.

Remedy any defective cable.

4. Clear the code diagnostic trouble code. Start the car and drive it on test to check whether the diagnostic trouble code recurs. If it does, see "Before replacing a control module" for further measures.