B1408

Main Throttle Butterfly Position Signal, Faulty, Break/Short-Circuit

Fault Symptom
- TCS OFF lamp lit, Traction Control System (TCS) system not functioning and possibility of diagnostic trouble codes in the MOTRONIC

Conditions
- For diagnostic trouble code B1406:
Main butterfly position signal from pin 54 in the MOTRONIC control module to pin 11 in the TCS control module is faulty
- For diagnostic trouble code B1407:
Main butterfly position signal from pin 54 in the MOTRONIC control module to pin 11 in the TCS control module is shorted to ground
- For diagnostic trouble code B1408:
Main butterfly position signal from pin 54 in the MOTRONIC control module to pin 11 in the TCS control module is shorted to Batt+/broken

Action
1 If the CHECK ENGINE lamp is also lit when driving, read and act on diagnostic trouble codes in the MOTRONIC, refer to Powertrain Management.
2 Start the engine.
- Connect the ISAT and select the "MAIN THROTTLE POS" command in the OBTAIN READOUTS" menu.
- The ISAT should show approx. 9% when idling and approx. 92% at wide open throttle.
- If the values are correct, proceed to point 4.
- If the values are incorrect, proceed to point 3.
3 Conduct continuity test on the lead between pin 54 of the MOTRONIC control module and pin 11 of the TCS control module for breaks, shorts and bypasses.
- If the value is correct, proceed to point 4.
4 Erase the diagnostic trouble code, test-drive the car and see if the diagnostic trouble code is reregistered.
- If the trouble code is registered, proceed to Control Module, Procedure Prior To Replacement.
- If the diagnostic trouble code is not registered, the action taken was correct or the fault was of the intermittent type.