B3906 BMW Fault Code

Description:

The Transmission Fluid Pressure Switch allows the engine's control module (PCM) or Transmission Control Module (TCM) to use hydraulic fluid to engage the clutches in the transmission to allow for smoother shifting while driving. If the PCM or TCM detects an issue with the hydraulic clutch or the pressure switch, the BMW PCM or TCM will set code B3906

B3906 Code Symptoms :

The scent may B3906 signal oil or coolant leaking from their normally closed-loop systems, or it may indicate dangerous exhaust gases invading your car's interior. Car and truck exhaust contains toxic gases such B3906, so if the inside of your car as if you were standing behind your car, get out and get it fixed.
Fight the urge to take a little nap first. So sleepy. That's the carbon monoxide talking, friends. At least open a window on your way to the shop.

Diagnosis And Repairing B3906

Parts or components should not be replaced with reference to only a B3906 DTC. The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing.

How to fix B3906 code ?

• Exhaust tube
• Faulty oil control valve (OCV)
• Failures of clutch motion/travel sensors.
• Failures of clutch motion/travel sensors.

A good starting point in your diagnosis is checking all system fuses and fusible links. This can be done using the BMW DVOM on the voltage setting. You will want to test the fuses with circuits loaded.

Some fuses will appear normal until a load is placed on their respective circuit; at which point they will fail. This has been the cause of many 'phantom malfunctions'. Consult your vehicle information source for fuse and fusible link locations. If all fuses are in working order, you may want to check TCM relay operation by swapping identical relays. Usually the horn relay, starter relay, fuel pump relay, air conditioning clutch relay, and controller relays are similar enough in design to swap for diagnostic purposes.