B3977 BMW Fault Code

Description:

The issue covered by the bulletin involves a power steering noise/whine or fluid leak from the power steering pump, gear or high pressure side power steering hose during extreme low outdoor temperature operation.

B3977 Code Symptoms :

The original multi-displacement system turned off opposite pairs of cylinders, allowing the engine to have three different configurations and displacements. B3977 code had an elaborate diagnostics procedure, including showing engine trouble codes on the air conditionning display. However, the system was troublesome, misunderstood by customers, and a rash of unpredictable failures led to the technology being quickly retired.

Diagnosis And Repairing B3977

B3977 OBD 2 code on vehicles with electronically controlled automatic transmissions, the 3-4 shift solenoid is responsible for actuating the hydraulic circuits to activate clutches or bands that change gears inside the automatic transmission.

How to fix B3977 code ?

• Continuous oil flow to the VCT piston chamber
• Failures of clutch motion/travel sensors.
• EVAP system hose leaking
• Ignition coils circuit poor electrical connection

To check for an open circuit, trace along the length of the transmission control circuit, checking for breaks in the wiring. Repair any broken wiring and make sure all connectors are fully seated and locked.

Pay close attention to connectors, looking for corrosion, bent or broken pins, or moisture in the connector. Repair any connector issues even if they are not specifically part of the transmission control circuit as they may serve a function in providing power to the transmission control circuit.