C0991 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 C0991

C0991 Code Symptoms :

The original multi-displacement system turned off opposite pairs of cylinders, allowing the engine to have three different configurations and displacements. C0991 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 C0991

C0991 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 C0991 code ?

• Exhaust tube
• Faulty spark plug (s)
• Intake Valve Timing Control Solenoid Valve circuit poor electrical connection
• Oil Control Valve (OCV) circuit is open or shorted

Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code C0991, so consult the manual to locate the brake fluid reservoir.

Bear in mind that a low fluid level can set code C0991 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.