P0691 BMW Fault Code
Check P0691 OBD Fault Code ReasonBMW Mass Air Flow (MAF) Sensor Intermittent The MAF sensor circuit is monitored by the PCM for sudden voltage (or air flow) input change through the comprehensive component monitor (CCM).
If during the last 40 warm-up cycles in key ON engine running the PCM detects a voltage (or air flow) change beyond the minimum or maximum calibrated limit, a continuous memory diagnostic trouble code (DTC) is stored.
P0691 Code Symptoms :
There are currently two main types of cylinder deactivation used today, depending on the type of engine. P0691 code for the pushrod design which uses solenoids to alter the oil pressure delivered to the lifters. In their collapsed state, the lifters are unable to elevate their companion pushrods under the valve rocker arms, resulting in valves that cannot be actuated and remain closed.
Diagnosis And Repairing P0691
P0691 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 P0691 code ?
- Failures of clutch motion/travel sensors.
- Faulty Variable Camshaft Timing (VCT) position solenoid
- Camshaft advance mechanism binding (VCT unit)
- Incorrect Positive Crankcase Ventilation (PCV) hose connection
Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code P0691, so consult the manual to locate the brake fluid reservoir.
Bear in mind that a low fluid level can set code P0691 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.
