B1781 BMW Fault Code

Description:

Intake Manifold Runner Control Malfunction (Stuck Open) The IMRC system is monitored for failure during continuous, key ON engine OFF or key ON engine running self-test. The test fails when the signal on the monitor pin is less than an expected calibrated range at closed throttle. IMRC monitor signal circuit shorted to BMW PWR GND or SIG RTN Damaged IMRC actuator Damaged PCM An IMRCM PID reading approximately near 1 volt at closed throttle may indicate a fault.

B1781 Code Symptoms :

The original multi-displacement system turned off opposite pairs of cylinders, allowing the engine to have three different configurations and displacements. B1781 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 B1781

B1781 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 B1781 code ?

• EVAP canister or fuel tank leaks
• Failures of clutch motion/travel sensors.
• Faulty Variable Camshaft Timing (VCT) position solenoid
• Dirty Oil

Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code B1781, so consult the manual to locate the brake fluid reservoir.

Bear in mind that a low fluid level can set code B1781 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.