U0646 BMW Fault Code

Description:

BMW 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.

U0646 Code Symptoms :

When you turn on the ignition, the Service Engine Soon or Check Engine U0646 light should flash briefly, indicating that the OBD system is ready to scan your vehicle for any malfunctions. After this brief flash, the light should stay off while you drive as long as no problems are detected. If so, you'll be glad to know that your vehicle is equipped with an early warning system that could save you time, money, and fuel in addition to helping protect the U0646!

Diagnosis And Repairing U0646

U0646 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 U0646 code ?

• Failures of clutch motion/travel sensors.
• Failures of clutch motion/travel sensors.
• Erratic camshaft position due to low oil pressure
• EVAP canister or fuel tank leaks

Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code U0646, so consult the manual to locate the brake fluid reservoir.

Bear in mind that a low fluid level can set code U0646 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.