B3791 BMW Fault Code

Description:

Output Shaft Speed sensor circuit intermittent failure The output shaft speed sensor signal to the PCM is irregular or interrupted.
Harness connector not properly seated Harness intermittently shorted, or open Harness connector damaged OSS sensor damaged, or not installed properly Verify harness and connector integrity Verify OSS sensor proper installation.

B3791 Code Symptoms :

There are currently two main types of cylinder deactivation used today, depending on the type of engine. B3791 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 B3791

B3791 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 B3791 code ?

• EVAP system hose leaking
• Faulty Mass Air Flow (MAF) sensor
• Improper ignition timing
• Faulty TCM or TCM programming

Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code B3791, so consult the manual to locate the brake fluid reservoir.

Bear in mind that a low fluid level can set code B3791 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.