U1878 BMW Fault Code

Description:

Variable Cam Timing Over-advanced (Bank 1) The comprehensive component monitor (CCM) monitors the VCT position for an over-advanced camshaft timing.
The test fails when the camshaft timing exceeds a maximum calibrated value or remains in an advanced position.

BMW cam timing improperly set No oil flow to the VCT piston chamber Low oil pressure VCT solenoid valve stuck closed Camshaft advance mechanism binding (VCT unit) U1878 DTC is a check of the VCT unit.

U1878 Code Symptoms :

OBD U1878 code and tailpipe testing are two different approaches to identify vehicles in need of repair. The OBD system looks for broken or malfunctioning emissions control components and U1878, while tailpipe tests sample a vehicle's exhaust to see if it is above or below certain prescribed limits. Given the robust nature of today's emissions control components, it is entirely possible for an individual component to malfunction without leading to an immediate increase in emissions at the tailpipe.

In such cases, other components (like the catalyst) can temporarily compensate for the part that is broken however, these other components can only do double duty for so long before they, too, begin to malfunction. In addition, OBD also monitors for and other malfunctions in the fuel system problems that traditional tailpipe tests were not designed to identify. Most state and local areas also include a gas cap pressure test as part of an emission inspection.

Diagnosis And Repairing U1878

U1878 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 U1878 code ?

• Erratic camshaft position due to low oil pressure
• Engine Control Module (ECM)
• Intake Valve Timing Control Solenoid Valve circuit poor electrical connection
• Variable Valve Timing (VVT) 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 U1878, so consult the manual to locate the brake fluid reservoir.

Bear in mind that a low fluid level can set code U1878 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.