C157F Diagnostic Trouble Code

C157F is a kind of OBD-II Diagnostic C-Chassis Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a C157F diagnostic trouble code may include:

Faulty or damaged wiring
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly
Poor fuel economy
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

Possible Causes :

A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Faulty IMRC actuator relay (if equipped)
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.

Repair Processes :

Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications. Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector.

Process Tips

Diagnostic trouble code C157F is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before C157F.

Fortunately, C157F is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C157F Trouble Code For Specific Cars

C157F Rover 3.5-litre Ignition Coil - Cylinder 6 - Early Activation Fault
C157F Chrysler Neon Evaporative Emission Control System Vent Control Circuit Malfunction
C157F Ds Ds 5 Ignition/Distributor Engine Speed Input Circuit Malfunction
C157F Bristol 403 Cooling Fan Power/Ground Circuit Malfunction
C157F Packard 300 DPFE Circuit Low Input
C157F Skoda Superb Ii Lack Of HO2S21 Switch - Sensor Indicates Lean
C157F Mercedes S 280 Accessory Delay Relay Contact Short To Battery