C0042 Diagnostic Trouble Code

C0042 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 C0042 diagnostic trouble code may include:

Lack of power
Faulty O2 Sensor
Poor acceleration
Engine surge

Possible Causes :

Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.
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 :

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. If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.

Process Tips

Diagnostic trouble code C0042 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 C0042.

Fortunately, C0042 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C0042 Trouble Code For Specific Cars

C0042 Alfa Romeo 4c Accelerometer Front Circuit Failure
C0042 Volkswagen 1500 Rear Cargo Door Unlock Circuit Open
C0042 Lexus Lf TCM Power Relay Sense Circuit Low
C0042 Audi Rs3 ASM Mode Circuit [Perf / Winter / Sport / etc]
C0042 Renault Argos Gear Shift Foward Actuator Circuit High
C0042 Nissan Figaro Clutch position ckt short to ground
C0042 Dodge Aspen Ignition Coil B Primary/Secondary Circuit Malfunction