C12E9 Diagnostic Trouble Code

C12E9 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 C12E9 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 :

Once located, visually inspect the connectors and wiring. Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code C12E9 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 C12E9.

Fortunately, C12E9 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C12E9 Trouble Code For Specific Cars

C12E9 Opel Antara Damper RR Circuit Short To Battery
C12E9 Daimler Light Heated Backlite Input Circuit Open
C12E9 Jaguar F-type Seat Driver Forward Switch Circuit Short To Battery
C12E9 Mazda Mx-6 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction
C12E9 Glas 3000 PAD Warning Lamp Inoperative
C12E9 Abarth Ot 1600 A/C Post Heater Sensor #2 Circuit Failure
C12E9 Morris Ten Four Cam Calibration Fault