C0809 Diagnostic Trouble Code

C0809 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 C0809 diagnostic trouble code may include:

Possible spark knock (detonation / pre-ignition)
Poor fuel economy
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
Rich or lean exhaust

Possible Causes :

The Mass Airflow sensor will also cause this problem. Mass Airflow circuit malfunction.
Fuel with a large percentage of sulfur will clog the DPF quickly
Defective ECU strategies or components will prevent proper regeneration

Repair Processes :

Find out what kind of system you have and verify that voltage to the fuel level sensor is present at the fuel pump wiring harness. Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. 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.

Process Tips

Diagnostic trouble code C0809 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 C0809.

Fortunately, C0809 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

C0809 Trouble Code For Specific Cars

C0809 Du Pont Model Illuminated Entry Input Circuit Failure
C0809 Nissan Bluebird Climate Control Temperature Differential Circuit Failure
C0809 Austin A35 Autolamp Delay Increase Circuit Failure
C0809 Cadillac Bls Data Mismatch #2 (receive data does not match what was expected)
C0809 Zagato Zeta SCP (J1850) Invalid or Missing Data for Transmission / Transaxle / PRNDL
C0809 Seat Mii Injector High Side Short To GND Or VBATT - Bank 2
C0809 Peugeot 309 EGR Flow Out Of Self Test Range