Technical Description of OBD-II Trouble Code
Incorrect Glow Plug in Cylinder 4
What does that signify?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles, including VW, Audi, Ford, GMC, Ram, Chevy, and others. However, it is commonly found in Volkswagen / VW vehicles. The specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
When the code P06C8 is stored, it means that the powertrain control module (PCM) has detected an incorrect level of resistance in the glow plug circuit for cylinder #4. To determine the location of cylinder #4 in your vehicle, consult a reliable source of vehicle information.
In diesel engines, glow plugs are used to increase cylinder temperature and maximize compression, as there is no spark involved. Each cylinder has a glow plug threaded into the cylinder head, and when voltage is correctly applied, the glow plug will glow red hot and aid in increasing cylinder temperature. If the PCM detects an unexpected resistance with the glow plug in cylinder #4, the code P06C8 will be stored and the malfunction indicator lamp (MIL) may illuminate.
Photo of a typical glow plug:
What is the severity of this DTC?
A code related to glow plugs is likely to cause drivability issues. It is important to address a stored code P06C8 promptly.
What are some of the symptoms of the code?
Symptoms of a P06C8 trouble code may include:
What are some of the common causes of the code?
Possible causes for this P06C8 code may include:
What are some P06C8 troubleshooting steps?
To accurately diagnose a code P06C8, you will need a diagnostic scanner, a reliable source of vehicle information, and a digital volt/ohmmeter (DVOM). Use the vehicle information source to search for applicable technical service bulletins (TSB) that match the vehicle make, model, symptoms, and stored code. This information will help in the diagnosis process.
After visually inspecting the glow plug and glow plug control wiring and connectors, connect the diagnostic scanner to the vehicle diagnostic port. Retrieve all stored codes and freeze frame data, and record them for reference. Test drive the vehicle to see if the code P06C8 is reset. If it is reset, continue with the diagnosis. If not, you may be dealing with an intermittent condition that requires further monitoring.
Be cautious when performing tests involving glow plugs to avoid burns or fires. Test the glow plugs by applying battery voltage and checking if they glow red. If they do not comply with manufacturer’s resistance specifications, they are defective.
If the glow plugs appear to be working properly, use the scanner to activate the glow plug timer and test for battery voltage and ground at the glow plug connector using the DVOM. If no voltage is present, test the power supply for the glow plug timer or glow plug controller, and check all related fuses and relays as recommended by the manufacturer.
If all fuses and relays are functional, use the DVOM to test output voltage at the glow plug timer or PCM. If voltage is detected, there may be an open or shorted circuit that needs to be addressed.
