P06C8 Cylinder 4 Glow Plug Incorrect
OBD-II Trouble Code Technical Description
Cylinder 4 Glow Plug Incorrect
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) and typically applies to OBD-II vehicles. That may include but is not limited to vehicles from VW, Audi, Ford, GMC, Ram, Chevy, etc. Anecdotally this code seems to be found mainly on Volkswagen / VW vehicles. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
When a code P06C8 is stored, it means that the powertrain control module (PCM) has detected an incorrect degree of resistance in the glow plug circuit for cylinder #4. Consult a source of reliable vehicle information to determine the location of the #4 cylinder for your year / make / model / powertrain configuration.
Diesel engines use high compression instead of spark to initiate piston movement. Since there is no spark involved, cylinder temperature must be increased to maximize compression. Glow plugs are used in each cylinder to accomplish this increase.
Often confused with spark plugs, a glow plug for each individual cylinder is threaded into the cylinder head. Battery voltage is applied to the glow plug element via a glow plug timer (sometimes called a glow plug controller or glow plug module) and/or the PCM. When voltage is correctly applied to the glow plug, it will literally glow red hot and aid in increasing cylinder temperature. Once cylinder temperature reaches the desired level, voltage is restricted by the control unit and the glow plug returns to it’s normal state.
If the PCM detects an unexpected resistance with the cylinder #4 glow plug, a code P06C8 will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Photo of a typical glow plug:
What is the severity of this DTC?
Any glow plug related code will likely be accompanied by drivability issues. A stored code P06C8 should be addressed with urgency.
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?
Causes for this P06C8 fuel injector code may include:
What are some P06C8 troubleshooting steps?
A diagnostic scanner, a reliable source of vehicle information, and a digital volt/ohmmeter (DVOM) will be required in order to arrive at an accurate diagnosis of a code P06C8. Use the vehicle information source to search for applicable technical service bulletins (TSB). If you locate a TSB that matches the vehicle make and model, symptoms exhibited, and the code stored, it will help you to arrive at a diagnosis.
You may also need to obtain diagnostic flow charts, wiring diagrams, connector face views, connector pin out charts, component locations, and component testing procedures/specifications from the vehicle information source. All this information will be needed to correctly diagnose the stored code P06C8.
After performing a careful visual inspection of all glow plug and glow plug control wiring and connectors, connect the diagnostic scanner to the vehicle diagnostic port. Now, retrieve all stored codes and freeze frame data and record it for later (just in case you need it). Next, I would test drive the vehicle to see if the code P06C8 is reset. Drive until one of two things happens: Either the PCM enters readiness mode or the code is reset. If the code is reset, continue with the diagnosis. If it is not, you are dealing with an intermittent condition which may have to worsen before an accurate diagnosis may be achieved.
Be careful not to burn yourself or start a fire when performing this test. My usual method to test glow plugs is to remove them and apply battery voltage. If the glow plug glows bright red, it is good. If the glow fails to heat up, it is defective. In the case of the stored code P06C8, you will want to take time to test it with your DVOM. If it does not comply with manufacturer’s specifications for resistance, consider it 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 a ground) at the glow plug connector (use the DVOM). If no voltage is present, test the power supply for the glow plug timer or glow plug controller. Test all related fuses and relays as recommended by the manufacturer. As a rule, I have found it best to test system fuses and fusible links with the circuit loaded. The fuse for a circuit which is not loaded may appear to be functional (when it is not) and lead you down the wrong diagnostic path.
If all fuses and relays appear functional, use the DVOM to test output voltage at the glow plug timer or PCM (wherever it originates). If voltage is detected at the glow plug timer or PCM, suspect that you have an open or shorted circuit. You may seek out the cause of the discrepancy or simply replace the circuit.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p06c8 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p06c8 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p06c8.
