Technical Description of OBD-II Trouble Code
Incorrect Glow Plug in Cylinder 9
What does that signify?
This is a generic diagnostic trouble code (DTC) that pertains to OBD-II vehicles. It may apply to various vehicles such as VW, Audi, Ford, GMC, Ram, Chevy, etc. 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 P06CD is stored, it indicates that the powertrain control module (PCM) has detected an incorrect level of resistance in the glow plug circuit for cylinder #9. To determine the location of the #9 cylinder for your specific vehicle, consult a reliable source of vehicle information.
In diesel engines, high compression is used instead of spark to initiate piston movement. Since there is no spark involved, the temperature of the cylinder must be increased to maximize compression. Glow plugs are used in each cylinder to achieve this temperature increase.
Glow plugs, which are often mistaken for spark plugs, are threaded into the cylinder head for each individual cylinder. The glow plug element receives battery voltage through a glow plug timer or the PCM. When voltage is correctly applied, the glow plug becomes red hot and helps increase the cylinder temperature. Once the desired temperature is reached, the control unit restricts the voltage and the glow plug returns to its normal state.
If the PCM detects an unexpected resistance in the glow plug for cylinder #9, it will store the code P06CD and may illuminate the malfunction indicator lamp (MIL).
Photo of a typical glow plug:
What is the severity of this DTC?
Any code related to glow plugs is likely to cause drivability issues. It is important to address a stored code P06CD promptly.
What are some of the symptoms of the code?
Symptoms of a P06CD trouble code may include:
What are some of the common causes of the code?
Possible causes for this P06CD code related to the glow plug may include:
What are some P06CD troubleshooting steps?
In order to accurately diagnose a code P06CD, 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.
You may also need to obtain additional information such as 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 of this information will be necessary for a correct diagnosis of the stored code P06CD.
After visually inspecting all glow plugs 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 future reference. Next, test drive the vehicle to see if the code P06CD is reset. Continue driving until either the PCM enters readiness mode or the code is reset. If the code is reset, proceed with the diagnosis. If not, you may be dealing with an intermittent condition that may need to worsen before an accurate diagnosis can be made.
Be cautious during the test to avoid burns or starting a fire. To test glow plugs, you can remove them and apply battery voltage. If the glow plug glows bright red, it is functioning properly. If it fails to heat up, it is defective. For the stored code P06CD, it is recommended to test it with a DVOM to check if it complies with the manufacturer’s resistance specifications. If it does not, consider it defective.
If the glow plugs appear to be working correctly, use the scanner to activate the glow plug timer and test for battery voltage (and a ground) at the glow plug connector using the DVOM. If there is no voltage, test the power supply for the glow plug timer or glow plug controller. Test all related fuses and relays as recommended by the manufacturer. It is best to test system fuses and fusible links with the circuit loaded to avoid diagnostic errors.
If all fuses and relays appear to be functional, use the DVOM to test the output voltage at the glow plug timer or PCM. If voltage is detected at the glow plug timer or PCM, suspect an open or shorted circuit. You can investigate the cause of the discrepancy or simply replace the circuit.
