P066D OBD Error Code: Problem & Solutions

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What causes a P066D error code? How to get rid of them? Are you looking for these answers, then keep reading.to preheat the cylinder before engine start, glow plugs are used? If the engine control module detects that the glow plugs for cylinder 1 is not operative, then the P066D code will be set by PCM.

High compression is used by diesel engine to start piston movement instead of stark. As there is no spark involved, cylinder temperature must be improved to exploit compression. Glow plugs are used in each cylinder to achieve this. A glow plug for each separate cylinder is eased into the cylinder head. Battery voltage is applied to the glow plug element through glow plug timer also known as a glow plug controller or glow plug module. When voltage is properly applied to the glow plug, it will exactly glow red hot and helps to increase cylinder temperature. Once it reaches the level, the voltage is shut and the glow plug turns normal.

What causes this problem with the Cylinder 2 Glow Plug Control Circuit High?

• Glow plug is poor.
• Opening or glow plug control module is shorted.
• Glow plug connector is defective.
• Glow plug timer is damaged.

1. Power Control Module - Experiencing any problem with PCM? Then it’s a best choice to get them replaced.
2. Engine Control Module - Engine control module has to function effectively in order to avoid this error. So, get the component replaced.
3. Glow Plug - A faulty glow plug will not glow brightly. Replace them to glow bright red.
4. Glow Plug Relay - check the connection of the glow plug relay. If they are not proper, disconnect and reconnect them.
5. Glow Plug Control Module - If the glow plug control module is damaged, it will misbehave. Replace them to avoid P066D error code.
6. Glow plug wiring harness - any damage to the wire joints will result in oily leaks. Carefully inspect and fix the issue.

After knowing all the cause behind the issues, let’s have a look at few common symptoms of this problem. Read through this section to learn more about this error code.

Common Symptoms

• More black smoke from exhaust.
• Issues with engine.
• Engine delays during start-up.
• Less fuel efficiency.
• Presence of engine misfire codes.

Want to correct the Trouble Code P066D? Read these points mentioned below:

• Substituting the glow plugs.

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P066D code to be stored:

• A diagnostic scanner, a reliable source of vehicle information, and DVOM will be needed to diagnose P066D code. Find the right TSB that matches with your vehicle make, model as it can help you to identify the stored error codes and perform diagnosis.
• Also, you have to obtain other diagnostic information like diagnostic flowcharts, wiring diagrams, connector face views, component locations, and component testing procedures to diagnose P066D code.
• Visually inspect the glow plug, control wires, glow plug connectors. Connect the diagnostic scanner and recover all stored codes and data. Test drive to see if the code returns. Either PCM enter readiness mode or code will be reset. If any of these 2 happens, continue diagnosing. Else, there will be irregular connection where you have to worsen the situation before diagnosing.
• The best choice is by removing the glow plugs and applying battery voltage. Bright red glow indicates it is good, if not test it with DVOM and you will notice that it does not meet requirements as specified by manufacturer.
• If the plugs work properly, test the battery for voltage with DVOM. If voltage is absent, check power supply for glow plug controller/ timer. It’s best to test all the fuses, relays, connected circuits with loaded circuit. The circuit may appear to function normally which leads to wrong path.
• Use the DVOM to test output voltage if all the fuses and relays function properly. Presence of voltage in the glow timer indicates that there in an opening or short circuit. Replace them as desired.
• A defective glow plug cannot be the only reason for P066D error code in the system. It can also rise due to changes in the control circuit.
• Trying to diagnose the wrong cylinder is one common error. Make sure you start diagnosing the right one before proceeding.

Common Mistakes When Diagnosing the P066D Code

• Glow plug control module damage.
• Glow plug damage.
• Glow plug relay damage.
• Glow plug wiring harness damage.