Guide To P066A OBD Error Code Solutions

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Do problem arise in your system due to glow plugs? Is the control circuit high? Then you’re more likely to experience P066A error code. Glow plugs are used to preheat the engine before they start up in diesel engines. If the glow plugs for cylinder 1 does not function properly, then the (PCM) will set the code P066A.

In order to start combustion during cold temperature the glow plugs help in providing heat. The glow plugs are heated during initial engine operation, before and during cranking. The ECM (engine control module) monitors the coolant temperature and glow plug voltage by controlling the ON time of glow plugs. There are 8 individual glow plug supply circuits in the California glow plug system between the controller and glow plugs. If the feedback voltage is not within range, the OBD II code is set.

What causes this problem with Cylinder 1 Glow Plug Control Circuit Low?

• Poor glow plug/s.
• Glow plug control circuit is open or shorted.
• Glow plug connector is faulty.
• Malfunctioning glow plug timer.

1. Powertrain Control Module - A faulty or broken PCM needs immediate replacement in order to avoid this error code.
2. Engine Control Module - P066A code can appear if there is a faulty ECM. Fix them as soon as possible
3. Glow Plug - If the glow plugs don’t light properly, then it can be poor. Get the right glow plugs from Parts Avatar.
4. Glow Plug Relay - A damaged glow plug relay, can be one of the reasons for this error. Replace the damaged part immediately.
5. Glow Plug Control Module - A damaged/ broken/ faulty Glow Plug Control Module has to be replaced or fixed to avoid this error code.
6. Glow plug wiring harness - Do you see any oil leaks in the wiring joints? If so clean them as desired so that it functions normally.

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

• Extreme black smoke from exhaust.
• Drivability issues in the engine.
• Late engine starts up.
• Less fuel efficiency.
• Misfire codes of engine may be stored.

Have a look at some ways with which you can correct the P066B code:

• Replacing the Glow plugs

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Here are some steps which you should follow in order to diagnose this fault code:

• To accurately diagnose P066A code you will need a diagnostic scanner, a reliable source of vehicle information, and a digital volt/ohmmeter (DVOM). Find an exact TSB that matches your engine make and model and locate it to find the shown symptoms and stored codes.
• You will need diagnostic flowcharts, wire diagrams, connector face views, connector pinout charts, component locations, and component testing procedure from the vehicle information source. This info can help you to correctly diagnose P066A code.
• Once you inspect all the glow plugs and its control wires, connectors, connect the diagnostic scanner to the diagnostic port of vehicle. Recover all the stored codes and freeze the frame data. Test drive your car to see if the code is reset. Proceed driving either if the PCM enters readiness mode or continue with diagnosis if the code is reset. If not so, there is irregular connection and you have to worsen the condition.
• A best way to test the plug is to remove them and apply battery voltage. If it is bright red, condition is good. If it fails to heat, test it with DVOM. Be careful not to burn or initiate a fire when proceeding this test.
• If the plugs work normal, activate the timer and test the battery for voltage. If there is no voltage, glow plug timer/ controller for power supply. As per manufacturer’s suggestion, test the fuse and relays with the circuit loaded. The unloaded circuit of a fuse will functional normally and lead you to wrong path.
• If both the fuse and relay functional normally, use DVOM to test output voltage. If you detect the voltage at the glow plug timer, PCM then there can be an open circuit. Simply replace them. A P066A code cannot be cause by a bad glow plug as it is related to control circuit code. A bad glow plug can cause an error code.
• One of the common issues is diagnosing the wrong cylinder. Before you start diagnosing make sure you diagnose the right cylinder.

Common Mistakes When Diagnosing the P066A Code

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