The P066A: Cylinder 1 Glow Plug Control Circuit Low code indicates that the control module has detected low voltage in the glow plug control circuit for cylinder 1. Glow plugs are essential for starting diesel engines, particularly in cold conditions. A low voltage condition can be caused by a faulty glow plug, wiring issues, or a problem with the glow plug control module.
P066A – Quick Overview
Code | Information |
---|---|
Meaning | P066A: Cylinder 1 Glow Plug Control Circuit Low |
Is it serious? | Yes, as it can lead to difficulty starting the engine, especially in cold conditions. |
Possible causes | – Low voltage in the cylinder 1 glow plug control circuit – Faulty glow plug – Wiring issue |
How to diagnose? | – Test cylinder 1 glow plug control circuit for voltage – Inspect wiring and connectors – Replace glow plug if necessary |
P066A Meaning
The P066A code indicates that the voltage in the control circuit for cylinder 1’s glow plug is lower than expected. The glow plug heats the cylinder for proper combustion during engine startup. If the control circuit has low voltage, it may prevent the glow plug from working efficiently, leading to hard starting or engine misfires.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional codes related to the glow plug system or electrical issues. These may help further diagnose the problem. | OBD-II Scanner |
Test the Cylinder 1 Glow Plug Control Circuit for Voltage | Use a multimeter to test the voltage in the glow plug control circuit for cylinder 1. Verify the voltage matches manufacturer specifications. | Multimeter |
Inspect Wiring and Connectors | Inspect the wiring and connectors leading to the cylinder 1 glow plug for damage, corrosion, or loose connections that could cause a drop in voltage. | Flashlight, Multimeter |
Test the Glow Plug | Test the glow plug itself to ensure it is heating correctly and is not faulty. If the glow plug is not functioning, replace it. | Diagnostic Tool, Multimeter |
Replace the Glow Plug if Necessary | If the glow plug for cylinder 1 is faulty or underperforming, replace it to restore proper starting performance, especially in cold weather. | Replacement Glow Plug, Tools |
Clear the Code and Test | After repairs, clear the code using an OBD-II scanner and test the vehicle to ensure the glow plug control circuit for cylinder 1 is functioning correctly. | OBD-II Scanner, Vehicle Manual |

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