Code Definition

P066F — Cylinder 3 Glow Plug Control Circuit High

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P066F

P066F is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P066F is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a signal or supply voltage higher than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P066F is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P066F fault code is set when the Engine Control Module (ECM) detects a high voltage condition in the control circuit of the cylinder 3 glow plug. This condition indicates a potential electrical issue within the circuit. The ECM continuously monitors the voltage across the glow plug circuits. If the voltage in the cylinder 3 glow plug circuit exceeds a pre-set threshold for a given period, the ECM logs this code. This specific code focuses on the electrical characteristics of the control circuit, rather than the physical glow plug.

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