Code Definition

P066D — Cylinder 2 Glow Plug Control Circuit High

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

About P066D

P066D 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 P066D 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 P066D 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 P066D fault code is set when the Engine Control Module (ECM) detects a high voltage condition in the control circuit of the cylinder 2 glow plug. This typically indicates an electrical fault within the circuit. The ECM monitors the voltage in the glow plug circuit, and when the voltage exceeds a predetermined threshold for a specific duration, this code is triggered. It is important to note that this condition relates specifically to the control circuit, rather than the glow plug itself.

Quick Facts