P0672: open circuit detected on cylinder 2 glow output

The cited P0672 strategy checks cylinder 2's glow output for an open load. Hardware assesses the circuit attached to the controller, so the code does not independently identify which part of that path is disconnected.

Understand the limits of the resistance evidence

The table requires open-load detection at a 200-kilohm condition and prohibits that detection below 16 ohms. It does not provide a single universal trip point throughout the gap between those values. Applying 16 ohms as a normal-plug specification would go beyond the source.

The diagnostic is filtered through ten failed samples among twenty, with a 100 ms function task. Type B reporting and glow-lamp indication are listed, rather than an immediate inference from one isolated reading.

The monitor must be eligible

Required conditions include engine running without cranking, battery voltage in range, no glow-system supply fault and duty cycle between 2.50% and 97.50%, with diagnostics enabled. A supply problem can prevent this individual output assessment, so the absence of a new code in that state is not a passing test.

For verification, identify the cylinder-2 circuit using vehicle-specific information and establish normal loading during an eligible interval. The source contains no component location or removal procedure and does not justify replacing every glow plug. Circuit isolation and any physical service must follow the appropriate workshop instructions.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1239.