This code indicates that the powertrain control module (PCM) has detected an implausible or out-of-range signal during communication with the glow plug control module (GPCM). The issue is not the glow plugs themselves but rather the data exchange or signal quality on the dedicated communication circuit between the two controllers. It typically results in hard cold starts and illumination of the check engine light.
The GPCM contains the communication circuitry that reports glow-plug status and current draw to the PCM. Internal driver or logic faults can send out-of-range or corrupted data, causing the PCM to set a range/performance fault.
Corrosion, moisture intrusion, chafing, or poor pin fit in the harness between the GPCM and PCM can introduce resistance or intermittent opens. This distorts the serial communication signal and produces a range/performance error rather than a total communication loss.
High resistance or voltage drop in the module’s battery feed or ground paths can cause erratic internal operation. Low supply voltage may shift communication line voltages out of the expected range.
A shorted glow plug or harness fault on the high-current output side can overload the GPCM internal drivers. The resulting voltage sag or thermal protection event may corrupt the module’s data output to the PCM.
A rare failure of the PCM’s communication receiver or input processing logic can incorrectly interpret valid GPCM data as out of range. This should only be considered after the module, wiring, and power supplies are proven sound.
Short trips are usually possible, but hard starting in cold weather and increased emissions make prompt repair advisable. In freezing conditions the engine may fail to start.
No. The root cause is almost always the glow plug control module or the wiring between modules. PCM failure is uncommon and should not be assumed without thorough testing.
The replacement module can be damaged by an underlying glow-plug short, or an unnoticed harness fault can continue to corrupt the communication signal. Always test the glow-plug circuits and wiring before and during module replacement.
Not necessarily. The code targets module-to-computer communication, but testing the glow-plug circuits is important because a shorted plug can damage the control module and distort its data output.