Glow Plug Monitor Fault (Bank #2)
The engine computer detected a problem with the glow plug heating system on cylinder bank #2 (usually the side opposite the #1 cylinder). Think of glow plugs like tiny heaters in diesel engines that warm the combustion chamber before starting—if they're not working, the engine struggles to start in cold weather.
The ECM monitors the glow plug circuit voltage and current draw during the pre-heat phase before engine start. It detects open circuits, shorts, or insufficient heating resistance in the Bank #2 glow plug control circuit. If current or voltage falls outside acceptable limits, the fault is logged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Glow plug circuit voltage | 11-14V during pre-heat cycle | <8V or >15V, or no voltage detected |
| Glow plug current draw | 50-100A typical draw during warm-up | <10A or >150A indicating open or short |
Code P1401 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1401 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.