Glow Plug Monitor Fault (Bank #1)
The engine's glow plug system for diesel combustion isn't working properly on cylinder bank 1. Think of glow plugs like a lighter for your diesel engine—if they fail, the engine struggles to start, especially in cold weather.
The ECM monitors glow plug resistance and heating time before fuel injection. It checks that plugs reach target temperature within a specific window and verifies current draw stays within normal limits. If resistance is too high or heating time exceeds threshold, a fault is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Glow plug resistance | 0.5–2.0 ohms per plug | >2.5 ohms or open circuit |
| Preheat time to ready | 3–8 seconds at startup | >10 seconds or timeout |
Code P1400 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, P1400 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.