The glow plug for cylinder 5 isn't heating up properly, which makes diesel fuel harder to ignite in cold starts. Think of it like a lighter that won't spark—the engine struggles to fire up.
The ECU monitors voltage and current draw through the cylinder 5 glow plug circuit during the glow plug pre-heat phase. It detects open circuits, shorts to ground, or excessive resistance that indicates a failed plug or wiring fault. The circuit is typically commanded on for 1–10 seconds before engine start, depending on coolant temperature.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Glow plug circuit current | 8–15 amps during preheat | Below 2 amps or no current detected |
| Circuit voltage drop | 0.5–2 volts across relay/plug | Above 3 volts or open circuit |