P0380 — Glow Plug/Heater Circuit Malfunction — 5.9 Cummins 24-Valve (VP44)

P0380 is a generic OBD-II code for a glow plug/heater circuit electrical fault. On the 5.9L Cummins 24-Valve VP44 platform the engine uses an intake-air grid…

Updated October 15, 2026

What it means

The ECM has detected an electrical fault in the glow plug/heater circuit. The generic definition is an electrical fault in the glow plug heater circuit. On this platform the cold-start system is an intake-air grid heater with no glow plugs. Therefore P0380 does not correspond to glow plugs on this engine; it is effectively a non-applicable/misapplied code for the engine hardware, and any setting is due to ECM monitoring of the heater circuit or a data/communication issue.¹

Most likely causes

1. Code not applicable to engine hardware; platform uses grid heater, no glow plugs — The 5.9L Cummins 24-Valve VP44 uses an intake-air grid heater and has no glow plugs or glow-plug control module. The generic P0380 definition refers to a glow plug heater circuit, which does not exist on this engine.¹
2. ECM heater-circuit monitoring fault / wiring issue to grid-heater relays — P0380 is defined as an electrical fault in the glow plug/heater circuit detected by the ECM. On this platform the only heater is the grid heater; a wiring/relay fault in that monitoring path can cause the generic code to set.¹
3. ECM internal fault or communication error causing spurious code — ECM internal issues can produce unrelated diagnostic trouble codes. Platform ECM-related codes include P0602 Control Module Programming Error and P0605 Internal Control Module ROM Error, showing ECM faults are recognized on this platform.²³

How to diagnose

1. Verify platform hardware: confirm 5.9L Cummins 24-Valve VP44 with intake grid heater and no glow plugs.
2. Check for other active codes. VP44-specific faults include P0216 Injection Timing Control Circuit Malfunction and P1688 Fuel Injection Pump Encoder Circuit Malfunction; unrelated heater codes suggest a non-engine cause.
3. Inspect grid-heater relays, wiring, and connections for opens/shorts that could trigger heater-circuit monitoring faults. P0380 generic definition is an electrical fault in the glow plug/heater circuit.
4. Review ECM health. If multiple unrelated codes are present, consider ECM internal faults such as P0602 or P0605.

Specs and test values

Parts and tools you may need

• Digital multimeter
• Wiring diagram for 1998.5–2002 Ram 2500/3500 Cummins
• Scan tool capable of reading Chrysler enhanced codes

Tools you’ll need

• digital multimeter — Checks continuity and voltage at the grid-heater relays and wiring to confirm the heater-circuit electrical fault flagged by P0380.
• OBD-II scan tool — Reads P0380 and any accompanying VP44 codes to verify the code is spurious and assess ECM health.
• wiring diagram — Confirms the 5.9L Cummins 24-Valve uses an intake grid heater with no glow plugs and shows the heater-circuit monitoring path.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the code returns with no grid-heater wiring fault, have a diesel technician evaluate ECM integrity and network communications. Do not attempt high-pressure fuel system service. Seek professional diagnosis for persistent or multiple ECM-related codes. This guide is diagnostic only. If safety-critical systems are involved, stop and consult a qualified professional.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

Repair videos: P0380 on the 5.9 Cummins 24V

Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.

Dodge Cummins Bad Grid Heater Relay Diagnosis + Fix — Schneids15 · 162K views

99 Dodge Cummins Preheat Not Working — Flippin Customized · 16K views