Diesel Trouble Codes

P0380 — Glow Plug/Heater Circuit Malfunction — 5.9 Cummins Common Rail

P0380 is a generic OBD-II code for a glow-plug/heater circuit electrical fault detected by the ECM. On the 2003-2007 5.9L Cummins Common Rail this code does…

Updated October 15, 2026

What it means

The ECM has detected an electrical fault in a heater-type circuit. On this platform the engine uses an intake-air grid heater for cold start and has NO glow plugs. Therefore P0380 is not applicable to the 5.9L Cummins Common Rail hardware as defined; the code is a generic mismatch for this engine family.12

Most likely causes

  1. Code mis-match / generic definition not supported by platform hardware — Cold start: intake-air grid heater. NO glow plugs. The generic P0380 definition refers to a glow plug heater circuit, which this engine does not have.12
  2. ECM/PCM software or scan-tool misinterpretation — A generic OBD-II reader may report P0380 on a platform where no glow-plug circuit exists, leading to a false positive. No glow plugs are fitted.12
  3. Wiring harness / connector issue causing ECM to see an unexpected heater circuit fault — Although the engine has no glow plugs, the ECM monitors heater-type circuits such as the intake grid heater. An open/short in related heater wiring can trigger a generic heater-circuit DTC on some tools. Grid heater presence and no glow plugs.12

How to diagnose

  1. Verify platform and code applicability: confirm vehicle is 2003-2007 Dodge Ram 2500/3500 ISB 5.9 Common Rail with intake grid heater and no glow plugs.
  2. Check scan tool data and code definition source; confirm P0380 is being reported as generic glow plug/heater circuit malfunction.
  3. Inspect ECM freeze frame and related heater circuit monitors; look for grid heater relay, intake air heater, or other heater-type circuits that could be mis-identified. Cold start uses grid heater, no glow plugs.
  4. Inspect wiring and connectors for the intake grid heater circuit for opens, shorts, or high resistance; verify relay and fuse condition. Grid heater exists.
  5. If no actual heater circuit fault is found and engine starts/ runs normally in cold conditions, treat P0380 as non-applicable to this platform and clear the code; monitor for reoccurrence with a Cummins-specific scan tool.

Specs and test values

CheckNormal readingWhen to measureSource
Battery and charging voltage12.6–12.7 V at rest when fully charged; about 13.5 V runningEngine off, then running with loads onDieselHub

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Shop diagnosis—1–2 hrsShop
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
Intake grid heater relay$40–$1500.5–1 hrsEasy DIY

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 persists with a Cummins-specific tool, or if cold-start performance is poor, have a diesel technician verify grid heater operation and ECM calibration. Do not attempt high-pressure fuel system service for this code.

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

  1. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎

Repair videos: P0380 on the 5.9 Cummins CR

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