Code
P0381
GWM
P — Powertrain
- Malfunction in circuit A of the glow plug indicator
AI status
Completed
Completed
100%
Causes
- Blown fuse for glow plug/indicator circuit
- Faulty glow plug indicator lamp or instrument cluster LED
- Open, shorted or corroded wiring/connectors in indicator circuit A
- Faulty glow plug relay or glow-plug control module
- High resistance in glow plug supply or ground (bad glow plugs, poor ground)
- ECM/PCM internal fault or incorrect driver output
Symptoms
- Glow plug warning/indicator lamp fails to illuminate or stays on continuously
- Longer cranking time and harder cold starts
- Glow-plug lamp behavior inconsistent or intermittent
- Possible illumination of MIL or other related engine warning lights
- Cold-start performance degraded
What to check
- Retrieve freeze frame and live data with a scan tool; record status of glow-plug control and indicator outputs
- Visually inspect fuses, relay(s) and connector(s) in the glow plug/indicator circuits for corrosion, damage or loose pins
- Check instrument cluster lamp function by commanding indicator on with scan tool (if supported) or by bench testing the lamp
- Measure battery voltage at relay/indicator harness with ignition ON
- Check ground integrity at instrument cluster, relay bracket and engine ground points
- Measure continuity/resistance of wiring between ECM, glow plug relay/control module and indicator lamp
Signal parameters
- Ignition ON: indicator circuit should show battery voltage at lamp feed (approx. system battery voltage) when lamp is commanded ON
- ECM driver pin: expected to switch to ground or supply (depends on vehicle design) to activate relay — verify with scope or multimeter
- When glow plugs are commanded ON: supply line to glow plugs should approach battery voltage and show significant current draw
- Individual glow plug resistances: usually low (often under a few ohms) — large variation or open circuit indicates failure; expect measurable continuity
- Relay coil resistance: should show continuity (no open) and switch continuity between supply and lamp/coil when energized
Diagnostic algorithm
- Connect a diagnostic scanner; confirm P0381 and note any related codes (P0380, P067x etc.). Clear code and attempt to re-create.
- Visually inspect fuses, glow-plug relay, harnesses and connectors related to the glow-plug and indicator circuits. Repair any damage or corrosion.
- With ignition ON, measure voltage at the indicator lamp terminal. Command the lamp ON with scan tool; verify lamp receives battery voltage and illuminates. If lamp does not light, bench-test lamp/LED or replace cluster lamp element.
- Check relay operation: with scanner command or ignition cycle, verify relay coil sees control signal from ECM and relay closes to supply the indicator/heat circuit. Replace relay if it fails to switch.
- Verify continuity and resistance between ECM, relay and instrument cluster. Repair any open or high-resistance wiring; ensure good grounds.
- Command glow plugs ON with a scan tool and measure voltage and current at the glow-plug supply and at each plug. Replace any glow plug with open or excessive resistance.
- If wiring, relay and glow plugs check good but fault persists, inspect ECM output pin for proper operation. Consider ECM reflash or replacement only after other components are confirmed good.
- After repairs, clear codes and perform multiple key cycles and cold-start tests to confirm the fault does not return.
Likely causes
- Corroded connector or poor ground at indicator/relay
- Faulty glow plug indicator lamp (burnt bulb/LED)
- Failed glow-plug relay or control module
- Damaged wiring harness between ECM, relay and indicator
Fault status
Status
Malfunction detected in glow plug indicator circuit A — ECM reports abnormal voltage/feedback, open, short or high resistance in the indicator/relay wiring or component.
Repair difficulty: Medium
Diagnostic time: 1-2 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email