P0382
Glow Plug/Heater CircuitBP0382 is a generic OBD-II powertrain diagnostic trouble code: Glow Plug/Heater CircuitB. It is logged by the engine control unit when the glow monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0382 means
P0382 — "Glow Plug/Heater Circuit \"B\" Malfunction" — is stored when the Engine Control Module (ECM) detects a fault in the glow plug control circuit designated as bank \"B.\" Glow plugs are electrically-heated metal rods threaded into diesel engine combustion chambers; they pre-heat the air charge during cold starts to allow the compression-ignition process to occur without excessive cranking. On V6, V8, and some inline diesel engines, the ECM may manage two separate glow plug banks — bank \"A\" (typically cylinders 1, 3, 5 on the first bank) and bank \"B\" (cylinders 2, 4, 6 on the second bank). P0382 is the bank B counterpart to P0380, which covers bank A.
The ECM monitors the glow plug circuit via a dedicated controller or relay that feeds current to the plugs. When the module commands the bank B circuit on and measures abnormal current draw — such as an open circuit (no current), a short, or a failed relay preventing power delivery — it sets P0382. On vehicles with individual plug monitoring, even a single faulty plug on the bank B side can trigger this code. Cold-weather starting symptoms are the primary complaint, as weakened pre-heating causes slow ignition of the air-fuel mixture at low ambient temperatures.
P0382 is a diesel-specific code and will not appear on gasoline engines. Diagnosis should prioritise the glow plugs themselves (high failure rate on high-mileage diesels), the relay or control module, and the wiring harness feeding the bank B bus bar. Always check for companion codes such as P0380 (bank A) or P0384 (glow plug relay circuit) to determine whether the fault is isolated to bank B or is part of a broader glow system failure.
Common causes
Most-frequently reported root causes when P0382 is logged.
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1
One or more failed glow plugs on bank \"B\" — failed internal element causing an open or short in the circuit.
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2
Faulty glow plug relay or glow plug control module not energising the bank \"B\" circuit.
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3
Open circuit or broken wire in the bank \"B\" glow plug feed wiring or bus bar.
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4
Corroded, loose, or damaged connectors at the glow plug terminals or relay socket.
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5
Blown fuse in the glow plug power supply circuit for bank \"B\".
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6
Short to ground in the bank \"B\" wiring harness causing excessive current draw.
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7
Faulty ECM output driver for the glow plug relay control signal.
Symptoms drivers notice
How to diagnose P0382
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scan tool and retrieve all stored and pending codes; note whether P0380 (bank A) or relay codes (P0384) are also present.
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2
Inspect the fuse for the bank \"B\" glow plug circuit and replace if blown.
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3
Test the glow plug relay operation — apply 12V to the control coil and confirm the output circuit closes; replace if faulty.
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4
Measure current draw on the bank \"B\" circuit during the preheat phase using a clamp-on ammeter — a healthy bank draws approximately 15–25 A per plug initially, dropping as plugs reach temperature.
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5
Test each bank \"B\" glow plug resistance with a multimeter (connector unplugged) — a healthy plug typically reads 0.5–2 ohms; open circuit (OL) or near-zero ohms indicates a failed plug.
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6
Inspect the bank \"B\" wiring harness and bus bar for corrosion, cracked insulation, or loose terminal connections.
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7
If plugs, relay, and wiring test good, verify ECM glow plug control signal output before condemning the module.
Related powertrain codes
Frequently asked questions
What is the difference between P0380 and P0382?
Both codes relate to the diesel glow plug heating system. P0380 covers glow plug/heater circuit \"A\" (the first bank), while P0382 covers circuit \"B\" (the second bank). On V6 and V8 diesel engines the two banks are split across the two cylinder banks. If both codes are present simultaneously, the fault is likely in the shared relay, control module, or power supply rather than individual plugs.
Can P0382 cause a no-start in cold weather?
It significantly increases the risk. With bank B glow plugs not heating, the affected cylinders start cold and may not fire reliably until compression heat builds up. In very cold conditions (below -10°C / 14°F) a no-start is possible, especially on older or higher-compression diesels.
How do I know which specific glow plug on bank B has failed?
Disconnect the bank B feed wire and test each plug individually with a multimeter from the plug terminal to the engine block ground. An open circuit (infinite resistance) or a dead short identifies the failed plug. Many modern diesel ECMs with per-cylinder monitoring will store individual cylinder sub-codes alongside P0382.
Is P0382 serious enough to stop driving?
Once the engine is fully warm, the glow plugs are not in use and driveability is typically unaffected. The primary risk is difficulty restarting after a warm engine cools down in cold weather. Repair urgency increases significantly in winter months or cold climates.
Disabling P0382 in software
RaceTune can permanently disable P0382 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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