P0382 – Glow Plug/Heater Circuit “B”

P0382 is a diagnostic trouble code that points to a problem in your diesel engine’s glow plug or glow plug heater circuit, usually on “Bank 2.” When this code sets, your engine computer has detected an electrical fault that affects cold starting and early warm-up. You might notice hard starting, rough idle, extra smoke, or the glow plug light staying on. While P0382 usually won’t leave you stranded in mild weather, ignoring it can shorten glow plug life, stress the starter, and make winter starts a real headache if you don’t address it properly.

What Does P0382 Mean?

P0382 is an OBD-II code that typically reads as “Glow Plug/Heater Circuit ‘B’ Malfunction” or “Glow Plug Heater Circuit Bank 2.” It applies mainly to diesel engines that use glow plugs or an intake heater to help the engine start and run smoothly when cold.

The ECU monitors voltage and current in the glow plug circuit. If it sees a value that’s too high, too low, or out of the expected range for a certain amount of time, it logs P0382 and usually turns on the check engine light or the glow plug warning lamp.

Quick Reference

• Code: P0382
• Meaning: Glow plug/heater circuit “B” or Bank 2 malfunction
• System: Diesel cold-start assist (glow plugs / heater)
• Severity: Moderate – worse in cold weather
• Typical Fixes: Glow plug(s), glow plug relay/module, wiring repair

Real-World Example / Field Notes

In the shop, I see P0382 most often on higher-mileage diesel pickups and vans as winter rolls in. A common scenario: you complain that the truck cranks longer in the morning, puffs white or gray smoke, and the glow plug light acts odd. A quick scan shows P0382 along with a stored history of hard cold starts. Testing usually finds one or more failed glow plugs on the bank near the passenger side, or a corroded connector in the harness. Fixing that bank’s glow plugs and cleaning the connectors typically restores normal cold starting.

Symptoms of P0382

• Hard cold starting – engine cranks longer than normal, especially in low temperatures.
• Rough idle when cold – shaky or uneven idle for the first minute or two after startup.
• Excess exhaust smoke – white or gray smoke on cold start due to incomplete combustion.
• Glow plug light issues – glow plug or preheat indicator stays on longer, flashes, or doesn’t come on as usual.
• Reduced cold-weather performance – sluggish throttle response until the engine warms up.
• Check engine light – MIL illuminated or stored code when scanned, even if the glow plug light seems normal.
• Occasional misfire when cold – one or more cylinders may feel like they “skip” briefly on first startup.

Common Causes of P0382

Most Common Causes

• Failed glow plug(s) on Bank 2: The heating element inside the glow plug burns out or goes open-circuit, causing abnormal resistance and triggering P0382.
• Glow plug relay or control module failure: The relay or solid-state controller that feeds power to Bank 2 can stick, fail internally, or lose output on one side.
• Wiring harness damage: Chafed, corroded, or broken wires between the relay/module and the Bank 2 glow plugs are very common on older diesel trucks and vans.
• Poor electrical connections: Loose, oxidized, or oil-soaked connectors at the glow plugs, relay, or ECU can raise resistance and upset the monitored current.
• Blown fuse or poor power supply: A dedicated glow plug fuse or fusible link may be partially failed or have poor contact, causing low voltage to Bank 2.

Less Common Causes

• Faulty coolant temperature sensor: If the ECU “thinks” the engine is warmer or colder than it is, it may command the wrong glow plug cycle and set a false P0382.
• ECU/PCM internal fault: Rare, but a failed driver circuit inside the engine computer can cause incorrect monitoring or power output to the glow plug circuit.
• Aftermarket modifications: Poorly installed remote start systems, performance tuners, or wiring add-ons can interfere with the glow plug control circuit.
• Incorrect or mismatched glow plugs: Using the wrong resistance or non-OE-style glow plugs can confuse the ECU’s current monitoring and trigger the code.

Diagnosis: Step-by-Step Guide

You’ll want a good scan tool (preferably with Mode $06 data), a digital multimeter, basic hand tools, and access to a wiring diagram or service information for your specific vehicle. A test light and an infrared thermometer can also help when comparing cylinder temperatures after a cold start.

1. Confirm the code and freeze-frame data. Connect a scan tool, read P0382, and note engine temperature, RPM, and battery voltage when the code set. Look for other glow plug codes like P0380 or cylinder-specific codes.
2. Visually inspect wiring and connectors. With the key off, inspect the glow plug harness on Bank 2. Look for brittle insulation, rubbed-through spots, green corrosion, loose connectors, or oil-soaked plugs.
3. Check power supply and fuses. Using a multimeter, verify battery voltage at the glow plug relay or control module input. Inspect and test glow plug fuses and fusible links under load.
4. Test glow plug resistance. Disconnect each Bank 2 glow plug. Measure resistance from the terminal to ground. Compare to spec (often around 0.4–1.0 ohms, but check your manual). Any plug reading open, very high, or very low compared to the others is suspect.
5. Check voltage at glow plugs during preheat. With a helper cycling the key to “ON,” measure voltage at a Bank 2 glow plug connector. You should see near-battery voltage for the preheat period. No voltage usually points to the relay/module or upstream wiring.
6. Test the glow plug relay or control module. Verify that the relay is getting a control signal from the ECU and that it outputs power to Bank 2. On solid-state modules, follow manufacturer test procedures or use scan tool bi-directional controls if available.
7. Use Mode $06 or live data if available. Some ECUs report individual glow plug current or status. Compare Bank 2 readings to Bank 1 to spot the outlier cylinder or a dead circuit.
8. Check related sensors. Verify coolant temperature sensor data on a cold engine. If it reads far off ambient temperature, it may be confusing glow plug operation.
9. Clear codes and perform a cold-start test. After repairs or tests, clear P0382 and let the vehicle sit until fully cold. Start it while monitoring data and see if the code returns.

Pro tip: When replacing glow plugs, test and compare all of them, not just the one that failed. On high-mileage diesels, it’s often smarter to replace the full bank (or all cylinders) to avoid repeated tear-downs.

Possible Fixes & Repair Costs

Fixing P0382 usually involves restoring proper power and resistance in the glow plug circuit on Bank 2. That can mean replacing failed glow plugs, repairing wiring, or swapping out a bad glow plug control module. Labor time varies a lot depending on engine layout and access to the plugs.

• Replace glow plug(s): Parts $20–$60 per plug, labor $80–$250 depending on access and number replaced.
• Replace glow plug relay/module: Parts $80–$300, labor $80–$200.
• Wiring/connector repair: Typically $100–$350 depending on how deep the harness damage goes.
• Sensor or ECU issues: Coolant temp sensor $100–$250 installed; ECU replacement/programming can run $500–$1,200+.

In most cases, you’re looking at a total repair cost in the $150–$600 range for a straightforward glow plug or relay fix. Costs rise with difficult access, seized glow plugs, or extensive wiring damage.

Can I Still Drive With P0382?

You can usually still drive with P0382, especially in mild or warm weather, but cold starts may be harder and rougher. The engine will often run normally once it warms up. However, repeated long cranking and poor combustion when cold can stress the starter, battery, and exhaust system. If you live in a cold climate or rely on your diesel daily, you should treat P0382 as a priority repair rather than something to ignore.

What Happens If You Ignore P0382?

If you ignore P0382, cold starts will likely get progressively worse as more glow plugs or wiring sections fail. You may end up with no-start situations in winter, increased white smoke, raw fuel in the exhaust, and extra wear on the starter and battery. In severe cases, unburned fuel can damage the diesel particulate filter or foul the exhaust system over time.

Last updated: March 1, 2026

Vehicles Commonly Affected by P0382

P0382 is most common on light-duty and medium-duty diesel vehicles. You’ll often see it on:

• GM/Chevrolet diesel trucks and vans – Duramax-equipped Silverado, Sierra, Express, and Savana models.
• Ford Power Stroke diesels – F-250, F-350, and E-series vans, especially older 6.0L and 7.3L engines.
• Dodge/Ram diesels – Cummins-powered Ram 2500 and 3500 trucks with aging glow plug systems.
• European diesel cars and vans – VW, Audi, Mercedes-Benz, BMW, and Sprinter vans frequently show glow plug circuit codes as they age.
• Asian diesel SUVs and pickups – Toyota, Nissan, Isuzu, and Mitsubishi diesels used in various markets.

While the exact layout and naming of “Bank 2” varies, the underlying issue—an electrical fault in the glow plug circuit—is similar across these platforms.