Glow Plug/Heater Circuit "B"
P0382 indicates a malfunction in the glow plug heater circuit B, which is responsible for preheating the diesel engine cylinders for cold starts. The engine control module has detected a fault in the glow plug system's operation, performance, or electrical circuit.
What You Might Notice
- Glow plug indicator light stays illuminated longer than normal or remains solid
- Hard starting condition, especially in cold weather
- Engine cranks but hesitates to start
- Rough idle after cold start
- Reduced engine power during cold operation
Most Common Causes
- 1
Faulty glow plug
A glow plug in circuit B has failed or is not reaching proper operating temperature. Glow plugs typically last 100,000+ miles but can fail prematurely due to wear or electrical stress.
- 2
Glow plug wiring fault
The wiring harness to circuit B glow plugs has an open connection, short to ground, or poor contact. Wiring can corrode, loosen, or be damaged from engine heat and vibration.
- 3
Glow plug relay failure
The relay controlling circuit B glow plug power supply has failed or is stuck open. The relay may not be energizing the glow plugs when the engine control module commands them on.
- 4
Open or blown glow plug fuse
The dedicated fuse for glow plug circuit B is blown or the fuse holder connection is corroded. Check the fuse rating and replace with correct amperage if blown.
How to Diagnose It
- 1
Check Faulty glow plug — A glow plug in circuit B has failed or is not reaching proper operating temperature. Glow plugs typically last 100,000+ miles but can fail prematurely due to wear or electrical stress.
- 2
Check Glow plug wiring fault — The wiring harness to circuit B glow plugs has an open connection, short to ground, or poor contact. Wiring can corrode, loosen, or be damaged from engine heat and vibration.
- 3
Check Glow plug relay failure — The relay controlling circuit B glow plug power supply has failed or is stuck open. The relay may not be energizing the glow plugs when the engine control module commands them on.
- 4
Check Open or blown glow plug fuse — The dedicated fuse for glow plug circuit B is blown or the fuse holder connection is corroded. Check the fuse rating and replace with correct amperage if blown.
How to Fix It
- 1
Test and replace glow plugs
Remove glow plugs from circuit B cylinders and test resistance with an ohmmeter. Replace any glow plug showing infinite resistance or abnormally high resistance (typically should be 0.5-2 ohms cold). Install new glow plugs with correct heat range for your vehicle.
- 2
Inspect and repair glow plug wiring
Visually inspect the glow plug harness and connectors for corrosion, burnt terminals, loose connections, or damaged insulation. Clean corroded terminals with a wire brush, reseat loose connectors, and repair or replace damaged wiring sections.
- 3
Check and replace glow plug relay
Locate the glow plug relay in the engine bay fuse/relay panel using your owner's manual. Test the relay with a multimeter or swap with an identical relay to verify operation. Replace the relay if it fails to energize when powered.
- 4
Inspect glow plug fuse and circuit
Check the glow plug fuse in the main fuse panel for damage or blown element. Replace with the correct amperage rating if blown. If fuse blows again, a short in the glow plug circuit wiring exists and requires tracing and repair.
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