One or more failed glow plugs on circuit B (open circuit or high resistance); Corroded, loose or damaged wiring or connectors between the glow plug control module and the plugs; Faulty glow plug control module or relay, or its driver stage; Poor power or earth supply to the glow plug module, or a blown fuse; Short to earth or to supply in the circuit B wiring; Fault in the engine control unit output or communication with the glow plug module.

P0382

Glow Plug/Heater Circuit B.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
82: FaultThe specific fault in that area

What it means

P0382 is the generic code for a fault in glow plug/heater circuit B. The engine control unit (or glow plug control module) monitors the glow plug circuit and saw a voltage, current or feedback signal outside the expected range. Which cylinders sit on circuit 'B' and how the circuit is monitored depends on the engine and manufacturer.

Symptoms

Glow plug or engine warning light on the dash
Hard starting in cold weather
Extra white smoke or rough running for the first minute after a cold start
Longer cranking time when cold
Increased diesel knock until the engine warms up
Engine running normally once warm, with the fault stored

Possible causes

One or more failed glow plugs on circuit B (open circuit or high resistance)likely
Corroded, loose or damaged wiring or connectors between the glow plug control module and the plugslikely
Faulty glow plug control module or relay, or its driver stagepossible
Poor power or earth supply to the glow plug module, or a blown fusepossible
Short to earth or to supply in the circuit B wiringpossible
Fault in the engine control unit output or communication with the glow plug modulerare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature, battery voltage and whether other glow plug or starting codes are present
Check the relevant fuses and the battery condition and charging voltage, as low voltage can upset glow plug monitoring
Visually inspect the glow plug wiring, connectors and the control module plug for corrosion, heat damage, chafing or looseness
Check the model-specific wiring diagram to identify which glow plugs belong to circuit B
Measure the resistance of each glow plug on the circuit against the manufacturer's specification, with the supply disconnected
Check the power and earth feeds to the glow plug module and the relay operation
Use a scan tool that can activate the glow plugs and monitor current draw or module feedback, comparing against the model's specification
Test the circuit wiring for continuity and for shorts to earth or supply

How to fix

Replace any glow plugs found open circuit or out of specification, following the correct torque and removal procedure for the engine
Repair or replace damaged wiring, terminals or connectors, and clean corroded contacts
Replace the glow plug control module or relay if it fails testing
Restore faulty power or earth supplies and replace blown fuses once the cause is found
Clear the code after repair and confirm it does not return on a cold start test

Can I keep driving?

Low severity

The car can usually be driven, but cold starting may be poor and emissions higher on a cold engine. Book it in soon, especially before cold weather, and avoid repeated long cranking.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.