What it means
A general electrical fault on glow-plug heater circuit B — typically the second bank of glow plugs on an inline-6 or V-engine.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Glow plug heater circuit B powers the glow plugs assigned to that circuit, which may serve a separate group of cylinders depending on the engine layout. The control module monitors circuit B for electrical faults and sets P0382 when its response is abnormal; the code does not by itself identify a specific failed plug or whether the fault is open or shorted.
Common causes
Most likely first.
- One or more glow plugs in circuit B failed
- Open, shorted, or damaged glow-plug wiring
- Loose or corroded connector
- Fault in the glow-plug control module or relay
Symptoms
- Glow plug warning light on (often orange coil symbol)
- Hard cold start or no start in cold weather
- White smoke from exhaust during warm-up
How to diagnose it
- Record freeze-frame data and check commanded glow plug operation and circuit B status during a cold start.
- Identify which plugs the vehicle assigns to circuit B from its service information, then inspect their wiring and connectors.
- Check the circuit B glow plugs for open or other electrical faults using the manufacturer's procedure.
- Test circuit B power delivery and its relay or control output while glow plug operation is commanded.
- If the plugs and wiring pass, test the glow plug control module and circuit B inputs against the manufacturer's specification.
Common fixes
- Clean and secure loose or corroded circuit B connections.
- Repair damaged circuit B wiring or connectors.
- Replace failed glow plug or plugs assigned to circuit B.
- Replace a faulty relay or glow plug control module if testing confirms it.
Can I keep driving?
A circuit B fault can reduce cold-start heating, leading to difficult starting and white smoke during warm-up. Avoid prolonged cranking in cold weather, and drive gently if the engine starts and runs normally.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.