Can I drive with P0380?

Once started, the engine runs normally — the fault only affects cold starting and cold-running smoothness. Fix it before cold weather.

Replace one glow plug or all?

On a high-mileage engine, replace as a set: the others are the same age, and labor often dominates the job.

Why white smoke when cold?

Cold cylinders without pre-heat don't fully burn the injected diesel; the unburned fuel exits as white smoke until temperatures rise.

Engine (Diesel) · Generic OBD-II

P0380 — Glow Plug/Heater Circuit "A" Malfunction

The diesel glow-plug circuit has an electrical fault — expect hard cold starts and white smoke until the pre-heat system is healthy again.

By iCarsoft Engineering Team Updated July 2, 2026 Checked against SAE J2012

Quick reference

Severity

Medium

Safe to drive

Caution

System

Engine (Diesel)

Code type

Generic

Repair level

DIY-Moderate

Typical cost

$50–$600

Glow plugs are wear items. On a high-mileage diesel, testing all of them (not just one) is the professional move.

What triggers it

Common causes, most likely first

Failed glow plug(s)

Plugs burn out with age; one open plug can set the circuit code.

Very common

Glow plug relay / control module

The controller that times and feeds the plugs fails or sticks.

Very common

Blown fuse / fusible link

The high-current feed to the glow circuit is protected — and vulnerable.

Common

Wiring or bus-bar corrosion

High-amp connections corrode, especially on older engines.

Occasional

How it shows up

Symptoms you'll notice

Hard starting when cold — long cranking, worse the colder it gets.
White smoke at cold start — unburned diesel from cold cylinders.
Glow plug lamp abnormal — stays on or flashes.
Rough running until warm — smooths out as the engine heats.

In warm weather a diesel may start fine despite P0380 — don't let easy summer starts hide a dead pre-heat system before winter.

How to pinpoint it

Diagnostic steps

Check the glow circuit fuse/fusible link

The 30-second first check on any glow fault.Tool: visual + multimeter

Measure each glow plug's resistance

Typically under ~2 Ω each; open or high readings identify dead plugs.Tool: multimeter

Verify relay/module output

Confirm battery voltage reaches the plugs during the pre-glow window.Tool: multimeter

Command a glow cycle and watch amp draw

Total current divided by per-plug draw counts how many plugs actually work.Tool: bidirectional test + amp clamp

What the fix costs

Repair & cost

Glow plug (each)

$20–60

Often replaced as a set

Relay / control module

$80–300

Common failure point

Wiring repair

$50–200

High-current connections

Estimates are indicative and vary by region, vehicle and parts choice. Confirm the actual cause with live data before buying parts.

Diagnose it yourself

The right iCarsoft tool for P0380

iCarsoft CR Pro S

CR Pro S commands the glow cycle on demand and reads glow-plug feedback on supported diesels — pinpointing dead plugs and a lazy controller without pulling the valve cover in the cold.

Full-system scanLive data graphingBi-directional testsService resets

View iCarsoft CR Pro S Compare tools

Coming soon

Analyze your exact vehicle with the AI Co-Pilot

Enter your make, model and what you're seeing — the iCarsoft AI assistant will rank the likely causes for your car and suggest the next test.

Try the AI Co-Pilot

Quick answers

P0380 FAQ

Can I drive with P0380?: Once started, the engine runs normally — the fault only affects cold starting and cold-running smoothness. Fix it before cold weather.
Replace one glow plug or all?: On a high-mileage engine, replace as a set: the others are the same age, and labor often dominates the job.
Why white smoke when cold?: Cold cylinders without pre-heat don't fully burn the injected diesel; the unburned fuel exits as white smoke until temperatures rise.

P0380 — Glow Plug/Heater Circuit "A" Malfunction