P0382

Code

LAND ROVER P — Powertrain

Glow plug / heater circuit B

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 23 EN: 28 RU: 28

AI status

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Page language: EN

Causes

Open or high-resistance wiring in glow plug circuit B (broken wire, corroded connector)
Short to ground or short to battery in circuit B
Faulty glow plug(s) on circuit B (high resistance or shorted)
Failed glow plug relay, fuse, or heater control module
Poor battery or charging system voltage during preheat
Faulty ECM / glow plug driver output (less common)

Symptoms

MIL (check engine light) illuminated
Poor or slow cold starting, especially in cold ambient temperatures
Longer cranking or extended cranking time
White or increased exhaust smoke during cold start
Glow plug or preheat warning lamp illuminated (if fitted)
Intermittent starting issues or rough idle until engine warms

What to check

Retrieve DTC(s) and freeze-frame data with an OBD-II scanner; note related codes
Confirm battery voltage and state of charge (battery should be fully charged)
Visual inspection of glow plug wiring, connectors, relays, fuses, and grounds for corrosion, damage or looseness
Check for additional related codes (other glow plug circuit codes, low battery voltage codes)
Backprobe glow plug connector(s) and relay/driver connector while commanding preheat with a scan tool
Measure glow plug resistance (cold) and compare between cylinders

Signal parameters

Glow plug control output voltage: approximately battery voltage (~11–14 V) at the relay/driver output when preheat is commanded
Glow plug resistance (cold): typically low — commonly 0.2–3 Ω per plug depending on design; a much higher or infinite reading indicates open/failed plug
Aggregate current draw: when multiple plugs energized, expect significant current; individual plug current varies by design (measure with clamp meter)
No voltage present at circuit B when commanded indicates open circuit, blown fuse, bad relay or driver
Very high current or short to battery indicates short circuit or internal short in one or more plugs

Diagnostic algorithm

Read and record all fault codes and freeze-frame data. Clear code and attempt to re-run to confirm reproducibility.
Verify battery voltage and charging system health. Recharge or replace battery if low before further testing.
Visually inspect glow plug harness, connectors, relay, fuse and grounds for corrosion, overheating or damaged insulation. Repair obvious damage.
Identify which cylinders belong to circuit B (refer to vehicle service manual/wiring diagrams).
With ignition OFF, disconnect glow plug connector(s) for circuit B and measure resistance of each glow plug to engine ground. Compare readings across plugs; replace any with open or significantly higher resistance.
Check continuity of wiring from glow plug connector back to relay/driver and from relay to fuse/ignition feed; repair broken wires or poor grounds.
With a scan tool, command glow plug preheat and backprobe the driver output for circuit B. Verify voltage present when commanded. If no voltage but relay coil energized, test relay and fuse.
Measure current draw for circuit B while energized (use clamp meter on supply lead) to detect short/high current in one or more plugs.
If a suspect glow plug is identified, swap it with a plug on another circuit (if possible) and see if the fault follows the plug or remains on circuit B.
If wiring, plugs, relay and fuse are good but no proper driver output is present, test/replace the glow plug driver module or associated relay. If driver replacement does not resolve, consider ECM diagnosis by a qualified technician.
Safety note: glow plugs and engine components can be hot; isolate battery when performing live repairs on wiring and take care to avoid shorts.

Likely causes

Corroded or disconnected injector/glow plug connector on one or more cylinders in circuit B
One or more glow plugs on circuit B internally failed (open or short)
Faulty glow plug relay or control module supplying circuit B
Damaged wiring harness where it routes near heat or moving components
Low battery voltage causing abnormal readings during preheat

Fault status

⚠️ Status

ECM detected malfunction in Glow Plug/Heater Circuit B. Preheat function for circuit B may be disabled or degraded; this will affect cold starting performance and may trigger MIL. Further inspection required to locate open, short, or driver fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

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P0382 — Glow plug / heater circuit B