By iCarsoft Official Store Technical Team, Automotive Diagnostics Editors · Updated September 8, 2026 · Technical sources checked
Quick Answer
The P0382 code means glow plug/heater circuit b. It does not prove circuit B identifies cylinder 2 or bank 2, or that every glow plug has failed. Save the scan, identify the exact architecture, and test the physical and electrical paths before selecting a repair.
What Does the P0382 Code Mean?
P0382 means Glow Plug/Heater Circuit B. It names a monitored result, not a guaranteed failed part. The reporting module, suffix and companion faults determine the relevant test branch.
A diesel preheat/heater circuit fault; B is an OEM circuit designation, not a reliable cylinder or bank map. Glow-plug type and controller voltage vary.
A preheat request and delivered heating are different evidence. Supported status shows the command; current and supply tests assess the load. Neither the lamp nor P0382 identifies which plug should be removed.
Snap-on's manufacturer code catalog confirms circuit B. Niterra/NGK explains cold-start/after-glow function and that excessive voltage from a controller can damage glow plugs; this does not establish any vehicle's P0382 threshold.
Niterra/NGK discusses after-glow and controller-overvoltage damage. This background supplies no P0382 threshold, fixed heating duration or vehicle-specific B-circuit map. Those decisions require the engine’s service information.
Separate P0382 from adjacent fault families
| Code | General description | Key distinction |
|---|---|---|
| P0382 | Glow plug/heater circuit B | B identifies a circuit group defined by the manufacturer, not an automatic cylinder or bank number. |
| P0380 | Glow plug/heater circuit A | A different circuit designation; its physical grouping must also come from the engine diagram. |
| P0670 | Glow plug control module control circuit/open | A control-module circuit classification, distinct from assigning the general B heater circuit. |
| P0672 | Cylinder 2 glow plug circuit/open | This label explicitly names cylinder 2; P0382 does not make that same assignment. |
Record the complete P0382 description. The suffix, reporting module and companion faults can change the diagnostic path. Use the manufacturer's full wording and test procedure for the exact vehicle.
P0382 Symptoms and Likely Causes
P0382 symptoms depend on fault status and the fallback strategy. Record what the driver and modules reported. A symptom list is not a parts list.
Record ambient conditions, engine temperature and cranking behavior. A starting problem that improves when warm can guide the preheat investigation, but also requires consideration of unrelated starting and combustion faults.
Note how long the roughness lasts and whether it occurs only after a cold start. Smoke color and uneven running are observations, not proof that a particular heater element failed.
Save the actual warning and full diagnostic text. Dashboard lamp duration does not independently measure heater current, so a normal-looking lamp cannot clear the circuit from the investigation.
A warm engine may start without a noticeable complaint even though a circuit fault is stored. Do not assume that one easy restart exercised the conditions under which the preheat monitor detected P0382.
Practical cause-checking order
- Connection evidence: Loose high-current connections, corrosion or damaged harness insulation can interrupt the identified B circuit. Inspect the documented connections and evidence of heating before selecting individual glow plugs for replacement.
- Electrical path: A fuse, supply, ground or load-path defect can prevent commanded heating. Separate the controller’s power circuit from its command and feedback wiring; one intact connection does not establish that the entire path is healthy.
- Supporting condition: An implausible temperature input or a shared supply problem may affect the preheat conditions. Follow companion faults when present rather than assuming that the observed command is appropriate for the actual cold engine.
- Component evidence: A heater element may fail, but its designation and test method depend on the engine. Check the installed plug type and circuit mapping before transferring a resistance expectation from another diesel design.
- Final decision branch: A controller or relay fault is considered after its supplies, connected loads and control evidence are established. Incorrect replacement parts or excessive controller voltage can damage the next heater instead of solving the original concern.
Did P0382 appear after recent glow-plug, preheat-controller, battery or engine-harness service? Recheck the documented connections, parts and setup steps affected by that work. Record battery and software history; a post-repair code does not prove the new part is defective.
How Serious Is P0382, and Can You Drive?
Arrange diagnosis before the next difficult cold start. Further use depends on normal running, intact electrical wiring and the vehicle manual; stop repeated cranking when components overheat.
Record temperature, load, speed, start state and recent service. Do not reproduce a severe symptom on public roads; another warning can make the situation more urgent.
Stop and arrange a tow if wiring smokes, cables or the battery overheat, a heater remains energized unexpectedly, or the engine cannot run safely.
Glow and intake-heater circuits can carry substantial current. Isolate them by the service procedure before handling connections. Do not use starting fluid around an active heater, and never connect battery voltage directly to a plug whose design and test requirements are unknown.
How to Diagnose P0382 in the Right Order
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Save the cold-start record before clearing
Save P0382 with its status, available freeze frame and all preheat, battery or temperature-related faults. Record whether starting was cold or warm, the ambient conditions and the exact cranking symptom. Avoid repeated attempts that overheat the starter or cables; secure the evidence without creating another electrical problem.
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Identify the heater type and B-circuit map
Identify the engine, installed heater type and manufacturer’s meaning of circuit B. Map the controller, relay if fitted, supply protection and heater group. Do not substitute a cylinder-2 test solely because B is the second letter, or apply an intake-grid-heater method to an individual glow-plug system.
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Inspect the circuit with power safely isolated
Follow the specified isolation procedure, then inspect accessible fuses, controller connections and the relevant loom. Look for loose terminals, melted insulation and recent-work damage. A fuse that has failed is evidence of a circuit problem; determine why before simply installing another fuse or bridging its protection.
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Prove supply and ground under the permitted load
Use the approved load or voltage-drop procedure to check the power and ground paths. Observe the system’s isolation and test-state requirements. High-current terminal integrity matters even when an unloaded meter reading appears normal; avoid improvised connections that bypass the controller or create an uncontrolled heater load.
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Compare commanded heating with measured response
Compare supported preheat command and current information with the specified physical tests for the actual plugs or heater. Use the engine’s resistance, current and temperature criteria. Do not apply direct battery power to an unknown-voltage element or condemn all plugs because one controller-level measurement is outside specification.
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Verify the repair under actual preheat conditions
Repair the proven connection, supply, heater or controller branch and verify correct replacement parts. Confirm heating shuts off or changes state as the design requires. Recheck the starting complaint and monitor under suitable cold/preheat conditions, preserving the results; an easy warm start alone is not a completed verification.
Specifications are vehicle-specific. There is no universal voltage, resistance, current, pressure, waveform, timing, temperature, percentage, learned value or drive cycle for P0382. Test state, connector location and system design change what a valid value means. Use only specifications for the exact VIN and do not transfer the OEM example in this article to another application.
P0382 Repairs and Typical Costs
The correct P0382 repair follows the failed test. Wiring, a physical repair, a proven component, software and controller work are different outcomes. Do not replace an assembly from the generic code alone.
After installation, recheck connector seating, harness clearance, fluid or mechanical setup and every required learn. Match replacement heaters to the engine and controller. Repeated plug failure requires checking the supply and control strategy. Visually similar plugs need not share voltage ratings or operating characteristics.
| Possible path | Current US estimate |
|---|---|
| Restore a confirmed B-circuit connector or harness defect | VIN-specific quote |
| Repair the proven protected supply or ground path | VIN-specific quote |
| Replace only heater elements that fail the specified test | VIN-specific quote |
| Repair or replace a verified controller and confirm correct heater matching | VIN-specific quote |
There is no single national P0382 repair price because these rows are alternative outcomes. Ask for an itemized estimate showing diagnostic time, parts, labor, fluids, service-information access and verification. Location, taxes, related damage and warranty eligibility change the total. Do not add the rows together or authorize an assembly without the supporting failed test.
Using iCarsoft CR Eagle P for P0382
On a supported vehicle, iCarsoft CR Eagle P can retrieve accessible module faults, save available freeze frame, display ECU-provided live data and create a diagnostic report. For P0382, preserve the original evidence and compare related modules before clearing an erasable record.
Preserve the glow plug circuit B evidence
iCarsoft CR Eagle P
Review supported codes and relevant live data together. Confirm the exact VIN, controller access, PIDs and any requested active test with iCarsoft before purchase; generic product capabilities do not guarantee a P0382-specific function.
Check current CR Eagle P price and availabilityCheck CR Eagle P compatibility by VINThe official product page describes full-system diagnostics, available freeze frame and live data, and supported bidirectional tests and ECU coding; availability varies with the vehicle, ECU and software. Confirm the requested function by VIN before purchase. Follow OEM prerequisites and stop for abnormal operation.
Know the measurement boundary. The scanner reports information supplied by the vehicle. It does not directly prove terminal tension, circuit load capacity, leakage, pressure, temperature, mechanical travel or internal condition in the glow plug circuit B. It also cannot replace the specified low-resistance or current-test equipment and approved heater-system wiring information when the OEM procedure requires them. Interpret commanded and reported values alongside measured evidence.
Verify the P0382 Repair
After repair, verify connectors, harness clearance, setup and controller supply. Save post-repair findings, then clear only erasable records through the approved procedure. Battery disconnection is not a repair.
Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the glow plug circuit B, and check current and pending faults in related modules. One clean start or idle period does not prove that every conditional monitor has completed.
If P0382 returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Keep mechanical repair, monitor completion, readiness and local inspection eligibility as separate outcomes.
A permanent P0382 can remain immediately after a successful repair. If the vehicle stores it as a permanent DTC, a scan tool or battery disconnect cannot erase it. Once current and pending faults are absent, the OBD system removes the permanent record only after the applicable monitor reruns and passes.
Related Glow Plug Circuit B Code Guides
P0382 Frequently Asked Questions
Does P0382 mean the named component is bad?
No. P0382 describes glow plug/heater circuit b, not a confirmed part. It also does not prove circuit B identifies cylinder 2 or bank 2, or that every glow plug has failed. Test accessible wiring, supplies, grounds and supporting physical conditions, then follow the exact monitor tree. Replace a component only when its branch fails or an applicable OEM action specifically supports it.
What should I check first for P0382?
Save every module's codes and freeze frame before clearing. Confirm the full definition, suffix and VIN architecture. Then inspect recent glow-plug, preheat-controller, battery or engine-harness service, connectors and shared supplies. Those facts determine whether the next test needs the specified low-resistance or current-test equipment and approved heater-system wiring information or a manufacturer-specific functional procedure.
Can I drive with the P0382 code?
Arrange diagnosis before the next difficult cold start. Further use depends on normal running, intact electrical wiring and the vehicle manual; stop repeated cranking when components overheat.
Why did P0382 return after a part was replaced?
A new plug can leave connector, feed, circuit-mapping or controller faults unresolved. Confirm what failed before replacement and retest under required temperature conditions. A warm restart does not establish correct B-circuit operation.
What should a P0382 repair estimate include?
A VIN-specific estimate is required because diagnosis may lead to wiring, a supporting physical repair, a verified component, software or a controller. Ask which failed test supports the quote and whether diagnosis, taxes, setup and post-repair verification are included.
Can CR Eagle P diagnose and clear P0382?
On a supported vehicle, CR Eagle P can organize available faults, freeze frame, live data and reports, and can clear erasable records after repair. Confirm exact ECU coverage. It cannot force-clear a permanent DTC or replace physical measurements for the glow plug circuit B.
The iCarsoft Official Store Technical Team maintains the store's fault-code library. This guide organizes published manufacturer evidence and verified product information; it does not document a hands-on test of a particular vehicle or claim an individual engineer's review.
Technical and cost references
- Diagnostic Trouble Codes (DTC) List. Generic DTC definition only; not vehicle-specific test limits or repair verdict.
- Niterra/NGK: You asked Google – Part 3: Glow plugs. Glow-plug purpose, after-glow and failure risks including controller overvoltage; not P0382-specific monitor values.
- California Bureau of Automotive Repair — On-Board Diagnostic Test Reference. Permanent DTCs are removed by the vehicle after applicable verification, not by a scan-tool erase command.
Product information: Official iCarsoft CR Eagle P page.
Editorial note: General diagnostic education, not a substitute for the owner's manual, current VIN-specific service information or professional inspection. Test limits, procedures, coverage and costs vary. Related articles provide context; apply only the specifications and repair procedures that match the vehicle. No universal failure rate, repair price or outcome is implied.
