Ignition and pre-heatingGeneric OBD-II codeUrgency: Garage soon
Code P0380: glow plug circuit fault
P0380 means: glow plug (heater) circuit "A": malfunction.[1][2][3] The control unit has detected a fault in the control circuit of glow plug heater "A", also known as heater plugs or glow plugs. It mainly affects diesel engines: these plugs heat the combustion chambers before starting so that the mixture of diesel and air can ignite by compression with the engine cold.[1][4]
What code P0380 means
The control unit has detected a fault in the control circuit of glow plug heater "A", also known as heater plugs or glow plugs. It mainly affects diesel engines: these plugs heat the combustion chambers before starting so that the mixture of diesel and air can ignite by compression with the engine cold.[1][4]
The code indicates there is a problem in the circuit, but not which part is failing: it could be the glow plugs themselves, the relay, the fuse, the wiring, the earths or the control unit. That is why the circuit must be checked step by step before replacing anything.[1][2][3]
It is a generic OBD-II code (it starts with P0), so it means the same thing on any make; what changes from one engine to another is the most likely cause.[5]
Original definition (SAE J2012): Glow Plug/Heater Circuit "A" Malfunction[1][2][3]
Codes from the same family
They indicate the same problem in a specific cylinder, bank or sensor. Causes, symptoms and diagnosis are those on this page.
Causes of P0380 and its family
From most to least likely, according to the sources.
- 1Faulty glow plugs (heaters).[1][2][3]
- 2Faulty glow plug relay.[1][2]
- 3Blown fuse in the pre-heating circuit.[1][2]
- 4Wiring and connections in poor condition: broken wires, corroded or loose connectors.[1][2][8]
- 5Faulty glow plug control unit (module).[1][2][8]
- 6Faulty, dirty or loose earth wire or connection.[1][8]
- 7Faulty temperature sensor in the pre-heating system.[1]
Symptoms
- Hard starting from cold, with a longer cranking time than normal; in low temperatures the car may refuse to start.[1][2][4]Hard to start: faults that cause it
- The glow plug warning light takes longer than normal to go out, flashes, stays on or a message appears on the on-board computer.[2][4]Flashing glow plug light: faults that cause it
- Engine warning light on, although Klavkarr warns that this code can be stored without any warning light coming on.[1][2][3][4][8]Engine warning light: faults that cause it
- Unstable idle and an engine that misfires for a few seconds after a cold start.[1][4]Vibrations: faults that cause it
- White or bluish smoke from the exhaust and strong smells on a cold start, from poor combustion in the first few seconds.[1][4]
- Loss of power, especially with a cold engine.[1]Less power: faults that cause it
How to diagnose P0380
In order: from the most likely and cheapest to check to the most expensive.
- 1Start with the simplest things: check the pre-heating circuit fuse and the relay.[1][2]
- 2Check the wiring, connectors and earths: broken wires, rust or loose terminals. Gently wiggle the wires and connectors to detect intermittent faults, and clean and tighten the earth connections.[1][2][8]
- 3With a multimeter, check that the glow plug connector is receiving power and earth, and measure the voltage at the glow plug terminals during pre-heating. Advanced diagnostic equipment also lets you see the functions of the pre-heating circuit.[2][3][8]
- 4Measure each glow plug separately: disconnect the connector or the power cable and measure its resistance with a multimeter (this can be done without removing them). A burnt-out plug reads open circuit. Compare with the manufacturer's value: Autodoc Club normally quotes between 0.6 and 2 Ω and Klavkarr about 0.7 Ω on a 2.0 HDi engine, although many multimeters are not accurate with such low values. Replace only the ones that deviate.[1][3]
- 5Diagnose the pre-heating control unit and replace it only if the glow plugs, relay, fuses and wiring are all fine.[1][3][8]
Can I keep driving with P0380?
Garage soon
Autodoc Club says you can normally keep driving with a warm engine, but that the fault should be resolved as soon as possible. Diariomotor explains why: with faulty heater plugs the starter motor and battery are put under extra strain and the car can leave you stranded unable to start, especially if it is cold.[1][4]
Documented faults related to P0380
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityOccasionalFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityOccasionalFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityOccasionalFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityOccasionalFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityOccasionalFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
- Critical severityOccasionalFrequency: OccasionalAudi A4 B9Risk of short circuit and fire due to moisture in electrical componentsAudi recalled A4 B9 units built between May 2017 and March 2020 because moisture can seep into an electrical component and cause a short circuit, with a risk of the vehicle catching fire.Repair: €0
12 V battery: the most serious faults by engine and car
- Medium severityCommonFrequency: Common2.0 and 2.5 HybridThe 12 V battery goes flat if the car sits unused for several daysYes, it is a common complaint: the 12 V battery can go flat after just a few days without using the car, because of the standby drain from the electronics (multimedia, telematics, keyless entry). With the 12 V battery very low, the hybrid system can lock itself into a safe mode.
- Medium severityOccasionalFrequency: OccasionalE-Tech Híbrido12 V battery going flat or needing early replacementSeveral Clio, Arkana and Austral owners with the E-Tech engine document premature replacement of the 12 V auxiliary battery, in one case twice in the first year. It is not the most widespread fault of the system, but it appears repeatedly across different models.
- Medium severityOccasionalFrequency: Occasional1.5 Hybrid12 V battery going flat while parkedYes: on the hybrid Yaris and Yaris Cross, the 12 V battery can go flat within a few days while parked because of the residual draw of modules such as eCall or keyless entry. It is fixed with a software update or, if the battery is already damaged, by replacing it.
- High severityCommonFrequency: CommonHyundai Ioniq 5Faulty ICCU: 12 V battery drain and loss of drive powerThe Integrated Charging Control Unit (ICCU) can fail on the Ioniq 5: it drains the 12 V battery, may refuse to charge and, in the most serious cases, cause the car to lose power or not go into drive mode. Hyundai has replaced this part and updated its software on units built between January and February 2023.
- High severityOccasionalFrequency: OccasionalFord Galaxy IIIAcid leak from the 12 V battery (campaign 18P11)According to the fiches-auto.fr page, campaign 18P11 (August 2019) covers Galaxies built between February 2014 and February 2019 over a risk of battery acid leaking, which can worsen over time.
Alternator and starter motor: the most serious faults by engine and car
- High severityOccasionalFrequency: Occasional2.2 JTDm Multijet IIAlternator cable touching the exhaust gas recirculation pipe (fire risk)An Alfa Romeo campaign covers diesel Stelvio built between 18 January 2017 and 18 September 2018: an alternator cable may rub against the exhaust gas recirculation pipe and cause a short circuit, with a fire risk in the worst case.
- Medium severityOccasionalFrequency: Occasional1.7 CDTIPremature alternator wearThe Hitachi-brand alternator fitted at the factory to the 1.7 CDTI tends to wear out sooner than expected, according to a German buying guide on the Opel Astra H, with typical replacements at around 140,000 km; there are similar accounts on the Opel Meriva with this engine.
- High severityCommonFrequency: CommonFord Focus IIAlternator fault with false battery, ESP and power steering warningsThe alternator is the most repeated electrical fault of the Focus II across all engines: an unstable charge lights the battery and ESP warning lights for no real reason and, in the most pronounced cases, an occasional loss of power steering assistance may be noticed.Appears at around 60,000 km
- Critical severityOccasionalFrequency: OccasionalAlfa Romeo JuniorRisk of electric arcing at the 48 V starter-generator terminal on the hybrid JuniorYes: a March 2026 Safety Gate alert (campaign F60F) covers Junior MHEVs built between 27 November 2023 and 18 December 2025. The clearance between the particulate filter pipe and the 48 V starter-generator terminal cover is under 10 mm and, in damp conditions, there could be electric arcing and fire.
Frequently asked questions
Can I drive with code P0380?
Normally yes, especially with a warm engine, but it should be repaired as soon as possible: when cold the car may be hard to start or may not start at all, and every forced start puts extra strain on the starter motor and the battery.[1][4]
Does code P0380 mean the glow plugs are broken?
Not necessarily. It indicates a fault in the pre-heating circuit without specifying the cause: it could be the glow plugs, but also the relay, the fuse, the wiring, the earths or the control unit. That is why each glow plug is measured and the fuse, relay and power supply are checked before replacing any part.[1][2][3]
Does code P0380 affect petrol cars?
In principle no: Autodoc Club states that it mainly affects diesel vehicles, and Diariomotor explains that glow plugs are essential components for starting diesel engines.[1][4]
How do you test glow plugs?
The connector or power cable of each glow plug is disconnected and its resistance is measured with a multimeter; a burnt-out plug reads open circuit. The voltage at its terminals is also measured during pre-heating to see whether the circuit is powering them.[1][3]
Can a pre-heating fault make me fail the MOT?
Diariomotor warns that the glow plug warning light or the engine warning light being on could mean a fail in the ITV (the Spanish roadworthiness inspection, equivalent to the MOT), even an unfavourable result. It is best to resolve the fault before taking the car in.[4]
Will I pass the MOT with code P0380?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[9]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- 1.Código OBD2 P0380: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- 2.P0380 OBD Error Code: Problem & SolutionsPartsAvatar · Technical documentation · published 13 March 2023 · consulted 2 October 2026
- 3.P0380 / P0670 fault codes: glow plug diagnosis and repairKlavkarr · Technical documentation · consulted 2 October 2026
- 4.Cómo detectar que los calentadores de un coche diésel están en mal estadoDiariomotor · Motoring press · published 16 January 2020 · consulted 2 October 2026 · in Spanish
- 5.On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- 6.Código OBD2 P0381: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- 7.P0381 – Glow plug warning lamp -circuit malfunctionTroubleCodes.net (BAT Auto) · Technical documentation · consulted 4 October 2026
- 8.P0380 9-5 (9600) 2010, sistema de gestión del motor EDC 16Saab WIS Online (Saab Workshop Information System) · Technical documentation · consulted 2 October 2026
- 9.Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish