Ignition and pre-heatingGeneric OBD-II codeUrgency: Garage soon
Code P0683: ECU to glow plug module communication
P0683 means: glow plug (heater) control module to ECU (PCM) communication circuit.[1][2] The ECU (PCM) has detected a communication fault between itself and the glow plug control module, the unit that powers the heaters of a diesel engine. TroubleCodes.net explains that the ECU needs to know what is happening in that circuit at all times in order to manage the fuel and the engine's other strategies; Autodoc Club sums it up as a communication or electrical supply problem with the glow plug control unit. It only occurs on diesel engines.[1][2]
What code P0683 means
The ECU (PCM) has detected a communication fault between itself and the glow plug control module, the unit that powers the heaters of a diesel engine. TroubleCodes.net explains that the ECU needs to know what is happening in that circuit at all times in order to manage the fuel and the engine's other strategies; Autodoc Club sums it up as a communication or electrical supply problem with the glow plug control unit. It only occurs on diesel engines.[1][2]
According to BorgWarner, current systems use a module with a microcontroller that defines the timing, intensity and duration of the current the glow plugs receive and that maintains constant communication with the engine ECU; older systems used a relay that worked mainly as a switch.[3]
The code points to the communication circuit, not to a specific part. TroubleCodes.net warns that a basic reader shows the code, but not the bidirectional tests that confirm which part has really failed and not just which circuit raised the warning. Klavkarr also distinguishes P0670, which points to the glow plug control module, from P0380, which points to heater circuit "A".[2][4]
It is a generic OBD-II code (it starts with P0), so it means the same on any make; what changes from one engine to another is the most likely cause.[5]
Original definition (SAE J2012): Glow Plug Control Module to PCM Communication Circuit[1][2]
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.
- P0683Glow plug (heater) control module to ECU (PCM) communication circuit.
- P0684Glow plug control module to ECU (PCM) communication circuit: range or performance.[6]
Causes of P0683 and its family
From most to least likely, according to the sources.
- 1Faulty glow plug control module. TroubleCodes.net notes that these modules fail relatively often because on many cars they are close to hot parts of the engine or exhaust.[1][2]
- 2Damaged circuit wiring and connectors: damaged, burnt, short-circuited, disconnected or corroded.[1][2][6]
- 3Blown fuse, or high-current fuse, in the glow plug circuit.[1][2][6]
- 4Low battery voltage or problems with the car's supply voltage.[1][2][6]
- 5Damaged earth cable or connection.[1]
- 6CAN bus communication fault, which Autodoc Club includes among the causes.[1]
- 7One or more faulty glow plugs.[1][2][6]
- 8Faulty coolant temperature sensor or other engine sensors, and replacement glow plug modules of doubtful quality, according to TroubleCodes.net.[2][6]
- 9Faulty ECU, or one with a failed internal glow plug driver.[2][6]
Symptoms
- Difficulty starting from cold, with longer cranking than normal. TroubleCodes.net, in its P0684 entry, even states that the engine may not start from cold.[1][6]Hard to start: faults that cause it
- White, grey or even dense black smoke from the exhaust on a cold start.[1][6]
- Rough idle after a cold start.[1][6]Vibrations: faults that cause it
- Engine warning light on.[1]Engine warning light: faults that cause it
- Noticeable loss of power with the engine cold.[1]Less power: faults that cause it
How to diagnose P0683
In order: from the most likely and cheapest to check to the most expensive.
- 1Check the battery and the supply voltage: both Autodoc Club and TroubleCodes.net include low or unstable voltage among the causes.[1][2][6]
- 2Check the fuse (and the high-current fuse) of the glow plug circuit and the earth connections.[1][2]
- 3Inspect the module's wiring and connectors: breaks, burns, corrosion or loose terminals. Clean and secure the circuit's connections.[1][2]
- 4Connect a diagnostic tool that reads all the car's modules and allows bidirectional tests, to see whether the module responds. Autodoc Club also cites diagnosing CAN bus communication errors.[1][2]
- 5Measure the resistance of each glow plug and the voltage at its terminals during pre-heating: Autodoc Club recommends replacing faulty glow plugs after measuring their resistance, and Klavkarr uses the voltage measurement to find out whether the module is powering the glow plugs.[1][4]
- 6Replace the module only after diagnosing it and leave the ECU until last: TroubleCodes.net lists it among the causes, along with its internal glow plug driver.[1][2]
Can I keep driving with P0683?
Garage soon
Autodoc Club says you can drive in the short term, but that you should expect cold-starting problems, and it recommends a prompt repair because the problem may get worse. TroubleCodes.net, in its P0684 entry, warns that the engine may not start from cold and that prolonged cranking can damage the battery and starter motor; in its P0683 entry it points out that glow plugs are not needed to start a hot or even warm engine.[1][2][6]
Parts related to code P0683
The parts that most often cause this code. The code points to the circuit, not always the part: diagnose before you buy.
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Documented faults related to P0683
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 severityFrequency: 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.
- Critical severityFrequency: Occasional1.6 GDi híbrido (Kappa)Main relay of the power relay assembly (overheating and fire risk)Yes, on the first units: Hyundai and Kia recalled 2016–2018 Ioniq and Niro hybrids and plug-in hybrids because the main relay that connects the high-voltage battery could come loose, overheat and, in the worst case, cause a fire.
- Critical severityFrequency: Occasional1.6 GDi híbrido (Kappa)Clutch hydraulic actuator (HCA): leak or moisture with risk of short circuit and fireYes, this is the most documented hybrid system fault: the hydraulic actuator that engages the combustion engine with the hybrid assembly has had two recalls (2018 for a leak on the Niro and 2025 for moisture in its electronic board on the Niro, Ceed and XCeed PHEV), with a risk of short circuit and fire.
- High severityFrequency: 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.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: 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.
Control units and comfort electronics (BSI, SAM...): the most serious faults by engine and car
- High severityFrequency: CommonPeugeot 408Electronic faults with the doors, boot and screen (suspected BSI control unit)In 2025 Peugeot recalled around 60,000 2023-2024 Peugeot 308 and 408 cars (code MUV) over a software fault in the door control unit that can cause unintended opening or closing and disable the anti-trap protection on the windows; 408 owners also describe a power boot lid that will not open or close and a screen that goes black.
- High severityFrequency: CommonRenault Laguna IIMultiplex electrical system and hands-free card faultsThe Laguna II had a reputation problem because of faults in its multiplexed electrical network: the hands-free card, the card reader and the ABS, ESP and handbrake warning lights came on erratically, especially in the early years of production (2001-2003).
- Critical severityFrequency: OccasionalMazda MX-5 IVDC/DC converter control unit fault with risk of short circuit and fireA 2018 Safety Gate alert covers MX-5 ND models built between August 2014 and April 2017: the DC converter control unit could fail, cause a short circuit and damage the converter, with a risk of fire. It is a precautionary recall; check the chassis number at the official service centre.
- Medium severityFrequency: Very frequentFiat StiloElectrical and electronic faults in the multiplex systemThe Stilo has had a reputation for widespread electrical faults since its launch: poor contacts in the multiplex wiring, an instrument cluster that switches off and sensors that disconnect, sometimes while the car is running.
12 V battery: the most serious faults by engine and car
- High severityFrequency: CommonHyundai-Kia E-GMP (Ioniq 5, Ioniq 6, EV6)Faulty ICCU: 12 V battery drains, charging fails and power is lostThe ICCU, which combines the on-board charger and the converter that powers the 12 V system, can fail on the Ioniq 5, Ioniq 6 and EV6: it cuts AC charging, drains the 12 V battery and, in the worst case, the car loses power and stops. Hyundai and Kia have recalled units built from 2021 to 2024.Repair: €2,000–€5,000
- Medium severityFrequency: Very frequent1.5 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.
- Medium severityFrequency: Very frequent1.8 HybridThe 12V battery drains on the C-HR and Corolla hybridsYes: on the first-generation C-HR hybrid, the 12V battery is one of the most frequently reported faults: it runs flat after a few days standing or on short trips, and the car will not start. The ADAC and Toyota itself point to it as a cause of faults on the C-HR and Corolla.
- Medium severityFrequency: Very frequent2.0 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.
- High severityFrequency: OccasionalBMW Serie 6 E63/E64Battery drain and loose positive cableThe battery and alternator are frequently cited by Fiches-auto, and there is a recall for the battery's positive cable, which can work loose.
- High severityFrequency: 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.
Frequently asked questions
Can I drive with code P0683?
Autodoc Club says that driving in the short term is possible, but that you should expect cold-starting problems and repair it soon, because the problem may get worse. With the engine hot or warm the glow plugs are not needed to start, according to TroubleCodes.net, but from cold the car may be hard to start and prolonged cranking strains the battery and starter motor.[1][2][6]
What is the difference between P0683 and P0670?
Klavkarr describes P0670 as a fault in the glow plug control module, while Autodoc Club and TroubleCodes.net define P0683 as a fault in the communication circuit between that module and the ECU. The causes the sources cite overlap (module, wiring, fuses and power supply), so both codes are diagnosed in a similar way.[1][2][4]
What is the difference between P0683 and P0684?
P0683 indicates a communication fault between the ECU and the glow plug module; P0684 adds that the ECU detects an abnormal, out-of-range or implausible voltage in the communication circuits. The causes TroubleCodes.net cites are the same.[2][6]
Does code P0683 affect petrol cars?
No. Both Autodoc Club and TroubleCodes.net associate it with diesel engines, which are the ones that have glow plugs and a module that controls them.[1][2]
What is the glow plug control module?
It is the unit that, according to BorgWarner, defines the timing, intensity and duration of the current the glow plugs receive and that maintains constant communication with the engine ECU. Older systems used a relay that acted as a switch.[3]
Will I pass the MOT with code P0683?
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.[7]
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.
- Código OBD2 P0683: causas, síntomas y cómo corregirloAutodoc Club · Technical documentation · consulted 4 October 2026 · in Spanish
- P0683 – Glow plug control module/ECM/PCM communication -malfunctionTroubleCodes.net (BAT Auto) · Technical documentation · consulted 4 October 2026
- Glow Plug Control UnitsBorgWarner Aftermarket · Manufacturer · consulted 4 October 2026
- P0380 / P0670 fault codes: glow plug diagnosis and repairKlavkarr · Technical documentation · consulted 4 October 2026
- On-board diagnosticsWikipedia · Other source · consulted 4 October 2026
- P0684 – Glow plug control module/ECM/PCM communication range/performanceTroubleCodes.net (BAT Auto) · Technical documentation · consulted 4 October 2026
- 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