Skip to content
MotorFiable
en

Electrics and electronics

Problems with the control units: symptoms, cost and affected models

We have documented 51 faults with the control units in 47 cars. The most important by severity and frequency: electronic faults with the doors, boot and screen (suspected BSI control unit) (Peugeot 408), multiplex electrical system and hands-free card faults (Renault Laguna II) and DC/DC converter control unit fault with risk of short circuit and fire (Mazda MX-5 IV). At an independent garage, the repair costs from €600 to €800 depending on the engine or car.[1]

Documented faults
51
15 of high or critical severity
Cars analysed
47
with at least one fault on this part
Affected models
47
car generations in our database
Garage repair
€600–€800
Depending on engine and car, including VAT

3 sourcesHow we work

How it works and why it fails

Control units and comfort electronics (BSI, SAM...)

Comfort functions (lights, doors, wipers, alarm...) are managed by control units such as the BSI on Peugeot and Citroën or the SAM module on Mercedes, connected in a network (multiplexing). If one fails or gets damp, warnings appear in a cascade with no apparent connection between them.

What to do

When several electrical faults appear at once, ask for a full network diagnosis before replacing individual parts. Check whether water is getting into the cabin or the control unit area: it is the cause of many of these faults.

General explanation by MotorFiable. The specific faults of each engine and car, with their sources, are on the linked pages.

Common symptoms

The symptoms that come up most often in the documented faults with the control units. Open each one to see what other faults cause it.

Problems with the control units by car

Faults documented on specific cars, which occur with any engine. From most to least important.

  1. 1High 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.
  2. 2High 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).
  3. 3Critical 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.
  4. 4Medium 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.
  5. 5High severityFrequency: OccasionalJaecoo 7Loose ECU wiring harness: engine warning light and stallingIn March 2026 Jaecoo issued a recall in the UK for up to 7,500 Jaecoo 7 1.6 TGDI units (April-December 2025) because a clip on the engine control unit (ECU) wiring harness may not be secured properly, with a risk of the engine warning light coming on and the engine stalling. In Austria it affected 15 J7 AWD petrol cars. The plug-in hybrid is not affected.Repair: €0
  6. 6High severityFrequency: OccasionalMazda CX-60Incorrect software in the Dash-ESU and other control units of the hybrid CX-60Yes: two Safety Gate alerts from May 2025 (AR058A and AR056A) correct the software of several control units in hybrid CX-60s. With the hybrid system running, the demister, the seatbelt warning and the 360° camera may fail, and in the 'T3 M Hybrid Boost' variant the engine may stall at idle or fail to restart.
  7. 7High severityFrequency: OccasionalMitsubishi ASX IOverheating of the engine control unit power relayThe relay that powers the engine control unit on 2015 ASX cars can overheat and fail; the power supply is then cut, the engine warning light comes on and the car may stall and not restart. Mitsubishi corrected it with a recall that replaces the relay (Safety Gate A12/0099/18).
  8. 8High severityFrequency: OccasionalMitsubishi LancerETACS control unit fault: headlights and wipers can stop workingYes: in 2015 a campaign was registered over a non-conformity in the ETACS electronic control unit of Lancers built between October 2008 and September 2010, as a result of which the headlights or wipers, among other systems, could stop working. The remedy described is to replace the control unit if its manufacturing date falls within the affected range.
  9. 9High severityFrequency: OccasionalMitsubishi LancerOverheating of the engine control unit relay and the valve lift control relayA Safety Gate alert from October 2018 (A12/1462/18) states that the engine control unit relay or the valve lift control relay can heat up abnormally and the engine can stall while driving. It covers the 2015-2016 Lancer and Lancer Sportback, and also Outlander models.
  10. 10High severityFrequency: OccasionalMitsubishi Outlander IIETACS control unit fault that can leave you without headlights or wipersA non-conformity in the ETACS control unit could disable the headlights, the wipers or other systems on the 2008-2010 Outlander II. Mitsubishi corrected it with a recall (Safety Gate A12/1379/15) that replaces the control unit on affected cars.
  11. 11High severityFrequency: OccasionalMitsubishi Outlander IIIOverheating of the engine control unit power relayThe engine control unit relay (or the valve lift control relay) on the 2014-2017 Outlander and Outlander PHEV can heat up abnormally and fail; the engine may stop working and not restart. Mitsubishi put it right with a recall that replaces the relay (Safety Gate A12/1462/18).
  12. 12High severityFrequency: OccasionalVolvo S40 IIWasher fluid leaking from the windscreen washer pump into the wiring and central electronic module on the Volvo S40Washer fluid can seep into the pump, run down the wires to the central electronic module and affect several functions of the car or, in serious cases, cause a fire. UK campaign R/2011/163 covers the C30, S40, V50 and C70 and replaces the pump's wiring harness.
  13. 13High severityFrequency: OccasionalVolvo V50Washer fluid leaking from the windscreen washer pump into the wiring and central electronic module on the Volvo V50Washer fluid can seep into the pump, run down the wires to the central electronic module and affect several functions of the car or, in serious cases, cause a fire. UK campaign R/2011/163 covers the C30, S40, V50 and C70 and replaces the pump's wiring harness.
  14. 14Medium severityFrequency: CommonBMW Serie 3 E46Central locking and immobiliser failure due to worn relaysThe central locking can become intermittent or stop responding to the remote, and the immobiliser can fail sporadically when starting; gebrauchtwagenberater.de attributes both faults to wear in the relays of the control modules, and fiches-auto.fr records numerous testimonies of unreliable locking.
  15. 15Medium severityFrequency: CommonCitroën C3 IErratic behaviour of the BSI and electronic modules (control unit, wipers, lighting, car radio)The BSI (built-in systems interface) and other electronic modules in the C3 I can cause odd behaviour in the central locking, the wipers, the lighting or the car radio; it is the non-powertrain fault category most cited by owners on fiches-auto.fr, with 62 cases recorded.
  16. 16Medium severityFrequency: CommonMercedes-Benz Clase M W164SAM and EZC electronic module failure caused by water ingressAccording to the owner testimonies collected by fiches-auto.fr, the body electronics of the M-Class W164 (SAM and EZC modules and the ZGW gateway) account for around 37 cases of failure, some of them attributed to water getting in through the rear light seals.
  17. 17Medium severityFrequency: CommonMercedes-Benz Clase S W220Control unit and electronics faults on the Mercedes S-Class W220Yes: AUTO BILD and AutoScout24 agree that electronics are the W220's weak point, with faults in engine management, the immobiliser and other control units that are usually replaced whole. On fiches-auto, 34 out of 100 owners mention the electronics.
  18. 18Medium severityFrequency: CommonOpel Vectra CInstrument cluster and CIM electronic module faultsThe Vectra C's instrument cluster can fail because of a connector problem, and the CIM electronic module, which manages several functions of the car, is responsible for various electronic faults, according to gebrauchtwagenberater.de; fiches-auto.fr adds warning lights that come on for no reason and a trip computer showing incorrect data.
  19. 19Critical severityFrequency: RareToyota C-HR IThe immobiliser can switch from "Ready ON" to "Ready OFF" while the car is movingOn vehicles built between 2020 and 2023, a weak standard immobiliser design can let the car enter "Ready ON" mode without properly verifying the key and then switch to "Ready OFF" while driving, which can cause the hybrid system to shut down on the move. Toyota fixes it by inspecting the vehicle at an official service centre.
  20. 20Medium severityFrequency: OccasionalAlfa Romeo GiuliaElectronics and control unit faults on the Alfa Romeo GiuliaAccording to the reports collected by fiches-auto.fr, electronic faults (control units, dashboard warnings, unstable parking sensors) are the most cited non-engine area for the Giulia: 22 cases out of 103 reports.
  21. 21Medium severityFrequency: OccasionalCitroën C4 IElectronic faults in the COM2000 module and the BSI unitWith 76 cases in the same survey, electronic faults are another of the most cited systems: indicators, horn or the ABS, ESP and airbag warning lights can fail because of a fault in the BSI, the unit that centralises much of the electronics, or in the COM2000 stalk, often intermittently.
  22. 22Medium severityFrequency: OccasionalCitroën C8Repeated electronic faults in the BSI control unit and wiringThe fiches-auto.fr page counts 27 C8 owner reports of repeated electronic faults (BSI, automatic lights, controls); cars from 2002-2005 would be the most exposed to damp-related faults.
  23. 23Medium severityFrequency: OccasionalCitroën Xsara PicassoRusted BSI (built-in systems interface) with general electrical failure (2002-2003 cars)On 2002-2003 cars, fiches-auto.fr documents a BSI (built-in systems interface) fault caused by rust, with a defective circuit causing widespread electrical faults and no clear prior warning; the repair costs around €700 in France.Repair (garage): €600–€800
  24. 24Medium severityFrequency: OccasionalLancia ThesisControl unit faults and electronic warnings with no real causeThesis owners describe sensitive electronics: control units that go haywire, warning lights that flag non-existent faults, and an alarm that goes off for no reason. These are owner testimonies, not statistics.
  25. 25Medium severityFrequency: OccasionalLand Rover Range Rover IIIOnboard electronics faults: immobiliser, warning lights, GPS and camerasAccording to fiches-auto.fr, 24 testimonials cite serious electronic faults: a car that will not start because of the immobiliser, multiple warning lights on, GPS and camera that stop working or clocks that fail, often linked to a weak battery or corroded earths.
  26. 26Medium severityFrequency: OccasionalMercedes-Benz Clase E W211SAM module faults, false airbag warnings and battery drain on 2002-2003 carsThe first E-Class W211s (2002-2003) account for more electronics complaints: the SAM module can fail and cause lights or wipers to stop working, the front passenger seat occupancy mat triggers airbag warnings for no reason, and in 2005 Mercedes-Benz issued a software update for the on-board power supply manager because of battery drain.
  27. 27Medium severityFrequency: OccasionalMercedes-Benz CLK C208Electrical faults: window winders, electric seats, alternator, starter motor and immobiliserAuto Bild (2007) identifies the electrics as the weakest point of the CLK C208: immobilisers, alternators and starter motors fail, as do comfort features such as the electric windows and electric seats. AutoScout24 (2009) adds occasional lighting faults, including xenon headlights.
  28. 28Medium severityFrequency: OccasionalMercedes-Benz CLK C208Faults in the airbag control unit, instrument cluster and COMAND systemAutoScout24 (2009) records problems with the airbag control units on the CLK C208 (coupé and convertible), and Auto Bild (2007) cites reader complaints about faults in the central instruments and the COMAND system.
  29. 29Medium severityFrequency: OccasionalMercedes-Benz SLK R171Door control unit failure and other electrical faults on the SLKElectrical faults are the most cited problem on the SLK R171 on fiches-auto.fr (13 cases or more): door control units (400-650 euros in the cases cited), heated seat controls, airbag warning lights and ESP. There is no known recall.
  30. 30Medium severityFrequency: OccasionalMINI Cooper R56FRM module (footwell module) on the Mini Cooper R56 that locks up after a voltage dipGebrauchtwagenberater.de notes that the R56's FRM module reacts badly to voltage dips (a flat battery, jump-starting) and can leave the lights and electric windows uncontrolled.
  31. 31Medium severityFrequency: OccasionalMitsubishi ASX IControl unit software that misjudges the 12 V battery's deteriorationUnsuitable engine control unit software could misjudge the deterioration and state of charge of the battery in ASX cars built between June 2010 and September 2011; according to gebrauchtwagenberater.de, this could make the car suddenly stop. The DVSA records a recall that reprograms the software.
  32. 32Medium severityFrequency: OccasionalOpel AdamElectronic control unit (BCM), immobiliser, remote key and parking sensor faultsAccording to the owner reports collected by fiches-auto.fr, there are 8 cases of electronic faults on the Adam: immobiliser, remote key, on-board computer, parking sensors and blind spot alert. The listing attributes them to the body control module (BCM) and the wiring. There is no known recall.
  33. 33Medium severityFrequency: OccasionalPeugeot 206Cascading electrical warnings caused by the BSI (fuse box)When the BSI (the fuse and relay box that centralises much of the electrical system) receives an unstable signal, several warning lights can come on at once with no mechanical fault behind them; it is usually due to a corroded earth, damp connectors or a weak battery.
  34. 34Medium severityFrequency: OccasionalPeugeot 207Cascading electrical warnings from the BSI (fuse box)When the BSI (the fuse and relay box that centralises the electrical system) receives an unstable signal, several warning lights (ABS, ESP, airbag...) can come on at once without any mechanical fault behind them; it is usually down to a corroded earth, damp wiring or a weak battery.
  35. 35Medium severityFrequency: OccasionalPeugeot 308 IBSI and electric window electrical faultsThe BSI (the control unit that manages much of the electrical system) can fail and light up several warning lights at once with no real mechanical fault behind it; the electric windows can also stop raising or lowering the glass intermittently.
  36. 36Medium severityFrequency: OccasionalPeugeot 807Cascading electronic faults in the multiplexed electrical systemThe fiches-auto.fr page (30 of 175 owner reports) describes electronic faults that light up the airbag, ABS and ESP warning lights at the same time and affect the lights, wipers, GPS or sensors, often because of a corroded connector or low battery voltage.
  37. 37Medium severityFrequency: OccasionalRenault Vel SatisHands-free card, GPS and control unit faultsElectronics is the most cited area on fiches-auto.fr for the Vel Satis (26 cases): faults with the hands-free card, readers, control units and the Cabasse GPS navigation system. We have found no official recall.
  38. 38Medium severityFrequency: OccasionalTesla Model YRisk of a short circuit in the central computer (Hardware 4.1) that can leave the reversing camera without an imageOn Model Y cars with the Hardware 4.1 computer (built 2023-2025), a reverse current when the car is switched on can cause a short circuit on the central computer board and leave the reversing camera without an image; Tesla fixes it with a software update or, if needed, by replacing the board.
  39. 39Medium severityFrequency: OccasionalVolvo S80 IIVolvo S80 wipers that run by themselves or do not work because of a central electronic module software errorIn 2009 Volvo recalled (R/2009/046 in the UK) a batch of S80, V70 and XC70 cars because a software error in the central electronic module could make the wipers run without being activated or not work at all. The remedy is to update the module software.
  40. 40Medium severityFrequency: OccasionalVolvo V70 IIIVolvo V70 wipers that run by themselves or do not work because of a central electronic module software errorIn 2009 Volvo recalled (R/2009/046 in the UK) a batch of S80, V70 and XC70 cars because a software error in the central electronic module could make the wipers run without being activated or not work at all. The remedy is to update the module software.
  41. 41Medium severityFrequency: OccasionalVolvo XC70 IIIVolvo XC70 wipers that run by themselves or do not work because of a central electronic module software errorIn 2009 Volvo recalled (R/2009/046 in the United Kingdom) a batch of S80, V70 and XC70 cars because a software error in the central electronic module could make the wipers run without being switched on or not work at all. The remedy is to update the module's software.
  42. 42High severityFrequency: RareOpel Insignia BMoisture in the central locking control unit (2018 campaign)A 2018 campaign covers Insignia Bs built between February 2017 and March 2018: poor sealing at the A-pillar lets moisture into the central locking control unit, with a risk of short circuit and fire.
  43. 43High severityFrequency: RareToyota RAV4 VHybrid stalls while driving because of the RAV4's immobiliser (2019-2023)A 2024 campaign covers hybrid RAV4s (2019-2023) whose immobiliser could allow 'Ready ON' mode without recognising the key, and then switch the system off, even while driving.
  44. 44Medium severityFrequency: RareAudi A8 D5Moisture in the engine control unit due to a connector without a sealing pinAudi recalled 583 A8 and S8 built between April 2018 and October 2020 because a sealing pin was missing from a connector on the engine control unit, allowing moisture in, with emergency mode or stalling possible.
  45. 45Medium severityFrequency: RareMercedes-Benz GLB X24712 V battery: key, starting and control unit faultsAccording to the fiches-auto.fr page, the GLB's 12 V battery causes key, starting and control unit faults; two GLB 200 d owner reports (one at 123,000 km, with an MRM box) document it. It is a pattern of owner reports with no associated campaign.
  46. 46Medium severityFrequency: RareOpel Insignia BWater ingress into electronic modules and rear light unitsTwo testimonials on fiches-auto.fr describe water ingress: into an electronic module on a 2.0 Turbo (70,000 km, 2020, with the alarm and starting affected) and into the rear light units of a 2.0 diesel.
  47. 47Medium severityFrequency: RareRenault Twingo IImmobiliser fault on the Twingo IOver the years the Twingo I's immobiliser can stop working and the car will not start; the German source says a new unit costs at least around €1,000, and sometimes the culprit is the key.
  48. 48Low severityFrequency: OccasionalCitroën C2Window motor and BSI module faults on the Citroën C2On the C2, the reports on fiches-auto.fr cite around 28 electrical mentions: window motors, door wiring and BSI module faults, plus false airbag warnings. No public recall is on record.
  49. 49Low severityFrequency: OccasionalMitsubishi Colt VIElectrical faults: bulbs, immobiliser and batteryThe Colt VI is cited for faulty bulbs, immobiliser faults and flat batteries, and the immobiliser was among the fault points in the 2010 ADAC statistics.
  50. 50Low severityFrequency: OccasionalSmart Forfour ISAM unit and electrical faults from translation between systemsThe Forfour 454 combines Mitsubishi engine management with Mercedes body electronics through a SAM unit, and that combination causes electrical quirks: warning lights that misbehave and CAN communication errors. A Mitsubishi-only workshop may not recognise them.
  51. 51Low severityFrequency: RareFiat Panda IIEngine cutting out due to a loose main relay, a damp ECU connector or a loose earthThe Dutch roadside assistance service ANWB flags three minor Panda II faults that stop the engine: the main relay in the fuse box that vibrates loose, damp in the engine control unit connector, and a loose earth cable.

Problems with the control units by make

Problems with the control units in your car

4 cars have several documented faults with the control units. Choose yours to see only the ones that affect them, by engine and by year.

Mercedes-Benz 1
Mitsubishi 2
Opel 1

How much it costs to repair a fault with the control units

Sorted from the most expensive repair to the cheapest. Prices in Spain including VAT (parts and labour); what each figure includes is on its page.

How we calculate costs · The most expensive repairs across all engines

OBD fault codes with the control units

The codes the ECU usually stores when this part fails: what they mean, causes and what to check.

Frequently asked questions

Which cars have problems with the control units?

Among those we have analysed: Peugeot 408 (electronic faults with the doors, boot and screen (suspected BSI control unit)), Renault Laguna II (multiplex electrical system and hands-free card faults), Mazda MX-5 IV (DC/DC converter control unit fault with risk of short circuit and fire), Fiat Stilo (electrical and electronic faults in the multiplex system), Mitsubishi ASX I (overheating of the engine control unit power relay), Mitsubishi Lancer (ETACS control unit fault: headlights and wipers can stop working), Jaecoo 7 (loose ECU wiring harness: engine warning light and stalling) and Mazda CX-60 (incorrect software in the Dash-ESU and other control units of the hybrid CX-60). In total, 47 cars with documented faults with the control units.

How much does it cost to repair a fault with the control units?

It depends a lot on the engine or car. At an independent garage, from €600 to €800; at a dealer, from €0 to €0, including VAT, based on the 2 faults with a documented cost. The most expensive is rusted BSI (built-in systems interface) with general electrical failure (2002-2003 cars) (Citroën Xsara Picasso).

What symptoms does a fault with the control units cause?

The most frequently cited in the documented faults: intermittent electronic warnings or sensor faults, electric windows or central locking not responding, esp warning light on or flashing, engine stalls or cuts out while driving, battery goes flat while the car is parked and screen or infotainment system freezes or restarts.

Sources

Every fact on this page links to its source. If you find an error, let us know.

  1. Fiabilité Citroën Xsara Picasso (1999-2010) : pannes et rappelsfiches-auto.fr · Technical documentation · consulted 27 September 2026 · in French
  2. Jaecoo 7 recalled: quarter of all 2025 UK cars going back to dealersAuto Express · Motoring press · published 6 March 2026 · consulted 30 October 2026
  3. Omoda & Jaecoo J7 AWD: Probleme mit dem Innenraum-Boden-KabelbaumÖAMTC · Official body · published 2 March 2026 · consulted 30 October 2026 · in German