Choose a brand

Abarth
Alfa Romeo
Aston Martin
Audi
Bentley
BMW
Bugatti
Cadallic
Caparo
Caterham
Chevrolet
Chrysler
Citroen
Corvette
Dacia
Daihatsu
Dodge
Ferrari
Fiat
Fisker
Ford
Honda
Hummer
Hyundai
Infiniti
Jaguar
Jeep
Kia
Koenigsegg
KTM
Lamborghini
Lancia
Land Rover
Lexus
Lotus
Maserati
Maybach
Mazda
McLaren
Mercedes Benz
MG Cars
Mini
Mitsubishi
Morgan
Nissan
Noble Automotive
Not Shown
Pagani
Peugeot
Porsche
Proton
Renault
Rolls Royce
Rover
Saab
Seat
Skoda
Smart
Subaru
Suzuki
Tata
Tesla
Toyota
Vauxhall
Volvo
VW

Problems

Bosch Motronic with 35 pin (2 rows) or 55 pin (3 rows) connector

 

Bosch Motronic common failure symptoms
(35 & 55 pin ECUs)

Bosch Motronic engine management ECUs with integral ignition power stage are increasingly suffering failure as ECUs age. These ECUs are commonly fitted to Alfa Romeo, BMW and Vauxhall(GM) cars from 1987 up to the introduction of distributorLESS systems. Click here to see photo of ECU.

To identify Motronics with integral ignition power stage look at the underneath of the ECU. There are 2 small screws (Philips or Torx head) which locate the connector body to the ECU base plate and either 2 or 4 larger screws (Philips or Torx head). ECUs with 4 larger screws have integral ignition power stage – if 2 of the larger screw holes are blanked off with plastic plugs then there is a separate ignition power module(s) and THIS PAGE DOES NOT APPLY – THERE IS A SEPARATE IGNITION AMPLIFIER LOCATED IN ENGINE COMPARTMENT. Click here to see photo of ECU. NOTE:Bosch Motronic ECUs with 35 pins fitted to Peugeot or Citroen cars (up to 1992) do NOT have integral ignition amplifier – there is an ignition amplifier module located below inlet manifold and this is the most likely cause of loss of spark on 2 cylinders on these 2 particular makes.

Symptoms

1) Car breaks down (sometimes without warning) – apparent loss of spark and NO fault codes.
2) There may be a history of intermittent starting or misfire problems but note below for Vauxhall cars.

Diagnostic Checklist

ALL VAUXHALL CARS with this system – REPLACE large fuel injection relay for vehicle non start or running problems – before condemning anything else!

1) Check that injectors and fuel pump are working normally.
2) If yes, check for very low ignition pulse – very weak spark sometimes visible.
3) If yes, check all LT and HT connections for defects and exchange coil if available.
4) If above OK then ECU confirmed failed.

If in doubt about whether ECU is cause of problem on your car, try our low-cost ECU inspection service. This is fast, low-cost and many Motronic ECUs with this common problem can be fixed during inspection – avoiding costs of rebuild.

DO NOT REMOVE ECU COVER – THESE ECUs FEATURE HIGHLY SENSITIVE MICROELECTRONIC INTEGRATED CIRCUITS THAT CAN BE DAMAGED BY NORMAL ENVIRONMENTAL ELECTROSTATIC CHARGES.