Reading time 4 Min.

The Controller (ECU) is a central element in modern cars and takes on essential functions for the engine. If the control unit, which is also called Engine control unit is known to be defective, it can lead to various problems. In this article we will explain how it works, Symptoms, address causes and repair options for a defective control unit. The ECU, a Engine management computer, is responsible for regulating various processes such as throttle control, ignition timing and turbo pressure. It processes data from over hundred sensors such as the outside temperature and the accelerator pedal position. If the complex systems malfunction, professional repairs are required a professional are essential.

Is the control unit defective?

A defective control unit can manifest itself through various symptoms: the Engine control lamp (MIL display) lights up in the instrument cluster and the vehicle is running Emergency run, Jerking of the car or uneven engine running, specific Error codes such as P0354 in the Siemens Simtec 71 series, which indicate problems with the ignition coil control, are also typical.

Causes of a defective engine control unit

Short circuit in the cabling or components: This can cause the control unit to burn out and is often caused by external influences such as incorrect vehicle starting.
Vibrations: Long-term vibrations can damage sensitive electronic components. Examples of this are the bonding wires in the control unit, as in the Magneti Marelli IAW 59F / 59M / 5AF / 5AM, which is used in Fiat vehicles.
Temperature influences: High temperatures, especially in summer, can put a lot of strain on the control devices. An example is this Delphi Delco Multec HSFI in various Opel models, which is prone to heat damage to the bonding wires due to assembly on the cylinder head.

Overhaul of the control unit

If the control unit is defective, various specialists online offer an overhaul. On their website you can usually find an overview of the control devices that are eligible for an overhaul. Contact the provider for further information about the products and services. Overall, it is crucial to recognize the signs of a defective control unit early and act accordingly. This way you can ensure that your vehicle functions optimally and avoids unnecessary damage.

Main functions of an control unit (ECU):

- Control of engine functions such as throttle, Ignition timing, boost pressure.
- Processing of data over 100 sensors (e.g. outside temperature, accelerator pedal position).
Symptoms of a defective control unit:
- Check engine light (MIL indicator) lights up.
- Car drives in Emergency mode.
- Shaking of the vehicle or uneven engine running.
- Specific Error codes like P0354 on the Siemens Simtec 71 series.
Common causes of defects in the engine control unit:
- Short circuits in cabling/components: Caused by external influences such as incorrect vehicle starting.
- vibrations: Long-term exposure leads to damage to the electronics. Devices like this are affected Magneti Marelli IAW 59F / 59M / 5AF / 5AM in Fiat models.
- Temperature influences: Problems especially in summer. For example, this is Delphi Delco Multec HSFI sensitive to heat in Opel models.
Repair and overhaul of control devices:
- Professionals offer professional Overhauls for defective control devices.

FAQ: Detecting and repairing a defective control unit

Signs of a defective engine control unit – Irregular engine running: Engine stops while driving or runs rough. Activation of the check engine light: Common sign of problems in the engine control system. Increased fuel consumption: Unusually high consumption may indicate a control unit problem. Deactivated immobilizer: Unscheduled deactivation may indicate ECU failure.
Costs for repairing a control unit –Repair costs: About average 250 to 450 EUR. Cost of a replacement part: depending on the vehicle between 750 and 1.000 euros; higher in individual cases. Additional Costs for removal and installation.
Repair options for an engine control unit – specialist workshops: Repairs require special electronic equipment; Consultation with the workshop necessary.
How the engine control unit works – control, control and monitoring of engine functions: ECU (Engine Control Unit) is a crucial component in modern cars.
Number of control units in modern cars – Up to 150 control devices: Modern cars have a complex network with up to 5 km of cables and 50 kg in weight. Data transmission: There will be up to 25GB data per hour replaced.
Position of the engine control unit – Different locations depending on vehicle model: In water tanks, in the interior behind the speedometer or in the engine compartment behind the battery.
Dealing with the Check Engine Light – Vehicle with the check engine light on: If the engine is running normally, you can continue driving, but with caution. Flashing check engine light: Indicates significant problems, better stop and call a tow truck.
Identification of the control unit – Bosch number on the label: Important for identification, usually begins with 028 or 026.

thematically relevant posts

In our category Tips, products, information & Co We have reviews of car or accessories manufacturers, new ones Tuning Wiki Terms or one or two leaks published.

Steering gear repair: costs, instructions and tips!