Engine management system (VW Golf 4)

Location of SIMOS engine management system components in the engine compartment with 1.6-I engine

• 1 - Hall sensor electrical connector (black);
• 2 - Hall sensor. On the upper casing of the toothed belt;
• 3 - Lambda sensor, 50 Nm. Mounting position with automatic transmission in the exhaust manifold;
• 4 - Lambda sensor electrical connector. On the bottom of the car, on the right;
• 5 - intake manifold switching valve;
• 6 - SIMOS control unit;
• 7 - throttle body;
• 8 - coolant temperature sensor;
• 9 - air flow meter. With a temperature sensor for the air entering the engine;
• 10 - place of connection of the ground bus to the gearbox;
• 11 - ignition coils. With ignition control unit;
• 12 - electrical connector of the knock sensor;
• 13 - engine speed sensor;
• 14 - Electrical connector of the engine speed sensor (gray);
• 15 - knock sensor;
• 16 - fuel injectors;
• 17 - fuel pressure regulator;
• 18 - Canister with charcoal;
• 19 - Magnetic valve of the charcoal canister

Various engine management systems are installed on cars with gasoline engines.

Engine	Engine management system
Engine 1.4-I	AHW/ AKQ Magneti Marelli 4AV
Engine 1.6-I	AEH/ AKL Simos 2
Engine 1.8-I	AGN Motronic 3.8.5
Engine 1.8-I	Turbo AGU Motronic 3.8.3
Engine 2.3-I	AGZ Motronic 3.8.3

The use of an electronic engine management system has the following advantages:

• ensures optimal fuel supply to the engine in all operating modes, resulting in reduced fuel consumption while maintaining the vehicle's dynamic performance;
• due to more complete combustion of fuel, as well as the use of a catalyst, the emission of harmful substances along with exhaust gases is reduced;
• since the electronic engine management system detects and records faults in its memory, troubleshooting and detection is significantly accelerated;
• the engine management system sets the optimal ignition timing, moment and amount of fuel supplied to the engine in all operating modes. The engine management system also interacts with other vehicle systems, in particular, with the automatic transmission control system or with the anti-theft system.

The engine management system components are very reliable and require virtually no maintenance. Maintenance only requires replacing the air filter and spark plugs. Since complex, expensive equipment is required to check, adjust, and repair the engine management system, this work must be performed at a specialized service station.

During vehicle operation, there is no need to adjust idle speed or CO content in exhaust gases.

Warning: When working on the ignition system with the ignition on, be careful because you may receive an electric shock from the high-voltage part of the ignition system. People with pacemakers are not recommended to check or repair the engine management system. Turn off the ignition before disconnecting or connecting any component of the ignition system or test leads.

(The text is copied from this portal: «vwmanual»)

Warning: The fuel system is under constant pressure even after the engine is turned off, so before performing any work on the fuel system, the pressure must be relieved.

Warning: To prevent the possibility of accidental electrical short circuits and damage to electronic components of the engine management system, always remove the ground cable from the battery.

Before performing any work on the engine management system, recall the faults stored in it from memory. Also check the fuel system and the engine air supply system for leaks.

Normal operation of the engine management system is possible only when the voltage in the vehicle's network is not lower than 11.5 V.

If after work on the engine management system the engine starts and stops after a short time, the engine may be switched off by the anti-theft system. In this case, recall the faults stored in the memory and, if necessary, adjust the engine management system.