Engine Management

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Engine management is pretty much what is says in the tin. It is a system that controls the running of the engine.


Engine management in its simplest form controls the engine via fuelling and Ignition timing. The entire E30 range has some form of engine management system, from the most basic carburetted M10, through the various guises on the M20 to the most modern on the M42 with seperate coil packs. Aftermarket systems are also available for those running highly tuned engines allowing the user manual control over multiple settings.

All systems employ a number of sensors placed in the engine and Drivetrain, which fed data via the Loom to an ECU. While early systems were analogue based, later systems were digital and offered better control over the engine in all driving environments.



Main artice: L-Jetronic

Jetronic was the first form of engine management fitted to the E30. It comprised of a rudimentary ECU and a variety of analogue sensors dotted around the Drivetrain, and provided the most basic of fuel injection management.


Main article: Motronic

Motronic is the trade name given to a range of digital engine-management systems developed by Bosch. This superseded the more primitive L-Jetronic system in 1987.

All Motronic ECUs contain a fuel map with an injector opening time for basic conditions of speed and load. Information is then gathered from engine sensors such as the AFM, CPS, CTS, and TPS. As a result of this information, the ECU will look-up the correct injector pulse duration right across the engine rpm, load and temperature range.

Motronic 1.0

Main article: Motronic 1.0

This is the first version of Motronic engine management used on fuel injected E30s, this is what is fitted to pre-facelift cars. The obvious things to spot to tell this from M1.1 & M1.3 are the fact this has an ECU with a number ending 073 and that is has 2 pickup sensor attached to the bellhousing instead of a single one on the front of the block.

Motronic 1.1/1.3

Main article: Motronic 1.3

Motronic M1.1 and then M1.3 were the most advanced versions used on the E30 8v and 12v engines. This can be found on all facelift cars with M40 and M20. M1.1 and M1.3 can be differentiated by their ECUs.

Motronic 1.7

This is the most modern management system that an E30 left the factory with. It was only fitted to the M42 engined 318iS. This did away with a distributor and coil, the use of individual coilpacks was introduced.

Fault Codes

For vehicles equipped with the "Check Engine" light in the dash cluster, it is possible to obtain fault codes to diagnose problems with the Motronic system. Learn more about Motronic fault codes.



All Engine Management systems depend on a number of sensors to identify what's going on in the engine at any given moment. These sensors provide data on air intake and crank position, while later Motronic systems can also measure spark and exhaust data to keep the engine running smoothly. The sensors fitted to E30 engines are:


Main article: ECU

The ECU is the brain of each system, receiving data from the sensors and controlling engine operations accordingly.

Because of the wide variety of systems used over the life of the E30, and that each ECU is specific to the engine, there are a multitude of ECUs available. Check the list below to identify what ECU you should have in your vehicle.

List of ECUs

The following list shows which ECUs were fitted to which vehicles:

ECU Number System Models From/To
0260 200 005 Carburettor 316 1982-
0280 000 318 L-Jetronic 318i 1983 - 84
0280 000 330 L-Jetronic 318i 1984 - 87
0280 001 301 L-Jetronic 320i and 323i 1982 - 84
0280 001 309 L-Jetronic Later 320i
0280 001 308 L-Jetronic Later 323i
0280 000 310 L-Jetronic Late 323i
0261 200 174 Motronic 316i 1988 Onwards
0261 200 157 Motronic 318i 1987 - 88
0261 200 175 Motronic 318iS 1989 onwards
0261 200 164 Motronic 325i Auto 9/87 onwards
0261 200 381 Motronic 320i 1987 onwards
0261 200 172 Motronic 320i 1987
0261 200 073 Motronic 325i Chrome bumper 1985 - 87
0261 200 173 Motronic 325i Plastic bumper 9/87 onwards
0261 200 380 Motronic 325i 8/88 onwards
0261 200 071 Motronic Early 195/200bhp M3 and Evo 1
0261 200 090 Motronic M3 Evo II
0261 200 091 Motronic M3 with 215bhp
0261 200 092 Motronic M3 Sport Evo
0261 200 042 Motronic 325e until 9/85
0261 200087 Motronic 320iS
0261 200 074 Motronic 325e 9/85 onwards (Low compression)


Engine Plugs

The main engine wiring harness is a loom that contains plugs for all the sensors within the management system. It also connects to sub-looms to control engine operation such as the injectors and emission control systems.

This wiring harness connects to the main vehicle Loom through a multi-pin plug known as the C101. The C101 went through an evolution during the lifetime of the E30, and Jetronic looms therefore have a completely different C101 to Motronic systems.

Jetronic systems also employ a secondary connector, C104. Located next to the ECU, it acts as a power supply as well as providing tachometer data to the instruments.

WARNING: One of the most significant differences across the looms is Pin 20. On early vehicles, Pin 20 is a brown earth wire, while for some later vehicles Pin 20 is a live, unfused red/yellow wire for the ABS system. If you are changing your engine, CHECK PIN 20 ON BOTH SIDES OF THE C101 PLUG before connecting the battery.

If you have a brown wire connected, cut it away from the pin, and make sure the free end can't come into contact with anything. If it is red/yellow, then leave it alone. Of course, if the body side of your C101 has a red/yellow wire on pin 20, and your new engine loom has nothing connected to this pin, you need to add a wire, capable of carrying about 15A, from either of the terminals marked '87' on the DME relay socket to pin 20 of the the C101 plug, otherwise your ABS braking system won't work.

Facelift vehicles also feature a secondary plug. Known as the C191, it sits under the throttle body and connects up the injectors, engine temp sensor and temperature gauge to the main engine loom. A number of fuel-related issues, including rich running, can be attributed to corrosion of this plug.

Diagnostic Plug

The engine wiring harness also contains a diagnostic plug, allowing you to tap in to loom for a number of functions, such as bypassing the starter motor and resetting the service indicators.

ECU Plug

Main article: ECU Pinouts

The ECU plugs are also different over the years, to accommodate the increasingly sophisticated management systems. This makes it impossible to fit an earlier ECU to a later loom.

Unlike the main vehicle loom, the ECU plug enters the cabin on the drivers side of the car, via its own dedicated hole in the bulkhead. In this way, the ECU and loom can be removed and changed without affecting the main wiring of the car.

DSCF4446.jpg DSCF4449.jpg
ECU plug from a 1986 325i ECU plug from a facelift 320i


Convert to Motronic 1.3

Aside from the system specific to the M42 engine, E30s perform best under Motronic 1.3 engine management. Not only does it provide the smoothest running of the engine as a whole, but also gives you access to modifications in the form of performance chips and Mass Air Flow intake upgrades.

Learn more about converting to Motronic 1.3.


Megasquirt is a complete aftermarket engine management system, designed to replace whatever existing system you have. It offers a more sophisticated platform for tuning your engine, and is a popular choice for those who have already extensively modified the mechanical aspects of their engine. Considering the most powerful engine on the E30 is the M20B25, then it stands to reason that the vast majority of Megasquirt installations are fitted to that engine. Learn more about Megasqirting your M20.


Another aftermarket engine management system, the Unichip is manufactured by Dastek. Offering the same dynamic control as Megasquirt, the Unichip also saves up to 5 different maps which can be selected automatically, given you the ability to switch between Power and Economy modes as wanted, or any range between the two.