Converting to Motronic 1.3

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Motronic 1.3 was introduced to E30s in September 1987 when the facelift cars were launched, and was the final version of the engine management system used on these cars. For those with older vehicles, it can be worthwhile stripping out your older system to fit Motronic 1.3. Here's why and how it's done.


The main thing anyone is going to want to know is why upgrade to M1.3 from the earlier systems. If your car is running fine as it is and you are happy with keeping it original, both in terms of performance and function then there probably isn't that much point in going to the effort. However if you are looking to increase performance or you are having running issues then it might be a good option, some may say necessity on the performance side of things.

• Improved accuracy of sensors and event timings for better fuelling and timing.

• Capability for a lambda to be fitted.

• Ability to remap chips for increased performance.

• Able to run a MAF instead of an AFM, again for increased performance.

• Better fault-finding with reduced number components with a sturdier construction.

• Better replacement parts availability.


Motronic 1.3 is a fairly complex system, but is based on previous versions of the Motronic system. You will need all of the following parts to get Motronic 1.3 up and running, but you may already have some of these parts depending on what your current engine management system is.

From Jetronic From Motronic 1.0 From Motronic 1.1
Crank Position Sensor & Bracket Crank Position Sensor & Bracket
Toothed crank wheel Toothed crank wheel
Engine bay loom Inc Injector Loom Engine bay loom Inc Injector Loom
Cylinder Identification Sensor Cylinder Identification Sensor
Oil Level Sender Oil Level Sender
Oil Pressure Switch* Oil Pressure Switch*
Distributor cap and rotor arm
Temperature Gauge Sender
Camshaft dust cover
Camshaft rotor adapter
Air Flow Meter
  • Oil Pressure Switch is optional as the loom can easily be modified to use the existing switch.


Any E30 can be converted to Motronic 1.3, but it is important to know what system you have fitted currently. If you're not sure, check the Engine Management page.

If converting from Jetronic you will need to follow this guide through all three stages listed below, if you are starting with M1.0 you only need follow the second and third section and to upgrade from M1.1 you can just skip to the last section.

Once you know what you have, you can get hold of the components you need for the conversion and start from the appropriate step below:

From Jetronic

Camshaft rotor adapter (7) and dust cover (6)



Disconnect the battery, since we will be working with the Ignition system. You may also want to consider removing the radiator to give you more space to work.

Locate the distributor, mounted on the front of the engine block near the alternator. All of this assembly needs to be removed, which is done by prying apart the dust cover, disconnecting the wires, and unclipping the cap. Then undo the 10mm nut holding the distributor in place, and pull the entire unit up and out of the engine block. Make sure not to remove the the oil pump drive shaft, which also drives the distributor.

In the space where the distributor was, you will need to fit a blanking plate. You can also remove the Ignition Control Module (mounted to the inner wing) including its wiring. This should include disconnecting a green wire to the ignition coil, which will be replaced when you fit the new loom.

If your distributor had vacuum advance/retard, then you will also have some rubber hoses lying around the area. Follow these back to where they meet the rubber boot or intake manifold and disconnect the pipes at those points. Blank off any holes with bolts and PTFE tape.

Now move up to the head, and located the camshaft timing sprocket. You will need to attach the camshaft rotor adapter and dust cover to the front of the sprocket; all of the holes should be in place for this to simply screw in. Once this is done, you will be able to mount the rotor arm and distributor cap to the head of your engine. Make sure that all the HT leads are connected in the right order.


Two styles of C101 plug were fitted to the E30, and you will most likely have the older style plug on a Jetronic vehicle. Rather than converting your new loom to the old plug, is it better to convert your body loom plug to the new style round connector. Try to obtain this C101 from the same donor vehicle, as well as the length of wire that runs to the fuse box. Then you will start the slow procedure of cutting off the old plug and joining the wires to your new plug. All the pinouts are on the C101 page.


Unfortunately, the injectors on older engines are high-impedance, and their electrical operation is incompatible with the newer Motronic system. You will therefore need to fit newer injectors with a lower impedance.

Air Flow Meter

The Air Flow Meter is specific to each engine, but they are all essentially the same style. To remove the AFM, undo the jubilee clip to the rubber boot, unclip the electrical connector, and unscrew the 10mm nuts securing the AFM to its mounting bracket. Now wiggle and lift the unit, complete with air filter, out of the engine bay. With the entire unit removed, the AFM can be unscrewed from the air filter housing and replaced, then the assembly returned to the engine bay. You will not be able to connect the new AFM to the existing plug, but the engine loom is covered later in this article.

Temperature Sender

Jetronic systems also utilised a different version of the Brown Plug which drives the Temp Gauge. These older plugs were two-pin units, while your new system will only have one wire to connect to it. You will therefore need to replace your old Brown Plug for the new one-pin version, or adapt the new loom.

Now continue to the next step.

From Motronic 1.0

The main difference from M1.0 to M1.3 is the Crank Position sensor. All systems before M1.1 used two sensors mounted into the gearbox, while M1.3 uses one sensor at the front of the engine. You'll be fitting this new sensor, as well as a toothed wheel that sends a pulse through the CPS to the ECU. You'll also be fitting a Cylinder Identification sensor, which tells the ECU which spark plug is firing.


Crank Position Sensor

The Crank Position Sensor is a single unit that tells the ECU the engine is turning. Without this signal, none of the Fuel or Ignition circuits will run, so it's therefore essential to get this fitted and working.

The Motronic 1.3 CPS replaces the two sensors you currently have in the bell housing of your gearbox. You will not need to remove your existing sensors, but since you are removing the engine loom, they will be disconnected. In their place, you will be fitting a single sensor to the front of the engine with a mounting bracket, as well as a toothed wheel for the sensor to "read".

Here you can see the CPS in position on the front of the block, ready to pick up the signal off the crank pulley. All M20 blocks have the threaded holes ready to fit this.

The most involved aspect is fitting this toothed crank wheel. This involves removing the radiator and the fan before you can access the existing pulley. Once you've got those off you need to remove the fan belt and water pump pulley then undo the bolts holding the existing crank pulley, pull it off and fit the toothed pulley in place of the old vibration damper, this has a locating pin so can only go on in one position, then slide on the original pulley and bolt back together.

On the left is the toothed crank pulley you'll need to fit(note the 7th hole which is for the locating pin), then on the right is the PAS pulley that then bolts in place, you can use your existing one.

While you've got all those cooling parts removed, you'll find it easier to mount the CPS bracket. The bracket is held in place with two M8 bolts, low down on the block on the exhaust side. With the bracket in place, the sender can be fixed to it, and the wiring routed around the front of the engine. The plug should be mounted under the ICV, where it will connect to the main engine loom.


The Motronic 1.3 system uses a wiring harness to connect all the sensors up to the ECU. Since the Motronic 1.3 ECU is more complex, it is fed by an increasing number of wires to better read and control the engine. You will therefore have to disconnect all the plugs on your existing loom, unclip it, and remove it completely.

One end of the loom is the ECU plug. So that you can understand how everything fits together, check the pinouts for Motronic 1.3. The ECU plug passes through the bulkhead next to the battery. You will have to gain access to the ECU to unclip it, then feed the ECU plug through the rubber grommet into the engine bay. Quite often the prefacelift cars have a smaller hole in the bulkhead so you may have to remove the outer casing on the ECU plug to get it through the hole.

The other big connector on the loom will be the C101 plug. The C101 connects the engine loom to the main vehicle Loom, supplying a switched power feed as well as sending data back out to the Instruments. The C101 doesn't need to be touched at all other than to carry out the checks on pin 19 which are explained on the C101 page.

What wiring does need doing is for instrumental purposes only and is easiest to carry out on the ECU plug end. There are two wires you need to cut on the ECU plug and then connect to the C104 plug which will now be unconnected following the removal of the old loom. The easiest thing to do is cut the matching plug from the old loom and plug it into the loose plug in the car. Then you need to connect pin #1 (Blk/Blu) on the C104 to pin #6 (Blk) on the ECU, the second connection to make is to connect C104 pin #3 (Wht) to ECU pin #32 (Wht/Blk), C104 pin #2 is not used.

Once these changes are made, you need to feed the new loom into position and secure it using either the existing clips or with cable ties. You can then route all the plugs to their relevant locations; see the engine loom page for a wiring diagram.

Oil Pressure Switch

This is located on the exhaust side of the engine block, this is vital as it's linked to the instrument cluster and if it comes on you want to be turning the engine off ASAP! Jetronic and M1.0 use a spade connector whereas M1.1 and M1.3 use the same type of multipin plug other engine sensors use (although still only using one wire). The function of both types is identical. There are two simple options to get this working, either chop the plug off the new loom and use a spade connector or for the more professional job swap the switches over.

M1.0 oil pressure switch with a spade type connector.

Oil Level Sensor

The existing sensor, located on the sump, uses a different plug to the Motronic engine loom, but operates in the same way. You therefore have two solutions to this; you can either cut the old plug off the existing loom and join it to your new loom, or replace the sensor with a newer one.


The Cylinder Identification sensor is a simple device that connects to the final HT lead in your engine. This will be No 4 or No 6, depending on your engine. You cannot separate the CID from the HT lead, but fitting is simple. Just unplug your existing HT lead, replace it with your new CID-equipped lead, and run the CID plug to its connector on the engine loom.

Now continue to the next step.

From Motronic 1.1



The differences between M1.1 and M1.3 all lie in the ECU, in the way that it processes the information it receives and acts upon it, especially with regard to fault codes. Therefore, upgrading from M1.1 to M1.3 is as simple as plugging in a new ECU. The ECU must be matched to your engine, from September 1987 or later. For a list of ECU codes, see the ECU page.