top of page

BMW SMG to Manual Swap (Fix Cruise Control)

Updated: Jan 9

To properly enable cruise control, the SMG to manual gearbox conversion on a BMW requires a few more steps.

I will walk you through the steps necessary to reactivate your cruise control. The procedures are simple, requiring only a few electrical connections and reprogramming.

  • Make a closed circuit and remove the temperature sensor

  • Identifying connections and wiring

  • Connect the oil temperature sensor to the gear selection switch and test it

  • Check that pin 2 is receiving ground

  • Programming in the manual mode

  • Program the DME

This article will discuss converting from SMG to manual swap and having problems with the cruise control. It's a basic wiring schematic that I'll show you.


Table of Contents:


Remove the SMG Temperature Sensor & Create a Closed Circuit

On the SMG, the temperature sensor will be in the bell housing, which is no longer utilised on manual gearboxes.

There is a harness that will be utilised for the gear selection switch; just unhook it since this wire was previously connected to the SMG module.

If the conversion is already complete, the SMG module will be disconnected. Install the holder into the back of the transmission, you should have a plug hanging from it.

As a result, you'll attach the loose connection to the gear selector switch socket. Remove the plastic guide to ensure correct connection.

For testing reasons, we leave it open but attach a piece of wire by simply inserting it into the connection to establish a closed circuit.

Identifying Connections & Wiring

So we need to figure out which wire to utilise. Below is the only wiring schematic you'll need.

SMG wiring diagram

This is an SMG wiring diagram, and you can see that you have a transmission fluid temperature sensor, connector x5238.

SMG wiring diagram X5238 connector

We need to verify the continuity test on the connection where you created a closed circuit. Ensure that leg 13 and pin 31 are connected in a closed circuit.

SMG wiring diagram

One will be attached to the DME pin number 20, connector number X60002, and the other to the clutch switch pin number 20, connector number S805.

For the time being, we only need to use two cables. On the SMG module, we must identify the connector X53004.

Simply pull the tabs up and slide the connection out, then repeat the process on the opposite side.

A variety of wires will be connected to pin number 31. BMW uses them to connect several grounds to a single circuit.

We're no longer using the SMG module, so you don't have to worry about identifying the correct wire; just remove it.

We need to find out which one will be pin number 31, therefore we'll use pin number 13 to test the continuity.

You can use a needle to remove it or a snap-on pin remover tool. You only need to unlock it, push it down, and pull it out.

It will be attached to DME pin 20 and connector x60002.

Evaluate the relation between 13 and 31. You should have a closed circuit since you attached a wire to the oil temperature sensor connection.

Connect the Oil Temperature Sensor to the Gear Selection Switch

Connect the oil temperature connection to the gear selection switch and test its functionality by changing gears in the vehicle to confirm it is operational.

If you discover anything isn't quite right, you know where to look; your selector switch is most likely not correctly placed.

Check That Pin 2 Is Receiving Ground

Make sure you have a strong ground from the pin connection number 2 on the gear clutch switch, which should be on your clutch pedal.

There are four pins in there, and we'll pull the wire from pin number two through the panel and to the electrical box.

If everything is correctly linked, you should have ground when the car is switched on but as we depress the clutch, you should lose ground.

This cable will link to the transmission's gear position switch and then back to the DME, where the gear selector switch will be connected, and it will only open in a closed circuit.

If you put the car in neutral and lose ground, or depress the clutch and lose ground, this consistent ground will be interrupted.