These are the factory instructions to testing and troubleshooting the E30 cruise control system with additional clarification:

Using backprobes like this fit perfectly into the pin holes of the blue cruise control module plug:

*The English translation was incorrect for the last step and so it has been overwritten in green to match the correct German version of this workflow.

** Step 3 (the step before the step in green), denotes 0 volts at “Off”. Per the schematics, Off is either up or down for pre 1988 and so both up and down should produce 0 volts.

For the below first step:

The two steps involving the 7 pin connector are to be performed with the connector still connected.

7-pin connector is located under the driver side underpanel, right by the pedals. Follow the black with red strip cable from the cruise control actuator to the firewall grommet, then inside you will see the same cable meet a 7 pin plug (C209). Pin numbers are marked on the back of the plug.

These last two steps are performed with the connector disconnected and power applied on the female plug side (cable leading to actuator).

The 7 pin connector has two types of pins, 1.6mm and 3.5mm (female going to actuator, male going to cruise control module), test leads can be made if desired to make measuring and probing easier.

***pictured are 4 test leads, but you really only need two to perform the above tests. One 1.6mm male lead and one 3.5mm male lead.

PN for those pins can be found here:

E30 connector pin alternatives to OEM BMW

Pre 1988 cruise control:

Post 1988 cruise control

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