1998 740iL Cruise Control Issue

[Edwin740]

Hello everyone,

I have had issues with my cruise control for quite a while now. At first, it was that the gears had stripped out. My friend and I 3D printed an exact replica that should work great (hasn’t melted in the hot engine bay yet). However, this still has not solved the issue. The cruise control will light up and them time out without so much as a hint of engagement. Recently after resetting the software in the hidden menu I noticed that the motor was spinning, but not engaging when the car was parked. I imagine it was trying to calibrate itself? I tested pins 2 and 3 and the electromagnet does engage. I don’t know what else could be causing it not engage, however I’m sure there are many things that could cause this. Any insight would be appreciated.

Thank you

[stevick]

Most here will suggest you scan for fault codes, which would substantially assist in the diagnostic process. Absent that, all I can offer is my own experience with a cruise control issue, which may be entirely different than yours. Mine had the ABS and Triangle cluster lights lit and cruise control would not engage (the cluster cruise control indicator would light, though I can't say it ever timed out). The problem was with the signal used by the cruise control, which is sent from the RR wheel speed sensor. No signal, no cruise. Resolving that restored my cruise control and the ABS/ASC.

[Timm]

Check your brake lights - the cruise control actuator used the brake light bulbs as the ground connection - it is done this way so that if the brake lights come ON (the brake pedal is pressed) then the clutch loses the ground and releases the throttle. This is why LED's can't be used as brake lights, they take too little current (you need all three to be fitted with tungsten bulbs).

[Edwin740]

Thanks all, I checked all of your suggestions and found them to be working. Confused, I got a used actuator to rule it out, and that fixed the problem. If I ever figure out precisely what was wrong with the old actuator, I will let you know.