need help trouble shooting cruise control

[bastianshaw]

Im about to just start throwing parts at this thing, ive checked both the clutch and brake switches nothing happens

Has anyone else lost cruise control what did you do to fix it?

[Quadrajet]

I haven't had this problem myself. But the system may not be sensing ground from the taillights, keeping it from working.

[bastianshaw]

yes im aware about the ground where/how would I check that?

[Quadrajet]

On the CC unit itself it's #9. A Green/Red wire. This is from the BMW troubleshooting manual- For Cruise control to be engaged, pin9 must sense ground through stoplights.

I have seen it mentioned that one stoplight is the one it senses through, whether it be LH or RH I don't remember. Hope this helps.

[bastianshaw]

On the CC unit itself it's #9. A Green/Red wire. This is from the BMW troubleshooting manual- For Cruise control to be engaged, pin9 must sense ground through stoplights.

I have seen it mentioned that one stoplight is the one it senses through, whether it be LH or RH I don't remember. Hope this helps.

pretty sure its the RR tail, has anyone EVER fixed an inop CC?

[jlevie]

Rather than throwing parts at problem while hoping for a favorable outcome, use section 6571-0 of the ETM (http://wedophones.com/BMWManualsLead.htm) for trouble shooting. Specifically check to see that the module has power on pin 1, that the switch inputs (pins 2, 4, 5, & 7) are valid and that signals on pin 3 on an auto and pin 9 are correct, and that the speed input is present on pin 6.

If you don't find and problems there, the module or the cruise control unit is bad.

[bastianshaw]

Rather than throwing parts at problem while hoping for a favorable outcome, use section 6571-0 of the ETM (http://wedophones.com/BMWManualsLead.htm) for trouble shooting. Specifically check to see that the module has power on pin 1, that the switch inputs (pins 2, 4, 5, & 7) are valid and that signals on pin 3 on an auto and pin 9 are correct, and that the speed input is present on pin 6.

If you don't find and problems there, the module or the cruise control unit is bad.

sweet this is the reply i was looking for, you are talking about the module near the cruise stalk behind the dash right?

are "signals" just voltage?

[jlevie]

I don't know if the cruise control modules for all production variants have the same home. But every one I've seen has been mounted above the glove box.

[bastianshaw]

Above the ecu toward the seats?

[jlevie]

Yes above the DME.

[Gregs///M]

Make sure your yellow/blue wire is connected behind he speedometer. Its a single plug that plugs into the green speedo connector. That the speed sense wire for the CC

[honda.lioness]

My friend recently bought a 1988 e30 BMW 325i, with the cruise control not working. She mentioned that it had originally had an automatic transmission. The prior owner had swapped in a manual tranny. I checked all the wiring from the control unit to {the brake switch; the steering column switch; the actuator under the hood; and the speedometer}, both for signals and continuity. Nothing seemed wrong until I got to the cruise control unit's pin 3. Pin 3 goes to the "start relay" via connector C143. Connector C143 carries a signal from the "start relay" to the control unit for BMWs with automatic transmission. It turns out connector C143 was sending a ground signal to the cruise control unit and keeping the cruise control from engaging. Per some sites on the net that talk about auto-to-manual tranny conversions, I disconnected C143. The factory service wiring diagram sort of mentions how C143 is superfluous for manual tranny BMWs. The cruise control now works perfectly.

Connector C143 is on the driver's side, outboard, under the dash, not far from the hood release. Connector C143 has a blue/brown wire going to the cruise control unit and a green/black wire going to the start relay. With an automatic transmission, when the car is in park or neutral, C143 grounds pin 3 on the cruise control unit. With a manual transmission, there should be no ground at pin 3.