Thread: Cruise - Speed Control Input Voltage

Originally Posted by Graeme

I suspect that the Gap tool shows the brake light switch status - it's not something that I recall having checked.

I doubt that it will, even if it is faulty. Should be NC if no brake action, will become open when the brake pedal is moved. If it has failed open, then the system will see it as the brake being activated and stop any further bootup.

Originally Posted by Old Farang

Should be NC if no brake action, will become open when the brake pedal is moved.

It is both NC and NO. 2 separate sets of contacts. The car gets awfully confused if they don't actuate at very close to the same time.

Originally Posted by BradC

It is both NC and NO. 2 separate sets of contacts. The car gets awfully confused if they don't actuate at very close to the same time.

Years since I dug into this stuff, but my understanding is that 1 contact is for the brake light, and the other for the cruise control. There is a string of sensors in that loop for the cruise control, but the brake pedal contact "should" not get confused, even allowing for CanBus.

Need to remember that CanBus was used for the very early cruise controls that had a vacuum actuator and a bit of steel wire connected to a thing called a carburetor!

Originally Posted by Old Farang

Years since I dug into this stuff, but my understanding is that 1 contact is for the brake light, and the other for the cruise control. There is a string of sensors in that loop for the cruise control, but the brake pedal contact "should" not get confused, even allowing for CanBus.

Need to remember that CanBus was used for the very early cruise controls that had a vacuum actuator and a bit of steel wire connected to a thing called a carburetor!

One contact is for the brake light, but that's also monitored by the CJB, ECM and ABS modules. That connection allows the ABS module to turn on the brake lights when in HDC mode.
The second contact is connected directly to the ABS module as a sensor input. If the ABS module sees an implausible signal because of a dodgy contact then it causes cascading faults across the network.

Driving recently on a long fast graded track at about 80 with CC on when you come into a patch of more serious corrugations the CC would switch off which I imagine was wheel speed sensor related some mismatch outside parameters.

That should have produced an ABS fault but not if the cause was the brake pedal bouncing a little.

Originally Posted by Graeme

That should have produced an ABS fault but not if the cause was the brake pedal bouncing a little.

Very possible that scenario

From hazy memory the CC drops out if any form of DSC event happens, and even turning the DSC off doesn't completely disable all elements of it, it just stops you getting bogged on the beach.

Just checked. Service manual says "Even if DSC is deselected, driving manoeuvres with extreme yaw or lateral acceleration may trigger DSC activity to assist vehicle stability". I'm pretty sure I triggered it skating across a corrugated gravel road on an off camber corner.