Cruise Control
 

1999 convertible, 93,000 miles. Cruise Control has not worked since I acquired almost two years ago. The long haul down I-5 to Southern California had me wishing for a functioning CC to give my right leg and foot a bit of relief. While I'm sure there are several things that could be causing this malfunction, does anyone have any experience in correcting same? And any estimates what I might be getting into? and by that I mean, how deep will I be getting into my wallet?
Chuck
Olympia, WA

If I remember correctly the '99 XK8 used the AJ27 engine which had the CC imbedded into the ECM software and used the throttle stepper motor to maintain the speed.

First question: Do you have a CEL/MIL? For many of the codes the first line in the list of actions is to disable the CC.

The CC switch on the console is a common problem. Try cleaning or replacing the switch and inspecting the wiring connections at that point.

Beyond that it gets complicated.

Another problem area that prevents Cruise from working is the break light switch. Take a quick look and see if your break lights are always on, that is a good indication of a bad switch. The switch on the pedal actually contains 2 micro switches one for the break lights and one for the cruise control. If the cruise thinks you are breaking it won't come on.

A second common problem is failure of the brake pedal switch. It has two microswitches, one is for the brake lights and you would get a message on the display if it fails. The second set disconnects the cruise control, and if that fails there may not be a message.

You can check the switch by disconnecting it and using a meter. The outer pins are one set, the inner the second set. One set should have continuity when the pedal is pushed, that's the brake lights. The cruise control circuit is then open, but closes when the pedal is released.

Yes, my CC worked sometimes, when I replaced the switch it works great. But check fuses, wiring connectors first. That switch is a ******* to replace.

Thank you all. I