I'm getting the P1637 code on my 99 XK8, and the cruise control is not working. The codebook says says:
P1637 CAN ABS/TCCM token message
When ECM detects fault:– Inhibits cruise control– (Idle speed control quality deteriorates)
Possible Reasons:
CAN open circuit fault – ABS/TCCM to ECM
CAN short circuit fault ABS/TCCM failure
ECM failure
Does anyone know the best approach to solving this problem?

 

You have any of many, many modules not responding to the CANetwork as it is expected.

First and easiest is to verify that your battery voltage is good. The car is capable of being started at lower voltage than required for the electronics.

Second, do a hard boot by removing the negative battery cable from the battery post and touching it to the positive post.

The ABS/Traction control system is famous for turning on and off lights. You might have to wait until a fault stays in long enough to be read.

 

I am going to move your post over to the XK8 section. I also see that you put another post in the General Tech Help and I will remove it. I feel that you will get the help you need in the XK8 section.

 

Many cruise control issues on the early cars were due to faulty brake switches...monitored by the abs module, no doubt. There is a diy video or pdf w instructions in the FAQ sticky in ths subforum if u want to try that...minimal outlay of funds