My cluster speedo is behaving stranglely for a couple of months. It will not show my actual speed, instead it will fluctuate erratically around the actually speed. Sometimes my rpm on my Defi ZD will go crazy for a while, suddenly showing rpm reading of more than 10000 when my cluster rpm is normal. My mechanic and I tried many ways to identify the problem, from changing battery, putting ground cables, plugging out my Defi ZD, checking for loose wirings,but to no avail.

One day, I decided to plug in my OBD scanner and suddenly my speedo on my cluster and rpm on my defi reads perfect. No more wild swings. Once I plug out, speedo goes crazy again and sometimes Defi rpm goes crazy. I tried plugging in my flashpro and the problem is solved too. Seems like if something is plug into the OBD port, my speedo will behave normally. Anyone here encounter this problem. Its getting really frustrating. Pls help.

 

Last time I saw an erratic Speedometer, the ground on the back of thr cylinder head was loose.

 

I rechecked the ground wire again. The wire is secured to the bracket. But the bracket which is on the head was loose. I tightened the bolt and problem solved. Thanks Bill.

 

The ground wire should go directly to the cylinder head, not the bracket.