I installed my TST box and noticed my speedo would occasionally "jump" up about 5- 8 mph while driving for a second and then return to read the correct speed. It does this at all different speeds and there is no equal time frame it happens, but about every minute or so it jumps. I called TST and they said there was no way it was the box cause it does nothing to the trans. But this morning My check guages light came on and the amp guage read zero. I checked code it was 0622. That is for generator not reading/charging. I cleared code and started it again, it ran for about a minute with the guage reading almost 10 amps/volts then tripped code 0622 and went to zero again. I bypassed the TST and there was no more code and the spedo does not jump anymore. But the guage reads low for about 2 full minutes before going up above 14 like normal. I did this several times all the same. So I assume the TST box could be making my spedo jump as it is okay when bypassed. It does get power from a fuse tap that controls tranny. But the amp/volt thing has me worried.

 

I would try a different power source location for the box.
The low voltage right after starting it up could just be the intake heater doing it's job.

 

I dont think its the heater. It has never been on that long before and its about 50 degrees today.

 

Any ideas anyone???? In my old 98 factory service manual it says it could be a loose or bad connection or maybe a bad PCM! ouch......

 

My speedo does that too but only since installing my Race anti defueler. I figured that was the cause. I never thought it could be the TST.....

 

I have the same with RAD and TST. RAD says it will do this. When you play around with the ECM sensors something screwy is gonna happen....as long as it makes power....I don't care. ks

 

I turned my TST off yesterday for the drive home. Miraculously the problem went away! I guess it is the TST causing it and I just never noticed it before I installed the RAD. Oh well. It doesn't seem to hurt anything and the cruise control keeps a steady speed so I don't care....