I cleaned the MAF & throttle body today and after complete it runs well but somehow the tachometer stopped working. I searched threads and the tachometer and speedometer are on the same fuse so I need to troubleshoot where the signal got lost. Any assistance would be appreciated.

 

Disconnected negative terminal overnight and then ran a DTC check this morning which came back with no codes. It’s odd the tachometer is stuck near 1250 RPM & a reset didn’t at least “cycle” the gauge. Any help would be appreciated.


Tachometer stuck on this RPM and does not move

 

What was sprayed into the throttle body?

 

CRC Throttle body cleaners.

 

Strange. I doubt if the 2 are related. Seriously, it just sometimes happens like that, but obviously I can't say for sure. The only time I had an analog gauge stop working it was the sending unit.

 

Try thumping the top of the dash. The LS400 had a know issue with sticking tacho needles and a thump normally returned them to normal function.
IIRC it was caused by ancient grease getting hard and jamming the needle. The jolt dislodged it and fixed the problem.
The tacho is normally fed it's signal by the ECU these days. If a sensor plays up you will get a code and she will run poorly.

 

It's a failed stepper motor in the cluster. The ECM is still getting a signal from the crank sensor if the engine runs.

 

Thanks, makes sense as “rapping” it didn’t do anything. Is there a vendor you know of that replaces the stepper motor and rebuilds/tests the instrument cluster?

Second, are there instructions anywhere on how to remove the cluster?

 

These clusters don't use steppers.

 

Found these guys online.
https://www.instrumentclusterstore.c...t_clusters.htm
No idea if they are any good or not but may be worth a call.

 

Did you ever find a fix for this, mines is doing the same