So I need to revive a thread
https://acurazine.com/forums/showthr...ghlight=speedo

From the other threadstarter:

1) it seems like my speedometer is DEFINTIELY not matching up to how fast my car is going...and i know there is a margin of error but a few days ago i got pulled over going 51 when like 10 min before I got pulled over i was sure the speedo read 40 on a 30 zone.

2) i noticed that when i go WOT, my speeddo drops back down kind of oddly...
(i.e. - i'll accel to 80MPH...and when i let off on the gas, usually, your needle will decrease pretty steadily right? but of late, the needles "LOOKS" like it gets stuck or that it returns back to 0 in a very rough and jerk manner...that's the best way i can describe it. <in addition, alot of times when i accel, i get like this really sudden jerk in acceleration after i hit like the 30mph mark...and when i decel, i get this same "jerk" and that's when the speedo needle kinda seems stuck>



I am having the same issue, anyone know of a fix?
I changed out the cluster but that didn't solve anything.

 

According to the service manual, the "Countershaft speed sensor" sends pulses to the PCM that then feeds the speedo.
If you've replaced the speedo, then either the PCM is faulty or the "Countershaft speed sensor".
Here is the diagnostic and replacement procedure:

 

this is why i luv acurazine

 

what about wheel/tire size? that will throw of the speedo

 

but also bad alternators (mainly the AC ripple put into the DC line), can cause some F***ing strange things to happen while also being quite random at the same time

so also make sure you got a good battery too, and the alternator charging properly

 

My theory to that

Was working fine for 6 months > Now not working.
I'm on 18x7.5 235/40

Plus, it's ridiculously off. Like on the highway sometimes 30+ mph off.


Battery is a new duralast gold 51r, alternator may be fucked up. Not sure.

 

tires are a bit on the smaller side, i have 245/40, which are basically exactly the same diameter as stock

 

anyone know if the part number for the countershaft speed sensor is
28810-P7W-004 or 28810-PCJ-014