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Discussion Starter #1
Car details:
2000 RS
32,000 km
Cobb EJ253 w/ closed deck
TD06-20g
AEM EMS series 1
STI Type R Instrument Cluster (I unfortunately no longer have the original Instrument cluster from my car)

So after having this car sitting in storage for the last 8 years, I'm finally putting it back on the road. Only problem is that I've never been able to get the speedometer working and I'm hoping you guys can help me out with this one. I've spent probably close to 100 hours just trying to get this thing working. After relentless troubleshooting I'm still stuck. Here's a quick summary of where I'm at so far...

The car is running off of an AEM ems, series 1 for a 2002-2005 Subaru WRX. Everything works great except for the speedometer. I can read vehicle speed on my laptop when plugged into the ems so the speed sensor and all of the wiring between the speed sensor and ems are correct and functioning properly. The speed sensor is an oem transmission mounted 3 wire sensor. The voltage of the speed sensor wire into the ems reads 0 when the car is not moving. Because the ems is reading vehicle speed, when the car is rolling it is assumed that the wire from the speed sensor to the ems is sending the pulsed 5v signal from the speed sensor. This same wire that goes from the speed sensor to the ecu branches off and runs to the instrument cluster as well so the cluster should be getting this same signal. I've cut this wire from the ems to the instrument cluster. If I tap this cut signal wire back together on itself as fast as I can with the car at stand still (no signal being sent from speed sensor) I can get the speedometer needle on the cluster to reach about 15km/h. If I take this same wire from the instrument cluster and tap it to ground as fast as I can instead of to the wire leading to the ems I can get the speedometer to reach about 40km/h. With the speed sensor wire cut between the speed sensor and the instrument cluster there is no change to the speed reading I get out of the ems.

With the speed sensor wire cut and no longer attached to the instrument cluster, I am getting a voltage readout of 5v from the speed sensor input on the back of the instrument cluster. This is the pinout that when jumped to ground or to the ems I get the needle to move on the speedometer. I find it very odd that this pin is holding a constant voltage because this is an input, not an output, as far as I know. I thought maybe it is possible there is a short inside the instrument cluster, so I picked up a second instrument cluster out of a '99 rs and am having the exact same issue with this cluster and I doubt 2 different clusters happen to have the exact same internal issue so I believe this cancels out any chance of a short inside the cluster.

Does anyone have any insight what is going on here or any other options I could try to get this stubborn thing working properly?
 

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needs more cowbell
95L, 07 2.5i, R6
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9,307 Posts
Are you sure the three wire sensor is the correct sensor? Maybe that model needed the two wire sensor. Is it the original transmission and sensor for that model / the one the cluster is for?
 

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Discussion Starter #3
The 3 wire sensor is correct for the car/transmission/cluster yes. The transmission is the original one that came with the car.
 
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