Help with speed sensor
 

I am running an Elite 2500 on my 95 USDM Rx-7.

The Haltech is not reading the drive train sensor (transmission output speed). The speedometer on the dash works fine as before, but the haltech is not reading the signal. This is causing all sorts of tuning issues.

I have a custom wiring harness, built by my tuner. Everything on the harness is plug and play, except having to splice these wires on the cabin side into the harness (pictured below). As you can see the speed signal from cluster 1M is wired to SPI 1 which is the correct input. I am really stumped on this one. Any advice would be helpful.
https://cimg2.ibsrv.net/gimg/www.rx7...8f843ef4b4.jpg

Assuming the sensor is wired to the ECU correctly, it sounds like you need to calibrate the ECU to read the sensor correctly. I'm not a Haltech guy, but this problem sounds very similar to what I had to go thru with my Link G4+ to get the ECU to correctly read the OEM speed sensor on the tranny so I could use any of the Link's features that require a speed input (e.g., cruise control via DBW, gear detection, etc..). Anyway, it sounds like your wiring harness guy did your harness similar to how I did - the speed sensor goes to the dash via the OEM wiring, and there's a parallel connection from the speed sensor output to one of my Link ECU's digital inputs.

In my case, after I wired my car, the dash speedo worked perfectly as it did before, and the speed sensor was being "seen" by the ECU, but the speed being displayed on my laptop with the PCLink ECU tuning software was WAY off from reality - pulling out of my driveway it would read like 80MPH, when I was doing maybe 10. To calibrate the speed sensor to the Link ECU, I had to go thru a specific procedure that you can be done on the fly with a helper driving the car, or by taking logs & adjusting settings after the fact, then re-doing to verify the calibration. The calibration procedure involved driving at a steady, known speed (use your speedo or GPS/phone app for "truth data") for a minute or two, and then adjust a frequency scaling factor in the ECU's tuning software menu that is associated with the digital input used fro the speed sensor. Get the scaling factor right, and the ECU's displayed speed will match ground truth.

Update: I had tried multiple times to recalibrate the ECU for the sensor, but it was not getting a signal at all. During one of these sessions, trying to recalibrate I had the cruise control on and voila! it works, but only while the cruise button on the top right of the cluster is turned on. The cruise does not have to be set it just has to be ready.

Guess the next question is, how do I get it to work without the cruise control button depressed?

That's odd, my best guess is your wiring is missing a ground return path between the speedo sensor and the Haltech. And when you switch on the cruise, it provides that missing ground path somehow. How to fix it might be easier to explain with a schematic - below is an excerpt from my schematic diagram for my FD's speedo sensor wiring to the Link ECU.


https://cimg4.ibsrv.net/gimg/www.rx7...529b33e4dc.png

As you can see in the yellow highlighted paths, the 2 terminals coming from the OEM speed sensor are tapped to connect to: (1) one of my Link's digital inputs (DI1) and (2) to the Link's Sensor Ground (GND) before going into the OEM harness at the X14 connector (Y/R and Y/W wires on X14 of OEM Dash harness), which in turn routes to the instrument cluster to drive the speedo & cruise functions. The blue highlighted OEM connectors are the speed sensor (C1-08) and the X14 OEM interface connector, which connects the OEM ECU/emissions (EM) harness to the Dash (D) harness.

For anyone down the road trying to bypass the stock cluster in/out signal conditioning for a factory 5MT FD trans to a Haltech - just cut the green/red wire going into the stock cluster, and crimp it inline with the yellow/red wire beside it on the cluster connector. Pin 3E G/R to Pin 3C Y/R. Once you've made that connection, change the ECU settings for your VSS to reluctor, and roughly 8200 pulses was what worked for me. Effectively double the values of when it was being output as a sine wave by the cluster itself. I suspect a cap or cpu inside the factory gauge cluster is failing for me, causing the speed output to ECU to screw up, even though the speedometer on the cluster itself is working perfectly fine. I did have to disable automatic reluctor settings and had to dial those voltages a little to keep it from generating noise at idle.

I tried using the Yellow/White wire as mentioned above and just got all kinds of chaotic noise that the auto-calibrate did something like 300000 pulses compared to the 8200 or so it should be. I'm assuming that while that connector is connected with a functioning stock speedometer, it may be getting grounded by the cluster.