It's been bugging me and it seems like no one has a fix so here it goes... My speedo and PFC was reading 30mph at idle. I tried reading some threads and tried a few things, but I really don't want to start guessing but now it reads 0mph. I hope I didn't fry anything! I have the gauge cluster out right now but the PFC reads 0... There's some wires that were cut and others that I don't know what they are. I'll take pics tomorrow, but where can I start with this?

 

Wirering diagram

 

since both are reading incorrectly I would start looking at the speed sensor.

 

Yellow with blue had something tapped into it before, just curios. My main concern is the yellow with black stripe is cut and not hooked up to anything.


this wire was tapped into and hooked up to a relay. Not sure what the relay was for?


yellow with black stripe was hooked up to the same relay.


this is disconnected, not sure what its suppose to hook into?


Black with red stripe, not sure what its suppose to hook into?


This was the relay...

Please help!!!!! This is driving me crazy

 

Its tough to tell where that yellow/black goes to in the ECU, if you download this you can find out;

http://www.wrex-racing.com/html/fd/9...ng_diagram.zip

^this is your best friend in cases like this, simply because it is so hard for other people to tell what and where your plugs and wires actually are for off of a single picture.

Also, fix that solder joint! Holy crap that is what happens when a soldering iron is not big enouph to warm the wire properly. Another note; make sure that all loose ends are are least taped over so they don't have the ability to short out. The cracked wire should be cut out and replaced. I would also remove the shrink wrap on those wires to see what other kinds of awesome solder joints are under there. I bet you it is going to be something simple, and far as I can tell the wiring could use a bit more attention to detail.

I personally have never had to work with the speedo readout, but I have worked alot with wiring. Start with getting everything properly connected, and then start shooting (ohm readings through the entire length of wire to check for opens and shorts) wires/sensors.

 

It sounds to me that you should check the ground on the UIM this is the ground for the entire instrument cluster, it will give you problems like you have described.

https://www.rx7club.com/showthread.p...ghlight=speedo

The reason the PFC is reading 0 right now is cause you have the gauge cluster out. The wiring for the speedometer goes from the sensor to the speedo to the ecu; with out the speedo, the ecu is in the dark.

 

I plugged the cluster back in and now I'm back at square one. The gauge cluster (speedometer) sits at 30mph while at idle. Ive checked the grounds at the UIM, PFC, and the battery. I can't figure it out. What should I try next? Also, I'm not sure if it has to do with the same thing but the A/C does not blow cold.

 

the wiring diagram is your friend.

check that all the grounds in the cluster are good, use an ohm meter referencing a good ground or preferably the negative terminal of the battery.

also check that the engine/uim has a good ground to the battery as well ( I doubt you will have a problem here cause the engine shouldn't run without a good ground )

after all that if you still don't find something wrong, check for a short in between any of the tach signal wires and the speedo signal wires coming from the speed sensor. It can be difficult to make sense of what you are seeing here so study the wiring diagram and maybe talk to an electrician or mechanic.

also does the speedo move with the tach when the engine revs? just curious.

good luck

 

Yes. The speedo revs with tach too. Do you think it could be the connections on the transmission by the speed sensor? Where do you suggest I should start?

 

I'm presuming its a 5 speed and would start with the transmission speed sensor and work my way through the wiring from that.

If you haven't already make sure your sensors (important ones) are in check through the commander.

 

So I figured out what the culprit is! Its the wires going into the PFC. I wiggled them around and now when I rev the car, instead of the speedometer going up (it sits at 20mph now) it goes down. Any suggestions?

 

you may have to rewire the connector, sounds like its not making a good connection.

 

which connector? The one going into the PFC? I will post a video tomorrow when I get home from work.

 

whichever one you wiggled that made it change

 

Might be a long shot to get and answer from the OP but I have the same problem. Speedo sits at 20 and goes down when I rev the car.

I just did a single turbo harness conversion bu did not touch any of the trans wires (to my knowledge. I saw mentioned above that the UIM ground is for those sensors, I will check that when I get home. Also IAT is not reading on my PFC so if that is the same ground I may have my problem solved.

 

So, I fixed it somewhat. Cleaned ground on UIM and it didnt work. Then I moved the ground to the firewall and made sure it was good. This fixed it to some extent. Speedo still goes to 20mph at idle every once in a while and give little blips when electrical loads are added, such as touching the brakes. It has to be the ground or interference feeding in through the splices I made months ago when I replaced the connector on the harness side. Wierd thing is it didnt do this before I removed the extra connectors from the harness.

Also got the IAT working but not the knock sensor

 

Took a step in another direction today, After messing with other wires (knock sensor & coolant level sensor) totally unrelated.

Car now sits at 20mph and Revs with the Tach, milage also goes up. This only begins after I let the clutch out and then nothing I do has an effect on it. PFC is also reading 28kph

Anyone have an idea? Im slightly loosing my mind.