While I'm at idle, my speedometer sometimes sits at 20mph. I'm not sure what to check? Also, The odometer lights up most of the time with the lights turned off. When I turn the lights (headlights) on, the odometer screen turns off. When I bought my FD the previous owner has wires going to everything, so I'm not sure if something is interfering with the connection? I've searched for wires that could be interfering but I still don't see anything. Thanks...

 

Do you have a PFC?
My "other" speedometer did that when I had the PFC hooked. Someone here told me it's usually due to a bad ground.

 

I do have a PFC. Where was your bad ground located?

 

The PFC!

 

Does anyone have a wiring diagram for the PFC? It looks like it was grounded properly but there are a few wires that were hooked up to it and leading to nothing, so I disconnected them. Maybe I screwed something up.

 

There is a ground located in the passenger side kicker panel that grounds that part of the wiring harness to the ecu if rash is right that's where I would start. But I think the pfc will flash on start up and then go blank if it detects a bad ground because that's what mine did whenever I had a bad main motor ground. Just my two cents though.

 

It's grounded properly I think. It stays on. It's pissing me off though, lol

 

Thats the one I was talking about.

Managed to fixed it?

 

When and what were you doing to the car when this started happening?

 

I had this same problem, would read incorrect and sometimes not at all. Removed and and found a few components had failed. I would check for that kind of issue. This sounds like a higher percentage of the problem then a bad ground.

 

Its still not working right. When I purchased the car, their were wires for everything. After taking a lot of them out becasue they werent hooked up to anything, thats when I noticed it. So I dont know what to check? There were wires coming from the drivers side hooking into the wiring harness next to the PFC though. I'm pretty sure they werent hooked up to anything because I wouldnt have took them out. While I'm driving the speedometer will work most of the time but while its idling, it will sit at 20mph. Sometimes while I come to a stop it will sit at 0 and act normal.

 

When you install a powerfc there are several wires that need to be cut from the harness in order for it to work properly. So those wires could be the ones you found that weren't connected to anything.

Best guess is that while removing them you accidentally pulled one out that you weren't supposed to or loosened or shorted something.

My suggestion is to get the powerfc manual and verify the correct wires were cut. Then I'd download the cars wiring diagram and test the wires that send the speed signal.

 

Do you know where I can find the wiring diagram?

 

Probably in the fsm you can download it free online

 

http://www.wrex-racing.com/web/fd/info.htm

 

I've read a bunch of different threads and a few other people have had the same problem but no one said how they fixed it... I think it's something with the appeal wire. Which color is it by the PFC computer? There are some loose wires down there. Should I take a picture and post it?

 

Is this supposed to be connected to something?

Is this supposed to be connected to something?

Random plug not plugged in?

Theres a relay between the yellow and black wire. I think this is what I disconnected but I'm pretty sure it wasnt hooked up to anything.