billy mild

I am in the process of hooking up my NX Express Window Switch. I used the white wire from the ECU in the passenger fender/footwell. When I did my setup with the engine not running and pedal to the floor I am only seeing 2.5v from TPS white wire. Idle shows 0.5v. Is this normal? Shouldn't it be 5.0v?

C5 Diag

Shouldn't your post be in the C4 Forum ???...says you have a '91 !!

Bill Curlee

There are TWO variable resistors in the TPS. Each is reversely proportional to the other

Each resistor has three wires. 5 VDC Ref, TP Sensor signal and a LOW Ref.

One resistor 5 VDC Ref is DK Green, TP Sensor Sig is DK Blue and the Low Ref is PPL

The other resistor is 5 VDC Ref yel/black stripe, TP Sensor Sig is Pink and the Low Ref is White

Your are on the LOW ref (Circuit ground)

Bill

billy mild

I had a C4ZR-1 up until last year when I wrecked at the track. RIP. I now have a C5 Z06.

billy mild

It sounds like I should still be okay since it does map properly to the TPS sensor. So is it normal to only have the range of 0.5 to 2.5v on that white wire?

billy mild

I'm tapping into the white wire off the of ECU in the passenger side footwell.

I have not done anything like this. I am working to hook up a NX Express window switch.

C5 Diag

That's the BCM !!!....TPS is on the throttle body !!...you are definitely in the wrong area Dude !!

billy mild

This is the computer that is in the passenger side fenderwell. It is the ECU trust me.

C5 Diag

First you said "FOOTWELL"...yes, the PCM is inside the passenger side "FENDERWELL" !!...I trust you Bro...with this window switch you are trying to install why are you testing the TPS Sensor ???????

billy mild

So I tapped into the White wire that goes to the PCM in the fenderwell. It it definitely tied to the TPS as it goes up and down voltage as I move the pedal. It maxes out at 2.5v which I was expecting 5.0v. Is getting only 2.5v max out of the white wire normal?

Bill Curlee

The white wire is a ground ref. Dont know what the needs of the window switch is but I would suspect it is looking for the actual TS signal circuit voltage

C5 Diag

Why are you checking TPS signal voltage at the PCM ????...you do it at the TPS sensor which is on the right hand side of the throttle body...it has 6 wires...the dark blue and the pink wires are your signal wires...the white wire is a "low reference" (ground) and it goes from the TPS to the TAC Module...whatever you are doing are you tapped into the TAC Module pin #10??...that's not the PCM my friend...I think you will have problems hooking up this NX Express window switch there...sorry but I can't help you any further...if I were you I have this thing professionally installed. I don't want to see you frying your TAC Module or PCM !!...good luck !!!

billy mild

I am tapped into the Dark Blue wire on the TAC module.

I made a mistake in my writing in the previous posts.