AFC Neo on RB25DET Issues

[totoro001]

Hey guys, installed my AFC Neo the other day and everything looks fine except I'm not getting a signal from the throttle cable. I was curious if their manual is incorrect as far as which whire to tap, or ir maybe it sounds more like my TPS is bunk/unplugged. Any Ideas?

[totoro001]

Just updating my thread as I do more testing in case someone runs across this issue in the future. On the ECU there are two different cables that are labeled for throttle position sensing. 38 (red/blue) and 48 (yellow/black). I didn't have my voltometer with me last night so I just tried splicing both and didn't get a reading with the AFC Neo on either. Tonight I'll remember to bring my voltometer home from work and see if either of them, or the TPS itself is sending out the signal and trace it back to where it's failing.

[eh?]

Tap pin 38

[totoro001]

Yeh I've tried that but it's not getting any signal at all. Going to trace it out tonight from the TPS back and see if it's shorted or something somewhere along the way.

[eh?]

Make sure you're getting voltage and a good ground to the TPS

[totoro001]

Allllllright.. Dug around with my voltometer tonight. It appears that when the TPS is plugged in, I'm getting nothing, however when I unplug it, from the ECU side I'm getting ~4.3v on the red/blue wire (#38). I'm guessing that my TPS is just bad. Going to take it apart (if I can) and fiddle with it tonight to see if it's shorting out or something.

On a side note, after fiddeling with the TPS, now magically my Wideband O2 sensor decided to just stop reading all together, and my hood won't latch shut. Totally unrelated, but I think this car is out to get me.
Modified by totoro001 at 8:16 AM 11/7/2008

[Darius]

Ummm sounds like your TPS is working perfectly. You SHOULD be getting 0V when the throttle is closed and ~4.3V when it's wide open. That is how the ECU determines the throttle position. It is a linear relationship between % open and voltage. Try checking that wire again with someone holding the throttle open or you pushing the gas pedal down.

[eh?]

It's actually supposed to read 0.4v-0.5v . The ecu needs to know this to determine whether to enter idle mode or not since the RB25 doesn't use a throttle switch like the RB20.That tps is adjustable, loosen the two screws and move the tps up or down to try and raise the voltage.

[totoro001]

Thanks for the input so far guys. Unfortunately no matter where I have the throttle (be it full close or full open) it still reads 0v when I have the TPS plugged in. I'm going to see if I can get my hands on another TPS locally.

[eh?]

Okay I'm confused.

With key on and the TPS disconnected:

At the the TPS sensor you should get

B/L- 0 volts- verify continuity to groundR/L- 0 voltsY/B- 5 volts

Plug back in the senor and check at R/L at make sure you have ~0.5v. Then at ecu pin 38 make sure you have the same voltage.

[totoro001]

Swung by a salvage lot near my office today and picked up a TPS from a J30 (which has the same part number as the one that came off my TB). We'll see if this one works. If not, than we can assume that the last owner of my motor/car put the wrong TPS on and it never worked.
Modified by totoro001 at 10:17 PM 11/7/2008

[totoro001]

Okay I'm confused.

With key on and the TPS disconnected:

At the the TPS sensor you should get

B/L- 0 volts- verify continuity to groundR/L- 0 voltsY/B- 5 volts

Plug back in the senor and check at R/L at make sure you have ~0.5v. Then at ecu pin 38 make sure you have the same voltage.

Ohhhkay, tried on the j30 TPS that I got from the salvage yard today and same symptoms. When it's unplugged I get the readings you have listed above, but when I have it plugged in, the R/L reads 0 (on or off throttle). I'm guessing that the J30 TPS just isn't compatible with the rb25 ECU. Could someone be so kind as to pop off your TPS and give me the part number off the back?

[eh?]

You've got wiring problems..

[johnny butt]

Q45 TPS will work for an RB25 s1 at least.

Maybe try that.

Also, I didn't see many differences from my KA TPS when I took it off.

[totoro001]

You've got wiring problems..

Went back out and tested this morning and here's what I've got. With the TPS unplugged and testing from the plug that (more or less) comes from the ECU I have:

Black: Good GroundRed: 4.3vYellow: 0.043v

Looks almost like my red and yellow are switched somewhere along the lines. Any thoughts?

[totoro001]

Ohhhhkay. Got a real live q45 TPS today, plugged it in, no love. So I eliminated the fact that my TPS was the issue. I clipped the 3 wires that go to my ECU from the TPS, and clipped the connector from the TPS, then ran temp wires right from the ECU to the TPS. After doing this, stuff started working. Narrowed it down to the yellow/black wire. Ran a new one and it seems to be working fine, though it's a little different from what everyone says. I'm getting 4.3v on the signal wire at 0 throttle, and then it drops down to like 1.2v at 100% throttle. I don't really care, it works and I can now tweak my AFC Neo. Thanks everyone!

[eh?]

swap your power and ground wires. You needs the right voltage to get proper idle.

[totoro001]

Alright, got bored and had a little bit of time tonight to fiddle with things. Switched the + and - around on the harness that plugs into the TPS (that'd be the yellow/black and black/blue) and now it's reading the right "direction". Off throttle it reads 0.3v, on throttle it climbs to 3.0v. I don't know why it's not reading 0.5 and 5.0, but at least it's heading in the right direction now. It also seems to start up and idle MUCH better now and it's not fighting my AFC like it was before.

[totoro001]

I think I'm going to find my car's neck, and choke it to death. I figured I'd go out tonight and give it a little "street tune" for both low and high throttle maps, and in the begening everything is going fantastically. Got the low throttle sitting right around 11.5 through about 5-6k rpms, so I slow down and run it through the gears pretty hard, then for about 2-3 miles it runs SUPER rich (like sputtering rich) at low throttle. I know I have an exhaust leak so I'm just going to say screw it, figure out where my exhaust leak is, then throw this thing on the dyno. I'm also fairly sure I have a boost leak due to some "creative" use of self tapping screws near the intercooler by the previous owner.

It wouldn't surprise me if the ECU was just jacked up overall, and if that's the case (which I should find out soon because I'm running out of stuff to replace) I'll just say forget it and drop in a PFC.