TPS at 26% issue on B18

[kjlindgr]

Hey all. I've got an issue with my Hondata now that I didn't have before. I had the car all up and running great. Took it to the track and ripped off a 13.0 at 114mph with the new turbo setup. Hondata worked great!

I was having an issue with a BDL throttle body so I sent the TB back and they sent me a new one. I got it all installed and that good stuff and when I fired it up, the car raced at idle to like 5000 RPM. I was all WTF so I popped it on the laptop to see if I could figure out what it was doing.

I noticed right away that the TPS was reading 26% when the car was "on" but not running. I know it doesn't get an accurate reading unless the car is actually running so I started the car and no matter where the throttle is at, the TPS reading coming into the ECU stays at 26%.

So, I then took the TPS itself off of the TB and did some checking on that. It's getting 5v from the ECU, and has continuity at the ground. I checked the reference voltage coming out of it and that looks great too. It reads 0.019v when closed and 4.995v when fully open. Seems good to me.

I then traced the reference voltage wire back to make sure the ECU was seeing it. I have an OBD2 engine harness in the car with an OBD2-OBD1 conversion harness going into the P72 ECU. I can trace the refrence wire all the way back to where it physically plugs into the ECU so I know it's getting a signal all the way through the engine harness and through the jumper harness just fine.

I even went as far as putting another TPS on and still the same thing. The Hondata only sees 26% voltage reading no matter what. I was thinking about taking the ECU over to my friends house and putting it on his H22 to see if the TPS reading is any different but I haven't gotten to that point yet.

The thing that's stumping me is that nothing changed! I didn't change any wiring or anything and it was running perfect before I swapped the throttle body out.

Any suggestions? Is my ECU fried or something like that somehow? I can't imagine that being the issue since all the other Hondata features run just fine.

Thanks for the help guys...I'm stuck!!

[Hondata]

The ECU does not monitor the TPS with the engine off, so it will normally read 26% when not running. The problem is that if there is an error, then the ECU will also default to 26%. In this case you should see an error code for TPS.

Using a multimeter check voltage at the ECU between D11 and D22 (or D21). With the key on you should see around 0.5V with the throttle closed and 4.5 at full throttle. If there is a problem then trace the wires through the adapter to the TPS connector.

[kjlindgr]

Thanks for the response. The ECU is throwing a TPS code as soon as the engine starts up. I checked two different TPS sensors and both of them do the same thing so I'm pretty sure it's not that I have two bad TPS sensors. Plus, the reference voltage coming out of them is perfectly within spec.

Anyway, I'll measure the voltage across the pins and let you know what I find. Thanks!!

[kjlindgr]

I measured the voltages across these pins. At the plugs that plug into the ECU, I can read the refrerence voltage at pin D11. I think I'm having issues with the IACV which is causing some problems for me as well. I need to fix this issue.

A couple related questions though. How long does the car need to be running before the TPS reading on the Hondata starts reading? I've only had the car running for a few seconds at a time due to the "idle racing" issue which is IACV related. I'm not sure if this is a problem though as does throw a TPS code...unless it's related to an IACV issue.

[Spunkster]

As soon as the car starts, the TPS starts reading.

[kjlindgr]

Okay, for some reason now, the TPS is working, but the car is still freaking out. Not sure what's wrong here. I've got a graph here to (run2.jpg) to show what the car does now when I fire it up.

I plugged a P30 ECU into the car just to see how it'd react. It pretty much does the same thing leading me to think the the issue isn't in the ECU.

I've also got the map on the ECU attached as well just for reference if anyone cares.

I checked the voltage coming out of the GM 3-bar MAP and it's pretty good as well. 1.57V at atmospheric pressure. When the car starts up, it drops as it sees vacuum. I checked this because it looks like from the map that the sensor is getting a bad reading. But looking at the settings in the installed configuration, it looks fine. ???

Any other ideas?

[Spunkster]

Without a datalog showing the problem and a detailed description of the problem, it is impossible to speculate.

[Hondata]

Look at the MAP when you start the car - it seems to go up in pressure rather than down as the engine draws a vaccum. Look at the MAP parameters in your calibration.

[kjlindgr]

Look at the MAP when you start the car - it seems to go up in pressure rather than down as the engine draws a vaccum. Look at the MAP parameters in your calibration.

I noticed that too. That's what led me to test the voltage coming out of the MAP sensor. Things seem okay though on that end. I'll recheck the calibration parameters though. Thanks!

[kjlindgr]

Okay, I did more checking. I believe that the MAP settings are correct. At least they are the same as they were when the car was running perfectly fine before. But, now when the car is at idle, the MAP setting reads ~6PSI. No way this is correct.

I checked the voltage across pins D17 and D21 at idle thinking that my aftermarket MAP sensor took a poop on me. At atmospheric pressure (car not on) the voltage is 1.5V and at idle when the car sees vacuum, the voltage drops. I conclude that the ECU should be seeing a correct MAP setting.

So, I'm like 'eff this noise and I swap the aftermarket MAP sensor out for the stocker, pull the Hondata off and plug in a stock ECU. The car starts up and idles good...rich (440cc injectors), but good.

Next step, I keep the stock MAP sensor on there and put the Hondata back on and switch the setting from "aftermarket MAP" to "stock MAP". I try to start the car up and the Hondata reads ~25PSI!! Plus, it won't run for more than a split second before it dies out. My guess is because it thinks it's trying to compensate for 25PSI of fuel. The injector pulse graph confirms this as it's at 100%. I check voltage across the MAP pins and it looks within spec for the stock MAP.

Any suggestions on this? Could my Hondata have a more serious issue? What would it cost/take to get it sent in for a check by you guys to make sure it's not toast?

Thanks for your help guys!

[TurboGSR96]

Turn the key to the on position but dont start the car, attach your voltmeter to the TPS Sensor wires, mine has 3 of them, you will obviously need only 2. You have to rotate the TPS sensor until it reads .45v with the TB closed and 4.5v when you open it all the way. I thought I had a bad TPS after awhile but I had to get it right on .45v closed for the code to go away. It tends to move when you tighten it so make sure you check it after it is fully tightened.

[kjlindgr]

I don't get the TPS code anymore. Not sure why it just stopped showing up. Now, the TPS reads 0% at idle like it is supposed to...but the MAP reads ~6PSI!

[Spunkster]

Who socketed the ECU?

[kjlindgr]

Who socketed the ECU?

I did. It was working perfectly fine for about a month untill we swapped out the throttle body. Now things are a wee wacked up.

Do you think it's something that could have gotten fried?

[Spunkster]

It could be a socketing problem, but it is more likely something you did when swapping the throttle body. I would begin there and retrace your steps or even put it back to the way it was and see if the problem goes away.