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Electronic Throttle Body Problem - LSx

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Hey guys,

I've ran into a problem with an electronic throttle body on a supercharged LS7 engine last week on the dyno. Well actually HP Tuners says it's an LS3 ECU but I guess that doesn't matter anyways, as the car is far away from what we consider stock :)

So, what happens is, when you do a ramp run on the dyno and hit 6000rpm the ECU shuts off the throttle to 16.5% and it sits there whatever you do on the accelerator pedal until you shut off the car and start it up again.

This also happens on the street, not just the dyno ... and of course in about every gear you try that.

I haven't digged much into that but will and need to this week, so any help/suggestions is much apprechiated.

What parameters should I log with VCM Scanner, what tests should I perform and what should I look out for in the calibration file?

I have to say, that the car has been tuned previously by a different tuner and we've already had to ... well let's say, "better things up a bit" ... so I'm sure that part needs some attention too.

thanks a lot,


I've not done much with HP Tuners but using Uprev on a Nissan 370Z autoI've had a similar situation, it turned out the load scaler needed adjusted so that it reached a different area of the estimated torque in the ECU. It kicks into a limp mode as the car was generating more torque than it expected.

Thanks for the hint.

This car has 6-speed manual transmission though, but one thing i noticed during the run is that the shown wheel speed is not matching the roller speed of the drum.

It's way too high, so when the dyno shows 160kmh, VCM Scanner already shows 250kmh ... but then again, why would a speed limiter drive the DBW into, what feels like, fault mode?

Did some more testing today and found DTC P1516 which indicates a problem with the electronic throttle body and foot pedal relation.

It's explained in detail here: http://www.gearchatter.com/viewtopic9440.php

Anyways, the percentage relation between the FPS and the TPS is somewhat out of wack (see attachment).

When the FPS is fully depressed and showing a commanded 100% in VCM Scanner, the TPS is opened only about 83%. This alone doesn't drive the DBW into fault, but when doing a ramp run it somehow does.

Is there a procedure to calibrate TPS and FPS within HP Tuners?

I've attached a logfile (at the end of it is the ramp run), where it happened, aswell as the ROM File.

Also the Fuel System #1 Status displays OL-FAULT.

Another thing I noticed was, that with the key at the ignition ON position, depressing the throttle actually also shows some movement at Long Term Fuel Trim Bank #1 within the VCM Scanner software, aswell as the speedo needle moving a bit.

Could point to a wiring/ground issue?!

Attached Files

The TPS reading of 83% is actually normal (well typically this is 88% in my experience. The TPS PID actually represents TPS voltage as a percentage of 5.0 volts so at WOT the voltage ends up around 88% of 5.0 volts. There's a sticky on the HP Tuners forum covering it here: http://www.hptuners.com/forum/showthread.php?4961-2005-A4-GTO-Help-please&p=32069#post32069

If you log the ETC PID this will respond as you'd expect.

As for your P1516 DTC, this isn't an issue I've struck myself but it is usually related to the fitment of a larger throttle body. Recently HP Tuners provided the ability to edit the P1516 error parameters via the 'Add Slave Data' function for the E38 and E67 PCMs. There is a thread detailing this here:


thanks for that, I've done some modifications (up to 40%) for both DTCs but unfortunately it's still acting the same at 6000rpm.

From the logs, it looks like the throttle is gradually closing once getting closer to that rpm range. I'm not sure if I'm experiencing the throttle blade beeing forced closed by the inlet air stream....

We have small camera which we use to inspect the combustion chamber through the spark plug hole, maybe I can find a way to look on that throttle blade also... but then again, I still don't know if the electronics are forcing it closed or the air stream.

Frustrating to say at least...

Have you maxed out the torque limit tables? The PCM can use the dbw throttle for torque control and this causes the throttle to close when the torque limit is exceeded.

Again thanks for the hints ... the torque limit tables were all maxed out (even the reverse gear :) ).

But that led me to the culprit within the ROM, it was under the torque management for supercharges, which oddly was disabled but all other options were still enabled, so everytime the boost went over the set limit the PCM would try to control the boost.

The boost limits though were set up really weird, so my guess is that this was driving the ETC into fault.

Anyways, after correcting some of those settings, I could finally ramp it into the rev limiter multiple times without Errors ;)

thanks again!

great news, what did it make in the end up?

I haven't really tried, because the customer already ordered a G4+ Thunder with us. So I was just solving an issue for temporary vehicle use LOL :)

Last time I dynoed it with the DBW fault though, it made over 770whp and 900nm to the wheels. It was supposed to make just shy of 900whp and over 1000nm, but like a said ... different tuner and a whole different story. ;)

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