ETCTP and ETCPP PIDs?

[DrX]

I've been experimenting with my stock 78mm TB and the 90mm LS2 TB. Looks like even the stock TB doesn't open to a full 100% so maybe this is what was intended.

I logged the 2 TPS PIDs and the 3 APPS PIDs. For both throttle bodies, all TPS values were always equal to all APPS values. I used the appropriate TAC modules for each TB. An 02 TAC module is used with the LS2 TB due to the TP sensors moving in opposite directions as in 02 TBs. My 04 TAC module was used with the 04 78mm TB.

According to the PIDs, the PCM is seeing values of 0-5V for all 5 sensors. All of which are always identical and all move in the same direction. But the various sensors are described as having differing output ranges and some of them even move in opposite directions. The ranges of the LS2 TB's sensors are even different from those of the 02 TB that is designed to mate with the 02 TAC module. So I dont see how the 02 TAC module would be able to transpose and synchronize the sensors values correctly. My 04 TAC module schematic says the input from the 3rd APP sensor is "not used." The 02 TAC module does use this input. But both logs show this sensor as active! Also, the communication between the TAC module and PCM is actually via serial data not analog sensor input.

Are these PIDs valid? They don't seem to be reporting what is actually going on with each individual sensor.

http://i114.photobucket.com/albums/n241/TDOC2004/TPSAPPS.jpg

[DrX]

Anybody else tried logging these PIDs? Do you see the same thing? Doesn't look like the PCM ever sees the actual sensor outputs.

[DrX]

OK, I can now scan what looks like actual sensor values. Just happened to read the release notes for V2(still waiting for mine) and saw that the ETC PIDs will only work in "General" scan mode. Appears to be the same with V1. So I guess that the PCM does see these.

Interesting that the various ETC sensor % values do not match the respective GM and SAE % values. i.e. the ETC % values all max out at only 39% when GM and SAE are at 100%.

http://i114.photobucket.com/albums/n241/TDOC2004/ETCPIDs.jpg

[DrX]

Even if these sensor values are passed along to the PCM, it doesn't look like they are processed there because an 04 PCM would not be happy to see the TPSensor values moving in opposite directions. The sensor ranges appear to behaving exactly as expected on a stock 02 78mm setup. So it would appear that the sensor output processing to convert to % TP is done in the TAC module and the PCM only uses the % values from the TAC module.

I just logged my stock 04 Trailblazer(5.3L) with a 78mm and both TPSensors move in the same direction with a range of 1V - 3.9V. All of the sensors still maxed out at 39% though. Maybe this is normal, or it could still be a logging issue? TPS1 and TPS2 voltage values are always identical.

Is there a simple electronic circuit that would convert the LS2 TPS2 signal so that it moves from 1V to 4V rather than 4V to 1V. i.e. so that it behaves the same as the TPS1 signal. Would this then allow the use of the stock TAC module(04 in my case) to avoid the other issues with this setup.

Electrical engineers?

I'm off to do some more logging with various setups on my truck.

edit: messed up the sensor ranges

[DrX]

Digging a little deeper now. Full sensor range on a 78 mm TB is from 0.5 to 4.2V. While the full range on a LS2 90mm is 0.5 to 4.5V. Both TAC modules(02 and 04) report 39.2% TP at 3.9V which the PCM interprets as 100%. After 3.9V the 39.2% wraps back to 0%. But the TAC system will not allow the TAC motor to move the blade past this point. 3.9V represents 92% of the 78mm's full range of travel(stop to stop), but only 85% of that of the 90mm. It looks like the 78mm TAC systems were designed to cease opening a little short of hitting the stop which leaves a 90mm using the same TAC module even a little more short of being fully open.

So it's not as simple as reversing the direction of the TPS2 output. Something would also have to be done to bring down the top end a little while leaving the minimum output alone.

[DrX]

Made some progress: http://www.performancetrucks.net/forums/showthread.php?p=3486916#post3486916