detroitmuscle

Okay so i got my camswap and th400 swap and 9 inch rear swap done and everything figured out so the car is running and driving great. It does seem to run rich though and i have a mail tune from ion at madtuner with my svo 42lb injectors. The only code will throw intermittently is the throttle position circuit A high voltage code. I have changed the TPS and the pigtail but still the same problem. I have back checked it and it seems to flow perfect as i turn the throttle from 0-4.7 volts. When i give it WOT it pulls amazing but when i am just cruising through town at a steady rpm it seems to feel like the rpm's are floating a little. Like its not steady even though my foot never moves. Any ideas as to what to check next? Thanks in advance for the help.

bobdec

need year and model to verify.. also was it a A4 before going to TH400 . Thinking intermittent PCM reference ground may be opening or have noise on it. TPS gets 5 volts and a ground reference from PCM. You need the ground to drive the signal down (.4 to 4.5 volt swing). Three sensors use that ground, and it's not a chassis ground, it's a filtered ground from the PCM. Used by TPS, temp sensor in water pump and temp sensor in the A4 transmission.

detroitmuscle

Its a 97 SS car and yes it was an A4 before the swap. Where do you think I should start checking.

Injuneer

Have you checked the voltage between the gray 5V reference wire and the black ground wire, with the connector off the sensor?

Assuming you had P0123, the code sets when the signal voltage, blue wire to black, exceeds 4.9V for more than 1 second.

detroitmuscle

When i checked the voltage i got 5 volts to the sensor and then the rotation of the throttle was very smooth from 0-4.7 volts on the blue wire. The strait 5 volts came off the gray and the 0-4.7 came off the blue. I assumed this was the correct way to check it. Thanks for the input. Still lost.

bobdec

Here is a schematic, it's OBD1 so DTC and pins in the PCM are different , but the TPS circuit is the same. Fred asked if you put the volt meter negative lead on the black wire 'Sensor Ground" for your test. That's important since TPS high voltage can only be caused by two things, an open/defective sensor ground circuit. Or a short between +5 v reference and the sensor line, in the wiring from the PCM or internally in the TPS (which you have changed).

http://www.mifbody.com/DTCs/DTC%2021.jpg NOTE knowing electrical circuits this service manual diagram looks backward to me
the WOT and IDLE in the TPS are reversed, as shown WOT would put 0 volts on the sensor line and IDLE +5 which is incorrect. Otherwise it's OK.

I asked about your conversion because the sensor ground from the PCM goes to a temp sensor in the A4 transmission. A black wire on pin 'M' of the 4l60E connector. How did you disable this part of the harness, any chance of that line being shorted to another ?
TPS high is set by TPS voltage over 4.8 volts for 5 seconds, or voltage over 2.5 volts with air flow less the 10 afgs for 5 seconds, so a bad MAS would cause it, but you would also have a MAF DTC. . You voltage test said 0-4.7 volts, low voltage at closed throttle s/b between .3 and .9 volts is your TB aftermarket ? Ideally .45 to .75 is the actual operating closed TPS=0% range. I'm guessing at off the wall or intermittent problem causes here as this is a relatively simple 3 wire circuit. Twisting harness and connections with meter attached is another thing you could try, Maybe re-seating PCM connectors.. .

Injuneer

Sometimes they don't check what they put in the manual, particularly drawings. The online GM diagnostic charts for the 97 LT1 show that P0123 sets when TPS voltage exceeds 4.9V for 1 second. The test has to fail 90 times out of 100 samples.

And I've even found codes that I know exist, missing in some of the online GM diagnostic charts.

detroitmuscle

The only thing i can see is possibly a problem is that pcm grown on the tranny. I just left the existing tranny harness alone and just strapped it up and out of the way. Is there something i need to do with that ground?

GaryDoug

It might help to use a datalogging scan program on the TPS while you are driving. Vibration and/or elevated temperature can cause intermittent problems to arise even though the sensor looks ok while you are testing it.

I don't think the transmission ground has anything to do with this. The only reason they use a separate ground for the sensor is to avoid having any unnecessary current flowing through that wire that could affect the reading.

detroitmuscle

Okay, wired in my new gauges today and i found that at idle my temp just slowly creeps untill i finally shut it off at 220-230. Fans never turned on and on my tune they are set for 205-215. I then turned my ac on max and they still didnt turn on. I checked all relays with the foglight relay and they are all good. Then i checked the fans by running a jumper from D1 to +battery and one fan came on. Then ran same wire from F1 to battery and the othwr fan came on. What do ya think?

detroitmuscle

Okay, update. Changed the ecu water temp sensor pitail because the connector looked rough on the other one. Fans do kick on but my autometer gauge is saying they dont kick on till 220-225 or so. And it only drops down to 210 on the autometer gauge. Isnt this kind of high? They arent cheap gauges. They are the autometer pro comp ultra light electrical gauges. I mean, no its not actually "overheating" but on the factory gauge it would never get above 210. And both fans are kicking on at the same time like maybe they are skipping the low speed. What do you think?

GaryDoug

Both fans run on low speed and on high speed. They just get full voltage on high speed but only half voltage on low speed.

detroitmuscle

But isnt the fans not coming on till 225 a little high? And then it only dropping to 210 before climbing again a little high? Assuming of course that the autometer gauge is correct which it is supposed to be more accurate than stock.

Injuneer

Stock programming is both fans on low at 226*F, both fans on high as 235*F. GM designed the engine to run at the mid-point of the coolant temp gauge, which is 210*F. They do this to maximize fuel efficiency, while minimizing emissions. They aren't as concerned about power.

Where did you put the sensor for your AutoMeter coolant temp gauge?

detroitmuscle

On my sheet from ion at madtuner it says he set them for 205-215......i put the autometer sending unit where the factory one was in the side of the head. So assuming that my autometer gauge is correct and since my fans turn on properly it has to be possibly ion at madtuner not setting it lower like it says on the sheet???