I need to test the tps on a 3800 v6 from a 2000 grand prix gt, what wires do I need to put the leads from my multimeter on to do a min/max voltage test? There's 3 wires, black (pin A) is low reference, Dark blue (pin B) is TP Sensor signal, and gray/black (pin C) is the 5 volt reference. According to alldata positive to signal wire, (pin B dark blue wire I'm assuming) and the negative to the tps ground which is where I'm confused. Is that the low reference wire (black pin A) or the 5 volt refrence wire (gray/black pin C)? It also says to drive the vehicle to duplicate the problem with the DVOM hooked up but can't I just turn the key to the on position and to a sweep from closed to WOT? I'm not sure if my meter leads are long enough to have it hooked up and drive. Anyone that has done this please let me know, I'd rather spend $50 for a tps than have to take it to a shop.

I don't know a TPS sensor works exactly but couldn't you hook one lead to 5 volt ref then the other to low refernce and check the ohms at different throttle postions? If not it would make sense to test the voltage on the low ref because you know the incoming voltage is 5 volts.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

ck03bluefire wrote:I need to test the tps on a 3800 v6 from a 2000 grand prix gt, what wires do I need to put the leads from my multimeter on to do a min/max voltage test? There's 3 wires, black (pin A) is low reference, Dark blue (pin B) is TP Sensor signal, and gray/black (pin C) is the 5 volt reference. According to alldata positive to signal wire, (pin B dark blue wire I'm assuming) and the negative to the tps ground which is where I'm confused. Is that the low reference wire (black pin A) or the 5 volt refrence wire (gray/black pin C)? It also says to drive the vehicle to duplicate the problem with the DVOM hooked up but can't I just turn the key to the on position and to a sweep from closed to WOT? I'm not sure if my meter leads are long enough to have it hooked up and drive. Anyone that has done this please let me know, I'd rather spend $50 for a tps than have to take it to a shop.

Black should be the sensor ground.
Your Grey/Black should be +5volt.

So if you put the meter leads there you should be getting around 5 volts, no matter where the throttle is.

Blue is the reference signal. Putting the meter leads on the blue and black will give you a real low voltage reading (or should). Should be under 1 volt. I think around .76 volts (give or take, they're rarely ever at that voltage). Then as you open the throttle further and further the voltage should go higher and higher. It should steadily increase with the throttle position and there shouldn't be any jumps. Yes you can do this by turning the key ON and opening the throttle.

I think doing it during a drive would be much easier to have a Scan tool so you can watch TPS position, rather than use a DMM.





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If what I read is correct, during a drive the fault happens too quick for the scan tool to read and not consistantly enough. Hopefully tomorrow after work I can hook up my meter and find out if it's a bad tps. Car wants to die when stopped at lights and intermittently dies driving. It also chuggs or hesitates at around 50 normally going up an on ramp. My first instinct was a "flat spot" in the tps. Fuel filter has been changed along with a recent tune up of plugs, wires, and serpentine belt and a cleaning of the MAF sensor and IAT sensor.

I'm doubting that the TPS is the problem.





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The only other thing that I can think of is a malfunctioning emergency fuel cutoff switch because when it dies you can turn the ignition off and it will restart just fine or a bad IAC valve. Have to figure this out as we're down to one properly running vehicle as my truck may have a cracked cylinder head or blown head gasket.

Kinda sounds like an issue we used to have with an old Plymouth van we had.. Fuel pump would cut on and off after it got hot.. never fixed the real problem.. just changed the fuel pump every month or so and it worked for a month or so.. Maybe its a faulty fuel pump.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

Ok here's what I got for voltages, .45v in closed position with key in on position. 4.17 volts at WOT with key in on position. 5.03v when testing the refrence voltage. With car idleing, voltage was the same .45v as when key was in on position. When I revved engine while running up to .75v it was smooth but dies as soon as I let off the throttle. Any ideas?

ck03bluefire wrote:The only other thing that I can think of is a malfunctioning emergency fuel cutoff switch because when it dies you can turn the ignition off and it will restart just fine or a bad IAC valve. Have to figure this out as we're down to one properly running vehicle as my truck may have a cracked cylinder head or blown head gasket.

Hmm......

You know, this almost sounds like it could be something related to oil pressure. Either the engine isn't having enough, OR the sending unit is bad. There's supposed to be a cutoff so that if the ECU doesn't see any oil pressure, then it will cut power to the fuel pump killing the engine. This is supposed to prevent damage to the engine. HOWEVER, the problem is that when your engine isn't running there's no oil pressure.... so it will allow you to re-start the engine.





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Talked with a friend and they suggested possible sticking egr valve, vacuum leak, crankshaft position sensor, or intake gasket leak. Going to take off the egr and clean it out at least and check for vacuum leaks too while I'm at it. Hopefully I'll get a good outcome otherwise it will be going to a shop to get fixed.

to test a TPS: get an ANALOG multimeter
Connect between signal wire and ground and make a smooth WOT move with the throttle. Look for it to be smooth as voltage rises. it should not drop out at all.


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Doesnt sound like a tps problem to me either. Last one I changed would surge at an idle but ran fine off idle.
Sticking egr usually causes missing at an idle or low 25mph cruising speeds.
I first thought MAF sensor , cause they are common problems but the symptoms dont match. For me MAF sensors cause loss of throttle response and intermittent shut downs. Tap on it while running to trigger a shutdown in most cases. You said that you cleaned it, did you try a different one?
You didnt seem to mention whether you have a check engine light on or not. That might be an important thing to mention.


01 cav w/01 3400 gam gt 4t45e

There isn't a check engine light on. With the car at idle it will run a little bit and then stall out. Took out the IAC and cleaned, it was very dirty and had an almost sludge on it. Broke the head off of one of the screws in the process of taking it out, thank you GM for putting thread lock on the screws. Re installed the IAC and still no improvement. Didn't even attempt to take the egr off and clean it because knowing my luck I would snap off another bolt.

One other thing I forgot to mention, ever since I replaced the fuel filter the gas gauge only works some of the time. Right after I was done, the first time and starting the car up the gauge went to full and there was only between 1/8 and 1/4 tank. Now it will go all the way to full intermittently when there isn't a full tank.

I would try tapping on the MAF sensor while running and see if it causes a stall. Or you could track down another one to try. No check engine light makes it a little harder to find the problem.


01 cav w/01 3400 gam gt 4t45e

Car is in the shop now so hopefully tomorrow I'll know what's going on with it.

Shop called today, only thing wrong is the fuel sending unit sensor that's messing up the gas gauge. Problem was the very very dirty IAC that I had cleaned which had a chunk of debris in the passageway yet that got pulled through after the mechanic drive it a little bit. I didn't spray the passageway with carb cleaner after brushing it out, if I had then it would have been fine. Shop still has to fix the screw I broke off though and fix the fuel sensor.

Quote:

Shop called today, only thing wrong is the fuel sending unit sensor that's messing up the gas gauge

My Grand Prix did that to me. Every time you parked on an incline the gas gauge would to up to F. I just left it like that, because it was something like 80 bucks for the new sender, and over 300 for the whole pump assy. I didn't want to replace the sender then have the pump go bad and then have to replace it again.

At least the problem wasn't anything major though.





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Still haveing the same issues with the car, every time it goes to the shop they can't get it to die on them, Got it back, drove for one day and then dies again. Went back to the shop, they couldn't replicate the problem again so we went and got the car, half mile down the road it dies. Took it back to the shop and got it to die while the mechanic was there, he thought the IAC wasn't adjusting quick enough so they kept the car, replaced the IAC with a new one from GM. They say they test drove it and it was fine, dropped car back off, took it to work, dies on the way there. I'm getting pretty pisssed by now so needless to say we're not taking it back to the original shop and now it's getting dropped off at dealership tonight to have them find the problem hopefully. So as of right now, $360 later and still not fixed correctly, about 5 days or so between all the time it's spent in the shop. Just plain frustrating at this point and it's probably something really stupid that's wrong with it that no one can seem to find.

intake plenum



my kill list:a geo metro and a mac semi wow did i kill that thing

Dealership called this morning, from the codes that they could pull it's sounding like a tps sensor. Funny, that's what I thought from the begining but must not show up on DVOM well enough because I had tested it already. We'll see how this turns out.

Shop replaced the tps sensor, MAF sensor plug. Took car home, dies almost at home. So now after approx $800 worth of work and still no answer I went outside and started messing around with plug to the MAF sensor and what do you know it runs just fine. So I wiggled it a bit more, runs like crap and dies. Turns out it's been a bad connection to the pins in the MAF and when the pcm loses that signal it shuts the engine down. Road vibration is just enough to wiggle the plug so it looses contact. Threw some dielectric grease in there so if it does wiggle out there should still be able to be an electrical connection. Hopefully this nightmare of a car is going to be gone monday and a new car will be replacing it. So the answer to the dealership and repairshop $800 question is bad connection to the MAF even with a new plug.