Hi,
Why would I have no reading at the TPS.
Just fitted a new switch and when you try to set it up (o.55v) I believe, there is no indication of current, same as the old switch.
Car is still showing a code 22. It is an 86 IROC, 5.0ltr, TPI, auto.
Thanks in advance.

Alan.......

 

How are you checking it for voltage?

 

Hi mate,

3 jumper wires and putting a multi meter across terminals A & B.

Also there is about 5 volts coming from the grey wire that goes to the TPS plug.

Alan......

 

Hello Mate,
The 5 volts at the gray wire is correct, however if you are getting no voltage at all by probing pins "A" & "B" (black wire & blue wire). You might want to look at a broken wire somewhere or the possibility of a problem with the ECM.

 

Hi mate,

Just ran a wire from the ECM to the TPS, cutting out the original wiring. Same result !!

Looking like an ECM methinks !

Dont suppose you can recommend anywhere for a good second hand one as they are £345 over here in Scotland, UK !!
Think thats about $600 in your currency ??

Bummer !!

Alan.

 

Which wire did you run to the ECM, the black (pin "A") or the blue (pin "B") wire? Pin "A" is the ground wire to the ECM. Also and I know it is probably a dumb question, did you have the key in the "ON" position when you checked the voltage?

 

Hi,

Tried all three mate ! One at a time and yes, I did have the key in the on position !

Not a dumb question, as Electrics are not my scene, more of a body man myself !

Thanks for taking an interest and suggesting things to try.

Any other suggestions.
Alan.....

 

Check your e-mail mate!!!!!!!!!!!!!!

 

Cheers Trickster,
Very helpfull. Apoligise for the delay, but I was on holiday and had a death in the family, so been busy.
How ever, the latest is:
Code 22=TPS fault.
5v from grey wire, terminal C and 0.17 from blue and the black wire, terminals A & B.
New TPS fitted, still the exact same ??
Replaced the blue wire and the black wire from the ECM to the TPS in case there was a broken wire or a short.
Still the exact same.
Fitted a new ECM with my original blue PROM chip installed,
Still the exact same ???
Checked the ECM plug, especially terminals,C13 & C14.
Still showing a code 22 and still only 0.17v from A & B.

Sorry for dragging this out !

Am at a wee bit of a loss as what to check next ??

Any further suggestions would be much appreciated.

Cheers in advance,
Alan.............

 

Cheers Alan,

What year is your car and do you have the TBI or TPI 305 in your car.

 

Hi,

She is a 1986, 305 TPI, AUTO.

Alan.............

 

Alan, that TPS is adjustable and you should be able to get it with in proper tolerance by loosening the screws and moving it while measuring the voltage with the multimeter. I'm sure you're not doing this but I would like to mention it anyway, you do not need to have the engine running to do this test. Just have the key in the run position and don't overtighten the attaching screws. Also, do you have the meter set for the high or low end of the scale?

 

Yup,
Got the 2 torx screws loose so as I can move the sensor, and got the digital multi meter set to read up to 15 volts, with the increments set at 0.05 at a time !

Even more confused now.

When I move the sensor to about the middle position, I get no reading at all, but when I tilt the sensor right back it rises to 0.17 and wont go any further !

Alan.........

 

Alan,
Here is a picture of the throttle body and TPS. Do you have the lever on the throttle body that is circled in the picture resting on the lever of the TPS? Also try setting your meter at a range lower than 15 volts. one other thing I forgot to mention, make sure that the throttle lever moves freely and doesn't bind either.

 

Hi mate,
I actually took the throttle body off and gave it a good clean with carb cleaner to make sure there was no gunk in there so it is nice and free with no binding.

Throttle lever is resting on the TPS lever ok.

Set the multi meter as low as it will go.

Still the same ??

This is really a pain in the a**e !! lol.

Thanks for your help tho.

Could it be a fault in the PROM ??

Alan.........

 

would you like a trouble shooting diagram for the TPS circuit ?

 

I leave you with this-
Disconnect TPS and then disconnect battery and clear codes.

Key on engine off .. If Code 22 Resets - bad TPS circuit
Code 21 Now in memory. Bad TPS

 

Hi guys,

Tried all of the above, still the same !!!

Alan..............

 

Disconnected the tps. Cleared codes and with TPS unplugged still get 22.. with no 21 ?

If that is the case .. What is the voltage readings on each wire at the TPS connector. TPS unplugged, hooking the volt meter to the negative lead of the battery. All 3 wires.. Key on engine off ? Also positive lead of volt meter to the battery positive. probe the leads with the negative meter lead. What are the results... all 3

 

One way to check the TPS is to set the meter to read resistance.
Check terminals A & B (Blue and grey) with the throttle closed and then all the way open. Resistance should be the least at WOT. Post what readings you get.

Ben

 

I was looking at the piece I posted up there for you and realized... Carb'd.. woops. Sorry. This is what you need to find the cause

 

and this...

 

Ben,

Where did you get this info about setting the voltage on the TPS by checking for resistance? Does your info tell you what the correct resistance value is when it is set correctly? BTW, the ECM reads it as voltage at WOT. You can check the fuel sending unit by checking for resistance.

 

A TPS is a potentiometer which is really close to a variable resistor. Other than resistance, how else would you change the voltage? You could vary the amperage but electronics don't usually like that. If you have All Data or factory shop manual it will often have a resistance spec for the TPS.

 

That's interesting, while I must confess to not having ALDATA. I do however have all the GM service manuals for the camaros and firebirds for the years 1982 through 1992. I must say that in not one of them have I seen a reference to resistance values for the TPS. If you have this information available please post it here for others to see so we can use it for a reference.
BTW, fuel injectors are checked for servicability by using a resistance value.

 

I think GM just uses voltage for it's specs. I think it was Volvo I was working on that used a resistance spec.
You could calculate it though, what amperage do get at terminal C (5v reference).
Lets say it's .5 amp (no idea if that close). Lets you have .5v with closed throttle. 0.5v divided by .5 amp equals 1. So you would have 1 ohm of resistance at the TPS with closed throttle. Now lets say you have 4.5v at WOT, 4.5v divided by .5 amp equals 9.
So you would have 9 ohms at WOT on the TPS. The only trick is getting the amperage spec off of a properly working car.

Ohms law V/A=R

Ben

 

I am familiar with OHM's law and instead of trying to confuse everyone with all the math of trying to figure out unknown variables. Let's keep to the spec's listed in the service manual for third gen cars. It makes life simpler.

 

Okay. Just trying to suggest one other way of checking the TPS.
Didn't mean to try to confuse anyone, sorry.

Ben

 

This trouble shooting data is from Alldata. Not sure if he has a scanner but if not then a voltage test at the PCM would help to get the readings he is looking for.

 

Sorry to resurrect an old thread, but still got this problem.
1. New TPS fitted.
2. New ECM fitted. Using my original Eprom chip.
3.Blue, Black and Grey wire wires all replaced from the ECM to the TPS.
4. New plug on the ECM wiring loom fitted.
5. New plug on the TPS switch fitted.

Still only 0.17 volts read out from the TPS.
Getting this reading with 3 jumper wires connected, ign on and prodding between the black and grey wires.
Still getting 5.0 volts from the grey wire.

Inserted a small spacer, about 3mm thick between the throttle lever and the tang of the TPS, and this then gave me a voltage reading between 0.05 up to 0.70.
Set it at 0.54 and still a code 22 ??
Messed about a bit from 0.47 to 0.60 and no difference.
Disconnected the battery every time to erase the stored code.
Out of curiosity, re-fitted my old TPS, and the results were still the same !!!

Totally bewidered by this one ???

Any other suggestions ??

Alan.............

 

Im a little confused... is a scanner being used to look at the data or is this measurements at the pins with a dvom ?

 

No he doesn't have a scanner, only a DVM. If I might inject this wiring diagram here it might help with where the wires in that circuit go. Also Allen, if you will look at that chart that I sent you. One of the things that it mentioned was a faulty prom chip.

 

Start the car first, otherwise it might not start and do this...

Disconnect the TPS and Jump the Vref. ( 5volt wire ) DRK blue to ground.

positive of the DVOM to the dark blue lead at the PCM
Negative lead of the DVOM to the ECM body or metal case

DO YOU get 5 volts or close ?

If so its either a bad TPS ( even though new could be most probobal )

A bad connection causing a break down under load... Need a scanner to verify the PCM readings.

In this year PCM might have both a calibrator and a PROM. need to check and replace both if it has them if you replace these

 

Start the car first, otherwise it might not start and do this...

Disconnect the TPS and Jump the Vref. ( 5volt wire ) grey wire to the dark blue. The signal- dark blue them measure at the PCM

positive of the DVOM to the dark blue lead at the PCM
Negative lead of the DVOM to the ECM body or metal case

DO YOU get 5 volts or close ?

If so its either a bad TPS ( even though new could be most probobal )

A bad connection causing a break down under load... Need a scanner to verify the PCM readings.

In this year PCM might have both a calibrator and a PROM. need to check and replace both if it has them if you replace these

ALSO do you get high voltage code now ?

 

Just to corroborate, you MUST have 5V at the TPS as measured between the 5V reference line and the TPS ground. It should be within a few hundredths of a volt. Mine is something like +5.02V.