TPS Voltage

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Tonyrodz

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Took the Hoe back to the trans guy. I have no voltage at the tps. I wired in an after market pigtail. How can it run with 0.0 voltage? He thinks it might be the pigtail. IMAG2560.jpg
 

rockola1971

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Thats very odd. If the PCM didnt know where the Butterfly was (according to TPS feedback) then you would immediately go into reduced engine power mode and just idle. Im thinking that you all are looking in the wrong part of the menu of the scanner.
 
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Tonyrodz

Tonyrodz

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I'm pretty sure he knows how to work his scanner-no sarcasm intended-that's why I posted a pic of the screen. He said the same thing. He's never seen this before. He wiggled the pigtail around and the idle changed and it was reading voltage for a second. It now drives like a stock 4.8, no guts. Even the idle tone sounds different. Does anyone have a schematic /pinouts of the tps plug? I don't have a scanner but if like to see if my simple test lead detects voltage. I'm really fed up with this! Thx for any help.
 

rockola1971

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I dont know how the thing would even run out on the street if the PCM didnt know what the TPS position was. Again, it would go into reduced engine power mode. That is mandated in the PCM program when the TPS and Throttle Pot dont agree within a certain percentage. Both of those input into the TAC (Throttle Actuator Control). Its in between the Brake Booster and the Drivers side fender well on the firewall. Its a rectangular flat box.
If wiggling the pigtail causes the throttle to change then thats a tell tale sign that you have a broken wire. This is a classic failure of the DBW system. The replacement pigtail is usually about a foot long. The break usually is within 6" of the plug. The TPS is available with or without a pigtail and you can also get the pigtail by itself. Very easy to change out. Be forewarned that when you take off the vortec vanity top engine cover to be very careful not to get it up against the 2 heater hoses and push them around. You could break one of the coolant tees off up at the firewall. The molded in male fitting to the heater hose is usually the first to break and it doesnt take much pressure against them to do it. (ask me how I know).
Ill find a diagram. You can create a autozone account (free) and once logged in you can look at free wiring diagrams (same as the ones in the haynes manuals). Its a pain in the ass to find but its there.
 

rockola1971

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Ok I looked it up. Letters should be on the plug to show you what is what or just use wire color.

A - Grey 5v reference (source voltage) Should always be 5v (or real close) with engine running
B - Blk Low Reference
C - DK Green TP Sensor Signal 1 (this signal will vary upon position of butterfly/throttle actuator motor) should always be less than 5v.
D - LT BLU/BLK 5v reference (source voltage) Should always be 5v (or real close) with engine running.
E - Blk/Wht Low Reference
F - PPL TP Sensor Signal 2 (this signal will vary upon position of butterfly/throttle Actuator motor) Should always be less than 5v.
 
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Tonyrodz

Tonyrodz

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Thx. I'm lost in the sauce now, but I'm going to probe the dark green wire and see if it has any voltage. All I have is a simple test light. I priced out the tps pigtail at the dealer, my cost is $160, and it looks exactly like the pigtail I wired in already, except gm uses copper wire and the after market uses aluminium wire. Would that also make a difference?
 

rockola1971

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So if i understand you correctly, you already installed a replacement pigtail. Alum or copper, doesnt really matter. I suspect that your break is further away from you pigtail that you installed. You may just need to find the offending wire and replace a section or splice the break. Your 2002 have DBW?
Your test light is made for 12v. The tps voltage will be 5v or less. Your test light may not even light up even if 5v is there or will be very dim.
 

M1Gunner

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I'm pretty sure he knows how to work his scanner-no sarcasm intended-that's why I posted a pic of the screen. He said the same thing. He's never seen this before. He wiggled the pigtail around and the idle changed and it was reading voltage for a second. It now drives like a stock 4.8, no guts. Even the idle tone sounds different. Does anyone have a schematic /pinouts of the tps plug? I don't have a scanner but if like to see if my simple test lead detects voltage. I'm really fed up with this! Thx for any help.

Hopefully these will lend a hand Tony!

Here's the engine performance schematics. Check photo four at the bottom for the throttle bodys TPS pin out! Good luck boss!

IMG_3181.PNG

IMG_3182.PNG

IMG_3183.PNG

IMG_3184.PNG

IMG_3185.PNG
 
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Tonyrodz

Tonyrodz

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So if i understand you correctly, you already installed a replacement pigtail. Alum or copper, doesnt really matter. I suspect that your break is further away from you pigtail that you installed. You may just need to find the offending wire and replace a section or splice the break. Your 2002 have DBW?
Your test light is made for 12v. The tps voltage will be 5v or less. Your test light may not even light up even if 5v is there or will be very dim.
It's an 03, and it is dbw. I'm obviously over my head with this. I think I have a cheapy volts meter from hf. I wired in the pigtail because I kept getting the reduced engine power and it was fine until I got the trans done. Trans guy had to disconnect the battery, and he thinks it might have something to do with it. I'm lost! The butterfly opens all the way when pressing the pedal. IMAG2553.jpg
The truck wasn't running, but the key was turned and the pedal was pressed all the way down. It also revs when idling. Just curious --I had a remote start installed, think that could cause issues similar to what I'm experiencing?
 

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