TPS readings strang
Thread Starter
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6th Gear
Joined: Dec 2025
Posts: 6
Likes: 0
TPS readings strang
There are a ton of great TPS threads on here and I hope someone could help with some strange readings I got through testing.
1994, f150, 302, E4OD
KOEO codes: 121 124
symptoms: shakey idle, wont shift out of first, will go to second if i put there on the shifter.
history: this thing has been pretty dang reliable, but i got a new car and it sat for a year. when it was parked it ran pretty well, no CEL, no major issues
well now i gotta get it running.
I took some readings from the TPS and this is what i got:
TPS readings:
key on engine off, warm
Red to batt neg: 5V
Green to batt pos: 4.5V
Black to batt neg:no reading
When unplugged the truck side connector shows
Red to batt neg: 5V
Green to batt pos: (battery voltage)
Before i tear of the throttle body, can anyone confirm this is a bad sensor and not something else?
Any other tests i should run before going replacement route?
Recommended brand for replacement?
1994, f150, 302, E4OD
KOEO codes: 121 124
symptoms: shakey idle, wont shift out of first, will go to second if i put there on the shifter.
history: this thing has been pretty dang reliable, but i got a new car and it sat for a year. when it was parked it ran pretty well, no CEL, no major issues
well now i gotta get it running.
I took some readings from the TPS and this is what i got:
TPS readings:
key on engine off, warm
Red to batt neg: 5V
Green to batt pos: 4.5V
Black to batt neg:no reading
When unplugged the truck side connector shows
Red to batt neg: 5V
Green to batt pos: (battery voltage)
Before i tear of the throttle body, can anyone confirm this is a bad sensor and not something else?
Any other tests i should run before going replacement route?
Recommended brand for replacement?
Fleet Mechanic
Joined: Nov 2022
Posts: 1,697
Likes: 416
To test the TPS, you need to probe the green wire (pos) and the black wire (neg) with a voltmeter. It should be .45-.9v at idle and 4.5-5v at WOT. It should transition smoothly as you move the throttle. (KOEO)
Black wire to orange wire should be 5v reference.
Black wire to orange wire should be 5v reference.
Last edited by Junktownbill99; Dec 7, 2025 at 07:45 PM.
Logistics Pro
Joined: Aug 2014
Posts: 3,558
Likes: 852
watch this video I posted. https://youtu.be/RMIJuOZrX3I?si=v5HfI4GD8ldD-VPx
Your video is with a DIESEL, not the same.
Cross-Country
Joined: Mar 2020
Posts: 79
Likes: 14
I was unaware that there would be a difference. Thks.
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Thread Starter
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6th Gear
Joined: Dec 2025
Posts: 6
Likes: 0
Here are the readings I got today
Key On Engine Off
TPS Connected, Probe inserted into back of the connector
TP SIG (black) to SIG RTN (green): 0V
SIG RTN (green) to SIG RF (red): 5V
TPS Disconnected
TPS side:
TP SIG (black) to SIG RTN (green): 60K OHMS upon rotating throttle variable changes but all in the XXK OHMS (i think the resistor inside the tps is blown)
Truck side
SIG RTN (green) to Batt Pos: 12V
SIG RF (red) to Batt Neg: 5V
Let me know what your thoughts are, I am leaning to resistor in the TPS being bad.
Key On Engine Off
TPS Connected, Probe inserted into back of the connector
TP SIG (black) to SIG RTN (green): 0V
SIG RTN (green) to SIG RF (red): 5V
TPS Disconnected
TPS side:
TP SIG (black) to SIG RTN (green): 60K OHMS upon rotating throttle variable changes but all in the XXK OHMS (i think the resistor inside the tps is blown)
Truck side
SIG RTN (green) to Batt Pos: 12V
SIG RF (red) to Batt Neg: 5V
Let me know what your thoughts are, I am leaning to resistor in the TPS being bad.
Last edited by Jack the Third; Dec 8, 2025 at 04:35 PM. Reason: mispoke