TPS Backwards
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Freshman User
Joined: Aug 2016
Posts: 39
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From: South Carolina
TPS Backwards
Hey all,
I've gotten alot of great help here before, not I have a new issue. I replaced my TPS on the new throttle body and am having issues calibrating this sensor. it is to my understanding that the TPS needs to be at ~0.95v at idle and ~4.6 at WOT. I'm not sure if this is accurate or not, but when I as doing my calibration, the readings were coming out backwards. At WOT, I was low and at idle I was high. Any help would be greatly appreciated.
I've gotten alot of great help here before, not I have a new issue. I replaced my TPS on the new throttle body and am having issues calibrating this sensor. it is to my understanding that the TPS needs to be at ~0.95v at idle and ~4.6 at WOT. I'm not sure if this is accurate or not, but when I as doing my calibration, the readings were coming out backwards. At WOT, I was low and at idle I was high. Any help would be greatly appreciated.
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Freshman User
Joined: Aug 2016
Posts: 39
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From: South Carolina
Mark, Thank you for that document. I was measuring the resistance correctly. Red is the 5v wire, green is ground, and black is signal. I back probed the red wire and the green wire to measure this voltage.
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Freshman User
Joined: Aug 2016
Posts: 39
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From: South Carolina
so, to dumb it down to my level 
back probe the black signal wire on the sensor to my black wire on my multimeter and the red voltage wire on the sensor to the red wire on my multimeter, and do not back probe the green ground wire on the sensor?
back probe the black signal wire on the sensor to my black wire on my multimeter and the red voltage wire on the sensor to the red wire on my multimeter, and do not back probe the green ground wire on the sensor?
Elder User
Joined: Sep 2012
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I'm not sure which TPS plug you have, but if you look in the PDF from earlier you can see which wire is TP and which is SIG_RTN. The plug has little details that will help you orient it to determine which wire is which. I also don't see the colors you've described on the wire diagram for 92-95... is your truck an 87 - 91?
At any rate, if probing red + green gives you backwards (high/closed low/open) measurements, I'd wager that red + black will give you the correct measurements (low/closed high/open).
It also doesn't matter which multimeter probe you use to backprobe... all that does is make your voltage measurement positive or negative but in this case that doesn't mean anything. All you need is the magnitude (numerical value without the sign).
At any rate, if probing red + green gives you backwards (high/closed low/open) measurements, I'd wager that red + black will give you the correct measurements (low/closed high/open).
It also doesn't matter which multimeter probe you use to backprobe... all that does is make your voltage measurement positive or negative but in this case that doesn't mean anything. All you need is the magnitude (numerical value without the sign).
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Freshman User
Joined: Aug 2016
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From: South Carolina
Mark, I have a 1993 F250 351W. The TPS looks exactly like the one in the document. I have the electrical and vacuum troubleshooting manual for the truck too. it describes these wires in it. I'll see what happens when I back probe the signal wire and see what happens. Stand by - and thank you for your help!
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Freshman User
Joined: Aug 2016
Posts: 39
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From: South Carolina
Mark,
I ran the test procedure and was able to "kind of" calibrate the TPS. HOWEVER, what I did was ground the multi-meter directly to the battery and probed the green wire (by all account this is the ground wire). I'm beginning ot think that this sensor is not wired properly direct from the manufacturer. I should be reading the redish/orangeish wire. Thoughts?
I ran the test procedure and was able to "kind of" calibrate the TPS. HOWEVER, what I did was ground the multi-meter directly to the battery and probed the green wire (by all account this is the ground wire). I'm beginning ot think that this sensor is not wired properly direct from the manufacturer. I should be reading the redish/orangeish wire. Thoughts?
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Fleet Owner
Joined: Oct 2005
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From: Kentucky
There is no calibration required for the TPS. Anything between 06 to 1.0V is within specification. Try to adjust it to a certain value is pointless. It's an urban myth to adjust it in that manner on these trucks.
If you have a Motorocraft TPS the wire colors and functions are here:
Motorcraft TPS Wire Colors
VREF - Orange
TP SIG - Green (TP=Throttle Position SIG=Signal)
SIG RTN - Black
If you have a Motorocraft TPS the wire colors and functions are here:
Motorcraft TPS Wire Colors
VREF - Orange
TP SIG - Green (TP=Throttle Position SIG=Signal)
SIG RTN - Black
Elder User
Joined: Sep 2012
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You don't have to calibrate it... just put it on and plug it in. The only "calibration" per se would be clocking it if you've messed with the throttle stop screw -- even then it would most likely still be in range.
You do not test the TPS output against ground -- the circuit is NOT a grounded circuit in ways that matter to you. The computer reads the voltage differential between TP_SIG and SIG_RTN and both of those have voltage on them. You must test TPS signal by measuring voltage between TP_SIG and SIG_RTN.
It is highly unlikely that it came backwards from the manufacturer.
Have you tried running the truck with the new sensor? That's what I would do.
You do not test the TPS output against ground -- the circuit is NOT a grounded circuit in ways that matter to you. The computer reads the voltage differential between TP_SIG and SIG_RTN and both of those have voltage on them. You must test TPS signal by measuring voltage between TP_SIG and SIG_RTN.
It is highly unlikely that it came backwards from the manufacturer.
Have you tried running the truck with the new sensor? That's what I would do.
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Freshman User
Joined: Aug 2016
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From: South Carolina
Gents, I believe I am tracking. The simple fix to the low voltage would have been to adjust the idle screw on the top of the throttle body? I bought a newer, bigger throttle body and the screw was all the way closed. However, I did crank the truck and noticed an imediate improvement at the startup - no more sputtering.
FYI: This issue was only a small part of the overall wiring harness issues I was having. Other EEC-IV codes I have pulled are 114 (ACT), 116 (ECT), 327 (EVP), 565 (CANP), 636 (Trans Oil Temp sensor). :|
FYI: This issue was only a small part of the overall wiring harness issues I was having. Other EEC-IV codes I have pulled are 114 (ACT), 116 (ECT), 327 (EVP), 565 (CANP), 636 (Trans Oil Temp sensor). :|
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Codes 114, 116 and 636 are typically triggered if you did not warm up the vehicle sufficiently before running the tests.
Hotshot
Joined: Jun 2015
Posts: 12,876
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Gents, I believe I am tracking. The simple fix to the low voltage would have been to adjust the idle screw on the top of the throttle body? I bought a newer, bigger throttle body and the screw was all the way closed. However, I did crank the truck and noticed an imediate improvement at the startup - no more sputtering.
FYI: This issue was only a small part of the overall wiring harness issues I was having. Other EEC-IV codes I have pulled are 114 (ACT), 116 (ECT), 327 (EVP), 565 (CANP), 636 (Trans Oil Temp sensor). :|
FYI: This issue was only a small part of the overall wiring harness issues I was having. Other EEC-IV codes I have pulled are 114 (ACT), 116 (ECT), 327 (EVP), 565 (CANP), 636 (Trans Oil Temp sensor). :|
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Freshman User
Joined: Aug 2016
Posts: 39
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From: South Carolina
Thank you for posting those BBK directions. Looks like my ignorance got in the way of my reading comprehension and I followed them up until Step 8 - I was too eager to find out what power changes the 61mm TB would add to my first engine rebuild. I'll do this tonight with hopes that it will solve the issue. You know, sometimes the most obvious solutions are those right in front of us. Thanks for the reminder!
As far as how the TPS is doing now - it seems to have fixed a few issues. The truck is no longer throwing the voltage code and I'm running much leaner now whereas before I was driving to and from the store, and coming home smelling like a gas can.
As far as how the TPS is doing now - it seems to have fixed a few issues. The truck is no longer throwing the voltage code and I'm running much leaner now whereas before I was driving to and from the store, and coming home smelling like a gas can.
Hotshot
Joined: Jun 2015
Posts: 12,876
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How much power above stock did you go? Wondering why you went with the twin 61 as opposed to the twin 56? I put the twin 61 on my 392. I had a shop gasket match the Edelbrock upper to match the larger throttle body.