First off, I've "searched" my butt off and I still can't seem to find a potential solution so I thought I would just post up.

I'm helping a buddy work on his 1993 5.0L F150. Just for a background, we've recently replaced: plugs, wires, cap, rotor, fuel filter, checked/cleaned injectors, IAT, EGR sensor, some control module down on the side of the transmission (can't remember what the acronym is for it), it seems like one or two other sensors and the TPS.

Now the issue is, all the codes he was throwing are gone now except the damn TPS code (63 I think it is). It is a brand new TPS, I'm getting voltage in from the wiring harness and when back probing the wire from the sensor when it is plugged in it creeps up from ~0.5 volts to ~5.0 volts as the throttle blade is opened. So it seems to be functioning properly but it is still throwing the code and the truck still idles like crap (surges... dies sometimes) and part throttle application is rough at best.

Also, when we reset the codes we disconnected the battery for 30+ min, as some recommended, for the sake of clearing the memory in the ECM. And I don't think we have any vacuum leaks either.

Any suggestions as to what else could be causing this code to still trip and/or the truck to run like crap?

Thanks in advance,
Ryan

 

The PCM should display 3 digit codes in a 1993. There are a few exceptions, but I just wanted to point that out. If you have the proper TPS signal output as measured at the TPS with a meter then it is time to check the circuit back to the PCM itself.

The TPS signal is sent to the PCM on pin 47. The Signal Return is pin 46. Use this for reference from our friend Ryan at Ford Fuel Injection.cm - Truck Pinouts

 

It's possible I have the year wrong of his truck but all I know is I am connecting to the self-test port under the hood with an OBDI scanner tool that flashes/beeps and it keeps repeating code 63.

I will check the pins on the PCM. Thanks for the link/info. Where is the PCM located on this truck anyway?

 

The PCM is located on the driver's side of the cab behind the kick panel. It is accessed from the engine side of the firewall. This photo should help:



The inner fender can be removed after taking a few screws out. Makes it easier to get access.

 

Thanks again rla.

 

63 is low voltage from the TPS during self-test.
0.5 Volts is low if you taking the reading with a good DVM while using the return pin for ground. 5 Volts is a little high also it should be about 4.5 Volts at WOT.

Reference voltage should only be 5 Volts.

 

Good point there Bill. The closed throttle TPS voltage should be between 0.6VDC - 1.0 VDC. Anything less then 0.6VDC will trigger a low TPS voltage code.

For reference: Ford Fuel Injection » Throttle Position Sensor (TPS)

 

I'll go back and check again. If indeed it is reading less than 0.6V what might be the cause of this... just a wiring issue?

Thanks again,
Ryan

 

Bad TPS is my guess. Some versions of TPS sensors have a little bit of adjustment built into them. If so you could tweak it a little. Otherwise you are pretty much stuck with what you have.

Has this error just started or always been there?

 

Well the code has been there since I've been trying to help him with the truck but I don't know about before that. But the truck did use to run OK and then it started doing this choppy idle etc at some point.

 

OK, I re-checked the voltage tonight. My issue seems to be that with the throttle blade closed the voltage off the green wire only reads 0.04 volts until I open the blade probably 10% of the way and then the voltage jumps up to 0.8 volts and continues on smoothly from there until 4.97 volts. I "adjusted" the TPS around as much as I can without drilling the holes open more but I'm wondering if the new TPS I got just isn't bad. Any other suggestions before I go buy another new one?

Thanks again,
Ryan

 

You have a bad TPS.