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avfordguy · 04-15-2022, 02:12 PM

I would hang my hat on wire issue from pcm to electronic throttle body, possible rodent damage. Ford uses a "fail safe redundant" circuit to control the etb, has 3 circuits if one fails it just turns the wrench light on, if dead pedal 2 circuits have been damaged.
Forscan is your friend!

tetranz · 04-15-2022, 02:52 PM

Quote:

Originally Posted by avfordguy

I would hang my hat on wire issue from pcm to electronic throttle body, possible rodent damage. Ford uses a "fail safe redundant" circuit to control the etb, has 3 circuits if one fails it just turns the wrench light on, if dead pedal 2 circuits have been damaged.
Forscan is your friend!

Yep, that what I'm hoping for. Although it seems weird that a rodent or something would have chewed through two but ... you never know.

I ended up getting one of these: https://www.amazon.com/dp/B07Q6HWY6C

I looked at Forscan. Maybe I should have got that and saved myself some money but I was a bit put off by talk on their page about Russian sanctions etc. I guess that only applies to the paid version. I kind of prefer a dedicated device anyway.

tetranz · 04-17-2022, 11:41 AM

I was there yesterday and the codes are:

P0122 which is "Throttle /Petal Position Sensor/Switch A Circuit Low Voltage" and
P0222 which is the same for B.

I couldn't find anything that looked like a chewed cable. I don't know if it's the position sensor on the pedal or the throttle body or something in between.

I think I'm going to get someone to look at it. I'm sure if I had easy access (not a 80 mile drive) and plenty of time, I could probably fix it but my attempts at following some YouTube videos leave me more confused as to what's what so I'm getting a little out of my depth and comfit zone.

I could replace the sensor on the pedal easy enough and they only cost about $30 but one part of the live data stream shows a percentage going up and down as I press the pedal which suggests maybe it's not that.

I found a small car repair shop not far away, Google reviews look good if that means anything, including one reviewer who was happy with their service on an RV so I think I'll give them a call tomorrow. As I understand it, the throttle system is basically the same for Ford cars and trucks so someone experienced on cars should be able to handle it.

tetranz · 05-01-2022, 10:00 PM

I still haven't resolved this unfortunately. I was back there today for another look.

I don't see any evidence of wiring damage by rodent etc. The pedal looks good. I pulled the connector out of the pedal. It looks clean and tidy.

I disconnected the cable from the throttle position sensor. It has four pins. One of them, presumably the power / reference source has 5 volts to ground. Voltage is going in, the fault code says low voltage coming out of the TPS. It's looking to me like the TPS is faulty. I'm happy to be convinced otherwise but it seems like a good place to start.

The TPS is one of these https://parts.ford.com/shop/en/us/el...ttle-7876387-1 which I can get easy enough. It looks like an easy thing to replace until I start reading about the loctite on the screws and the need for heat. I've found multiple posts online warning that without heat there's a good chance of breaking the head off the screws. One video showed heating the screws with a blowtorch. That was with the throttle body out of the vehicle. I assume that would be very foolish idea in the vehicle anywhere near gasoline so I won't do that. Some suggest using a soldering iron. Some report trying that and failing but I think they're trying with a small iron designed for small electronics. I have a soldering gun which I suspect has enough thermal power to heat up the screws. Any other suggestions for heating or generally removing the screws? It's the blue loctite which is apparently nowhere near as "permanent" as the red. I want to avoid removing the throttle body if possible but I'll be in a real pickle if I break a screw. The deeper I get into pulling things apart the further I get from my comfit level and a feeling of "I really shouldn't be doing this".

If anyone can recommend anyone in East Texas I'd be happy to hear from them. It's near Corrigan which is between Livingston and Lufkin, a bit over an hour from the north side of Houston. I've made contact with a local car repair guy. He seems a nice enough guy and is wiling to take a look but he doesn't seem to be interested in any sort of diagnostic troubleshooting. He wants to leap straight to replacing the accelerator pedal and throttle body and no talk of doing some simple voltage measurements like I have now done myself.

tetranz · 05-08-2022, 08:16 AM

I was there yesterday. I haven't really made much progress but I do have more information. A helpful person on a Ford truck forum gave me some pages from a service manual and a schematic diagram.

I was reading the wrong pins on the throttle position sensor. Now I have pinout information, it appears that there is no reference voltage going into the TPS.

I'm kind of stuck as to what to do now. The cable from the TPS merges into a much bigger wiring harness and who knows where it goes after that. The obvious thing would be to check if there is voltage coming out of the PCM computer unit. The service manual mentions a "Pinpoint test C" but I don't know where or what that is.

I'm actively looking for some professional help but that's easier said than done where it is. I notice the Ford dealer about 25 miles away does mention "mobile service" on their web site so I might see if they're interested in helping.

HarryStone · 05-08-2022, 08:57 AM

I'd suggest you invest in one of these manuals. They are computer based and easy to use.
https://www.ebay.com/sch/i.html?_fro...anual&_sacat=0

THenne1713 · 05-09-2022, 12:48 AM

(Someone correct me if wrong) but I believe I read most modern sensors & devices (e.g. injectors, etc) feed constant 12v to the sensor or device, then the computer controls the ground, or (for sensors) reads the ground side? If So, for TROUBLESHOOTING, tap a 12v source and feed it to proper pin on TPS and see if it helps?

tetranz · 05-09-2022, 11:10 AM

Quote:

Originally Posted by THenne1713

(Someone correct me if wrong) but I believe I read most modern sensors & devices (e.g. injectors, etc) feed constant 12v to the sensor or device, then the computer controls the ground, or (for sensors) reads the ground side? If So, for TROUBLESHOOTING, tap a 12v source and feed it to proper pin on TPS and see if it helps?

This one is definitely supposed to be 5 volts. The throttle position sensor is a four wire device. Reference, ground and two signal lines. The signal lines operate in reverse. One goes 0 to 5 and the other goes 5 to 0 when the throttle opens.

That said, you have given me an idea. If the problem is just that the 5 volt reference voltage is not there but everything else is good then I wonder how crazy or dangerous it would be to do what you're saying but with a 5 volt source. I'm into electronics so that is something I could arrange with a three terminal regulator to produce 5 volts. It would just be to drive it enough to get to a service center.

THenne1713 · 05-09-2022, 11:09 PM

If not a wire issue, (TPS to Computer?), then sounds like problem in computer? They may feed that 5v by a resistor in the ground side of TPS on circuit board dropping the other 7v+ in the resistor. BAD WIRE Plug CONNECTORS/ CORROSION also strong possibilities, if not rodent damaged wires? There are also some online (FREE) Ford Truck websites with sharp mechanics that may have better/BEST advice? Then there are also Online FORD PAID MECHANIC ADVISE websites; (been to them, but never needed the paid advice myself)

tetranz · 05-10-2022, 07:46 AM

Quote:

Originally Posted by THenne1713

If not a wire issue, (TPS to Computer?), then sounds like problem in computer? They may feed that 5v by a resistor in the ground side of TPS on circuit board dropping the other 7v+ in the resistor. BAD WIRE Plug CONNECTORS/ CORROSION also strong possibilities, if not rodent damaged wires? There are also some online (FREE) Ford Truck websites with sharp mechanics that may have better/BEST advice? Then there are also Online FORD PAID MECHANIC ADVISE websites; (been to them, but never needed the paid advice myself)

Yeah that all makes good sense about corroded connectors etc. My main problem is not knowing my way around it. It even took me a while to find the TPS

.

I have started a thread on a Ford truck site. https://www.ford-trucks.com/forums/1...l#post20387664 where I've received some good information. I haven't thought of paying for online help. I think I just need to make a bigger effort to find someone locally or close enough.

I don't think it would be a resistor reducing the 12 to 5 volts. It's a precise reference voltage so I think it's much more likely to be a voltage regulator.

swampdog2 · 05-10-2022, 08:08 AM

I had the same problem on 2005 ,long story short after a week of testing and replacing ! I ended up replacing throtle body cost was 238.00 from Orileys auto parts ! Runs great not a big job did it myself !

tetranz · 05-15-2022, 05:18 PM

Quote:

Originally Posted by avfordguy

I would hang my hat on wire issue from pcm to electronic throttle body, possible rodent damage. Ford uses a "fail safe redundant" circuit to control the etb, has 3 circuits if one fails it just turns the wrench light on, if dead pedal 2 circuits have been damaged.
Forscan is your friend!

You were right

I should have found it earlier but it was in a hard to see place and not so obvious with the covering still mostly around it. I found it by feel with my arm deep in the engine. I haven't fixed it properly yet but I joined it with some alligator clips and engine is working perfectly now. That yellow wire is the TPS reference.

I think I'll have to find it a new home. Too many rodents.