I have a 99 F450 with the 7.3L in it. I brought it home the other day and parked it. Later I went to do something with it and I had no throttle response at all. I checked the wiring going in and coming out of the throttle position sensor. I have approx. 5 volts going in and the voltage sits at about .5 volts and rises as the accelerator is depressed on the outgoing wire. The other switch on the pedal is open and does close when the pedal is depressed, so it seems those are fine. I'm not sure what I'm supposed to have on the 3rd wire that goes to the TPS. If someone could help me with that I would appreciate it.


I have a Bully Dog tuner and it shows an exhaust back pressure sensor error and a couple of voltage errors to the accelerator pedal. I read somewhere that someone had an exhaust sensor short out and it starved the accelerator pedal from voltage or something like that but I do have good voltage at the pedal going in and out. I ordered a new sensor and tube but I don't have a lot of faith that this is going to fix it so I thought I would try to see if anyone had other suggestions.


If the exhaust pressure sensor was shorting out and I unhooked the wires could that make the pedal work if the sensor was the problem or would the accelerator pedal not work at all without that sensor being connected? (The old tube was somewhat plugged up and I saw it had a small rust hole in it)


If it's not the sensor, what else can I check? Where can I check under the hood to see if the wires from the TPS are getting power to where they need to? I assume they go to the computer and that tells the pump or whatever to give more fuel.


Any help would be appreciated greatly just in case the exhaust sensor doesn't solve the problem. I really need this truck back in operation as soon as possible so if anyone has ideas I'm all ears.

Thanks

 

You hadn't stated if you have an AT or MT.

Perhaps, with an AT, this could be your problem.....

No Pedal Response and /or No Gauges, or both:

Trucks with the 4R100 Automatic Transmissions (1999.5 -2003 MY) which present with a "No Accelerator Pedal accompanied by a No Gauge Activity".

Circuits: "N250, C212, 20140, 2135, 281a, and 220c" and Fuse #45 in the Under Dash Fuse Panel.

Most Probable Cause: Wire chafing in the steering column coat clutch on/off switch (Overdrive).

Repair: Remove Steering Shaft Decorative Coverings and inspect the wiring for chafing. Covering any exposed wiring with a suitable insulating product to prevent a reoccurrence.

Technical Service Bulletin

 

Sorry about that. Unfortunately, it has a manual transmission. Thanks for the reply though.

 

Don't worry about the exhaust back pressure sensor...that isn't causing your issue at the moment. The Accelerator Position Sensor has three wires....ground, VREF and signal wire. VREF should be 5 volts, the signal voltage will vary as the pedal is depressed and the last wire is ground to the PCM. The other switch is the Idle Validation switch. It has two wires.....12v power when key is on and the other wire is signal to the PCM.

If you can get your hands on a scan tool...then connect to the Idle Validation PID and see if it changes from 0 to 1 when the accelerator pedal is depressed. Also check the Accelerator Pedal position (read in percentage) and confirm the value changes when you depress the pedal. Don't worry about the actual numbers....just verify it changes substantially when the pedal is depressed. If I remember correctly, the percentage of accelerator pedal at rest is around 15% and 75% when mashed to the floor. If you don't see the PID values change, then inspect the connector and wiring to your sensors. From the sounds of your diagnostics so far, it appears that your APS and IVS are working properly so your issue might be in the wiring or connectors.

I hope this helps.

 

My dad had an issue with his 7.3 manual that was similar it ended up being the CPS(camshaft position sensor). Worth taking a look at, change it with a a known working CPS and see what happens. Just my .02.

 

I just checked the IVL wires and the contact closes when the pedal is depressed but I don't have 12 volts on it. Is that fused somewhere other than the fuse panels or does anyone know which one it would be? I did check all of the fuses in the dash and all of the small ones under the hood. Is there an inline fuse possibly? Thanks ARP2. I'll take a look at that sensor too if it still doesn't work when I get the 12 volts back to the IVL.

 

Fuse #19 / #29 Junction Box Fuse Relay Panel. Connector #244, Pin #2, RED w/ YELLOW Tracer

 

First of all, thank you to all of you for any suggestions. This has been very helpful. I'm not sure what happened or how it happened but I lost my 12v to the IVL switch. The fuse is good and it has power to it but it doesn't get to the switch located on the pedal. I pulled the connector off and had no voltage. I ran a jumper wire down to the switch from the fuse, started the truck, and I had my throttle back again. I would like to find the problem and fix it right but I'm not sure where to start other than take the dash out of the truck and start tracing the wire through the harness.


Once again, thank you to everyone for all the help. I greatly appreciate it and I can get my bucket truck back into service.

 

My bet would be at the Splice #213 or the connection at the fuse block.

Is everything else working on that circuit?

Check the wire for 12 v at the spice and the fuse block to see if you have power there.

 

Whereabouts would splice #213 be located? What's the best way to get to it and to get to the wire connection at the fuse block? I don't notice anything else that's not working on the truck.

 

By no means am I an expert, but in the image a few posts above, "S213" is where you have 8 wires coming together...