I have a 2009 E350 12 passenger van with the 5.4 engine. I've had intermittent TPS issues over the years and even had the entire throttle body replaced about 4 years ago.


The problem now is that the engine will suddenly go into limp mode, with the "wrench" light coming on. The code says a TPS issue. For a couple of years, I could disconnect the negative battery terminal and discharge the system, thus doing a "reset" on the computer and that would fix the problem, sometimes for over a year without having a single issue. But now the reset no longer works and the van goes into limp mode as soon as it starts to re-calibrate idle speed. Last night we got stranded on a lonely road, an hour from home, in a thunderstorm. Fun.


My question is, before I replace a TPS, which is more likely to be the culprit, the TPS on the throttle body or the one on the accelerator pedal?
Both are expensive, even for DIY, so I would hate to guess wrong.


Thanks for any help on this.

 

Hi KAP,
Right off the bat, there's an old saying in the repair field,
"Test don't Guess".
With the drive by wire systems such as in your vehicle there are several safeguards to prevent the engine run away effect. When the system is working correctly, which it is , limp mode is to protect you and everybody else on the road because there is something going on with the system that needs to be corrected.
Worn throttle body components, dirty throttle plate/bore, conflicting signals from the accelerator pedal sensor and the sensor on the throttle body, intermittent connections and of course PCM updating all get into the picture. To try to diagnose the problem over the internet would be not very smart! An experienced tech with the right equip ( graphing meter/scan tool) should be considered to determine the exact cause of the incorrect info getting to the PCM. It could involve any of the earlier mentioned reasons and probably a few more. As you know there is nothing like replacing perfectly good parts and the problem still exists, plus it gets expensive too!

 

Thanks for the info. One other question, I've noticed that this problem with the TPS seems to coincide with a low battery/battery in need of replacement, over the years.


Is there any way that a low voltage issue could cause the throttle position sensor to start going haywire?


Thanks.

 

As you are probably aware, any low voltage condition can cause problems especially when we are dealing with millivolts. It wouldn't be the first time a battery problem caused some seemingly unrelated problem. Here again, if you suspect a problem there, get out your trusty multimeter and try a few checks. Sometimes we stumble upon the problem and other times we need to play detective and search it out. To just suggest you replace any parts without being relatively sure they are either malfunctioning or just plain defective, to me , is just plain misleading, and it does get expensive.
If you feel the battery is questionable , just have it tested . At least that would provide some piece of mind and allow you to check other possibilities.

Do you recall what the code was that it had?

 

My original code was a P2111, Throttle Actuator Control System - Stuck Open.


I replaced the TPS and no change. I then replaced the throttle body with a used one and again, no change.


I then replaced the accelerator pedal and sensor with a used one and no change still.


So finally I took it to the Ford dealership since I figured that they would be able to at least diagnose what the true problem was and then I could decide what to do about it.


Turns out I had two places where the wiring harness had become old and brittle and when the engine temp reached a certain level, the wires would droop just enough to short the voltage going to the throttle body TPS and/or actuator motor. Finally the wires reached the point where the voltage was permanently interrupted and thus leaving the engine to cool overnight no longer did the trick.


Ford charged me a $135 electrical tracing fee and $150 repair fee including parts and labor. Grand total was right at $300.00.


Although I spent $150 trying used parts on my own, it saved me money because I could at least tell Ford what WAS NOT the problem, allowing them to assume an electrical issue, which it was. Plus, I can sell my used parts on eBay and make my money back.


Thanks for the help and advice.