Truck Conversion & Toterhome Community - View Single Post

Pntyrmvr · 03-11-2024, 06:36 PM

The heart of the system that gets the accelerator pedal position information to the engine computer is an accelerator pedal position sensor (APPS).

These were mounted under the battery in the 2003 and 2004 Hemi trucks to convert the mechanical pedal motion into an electronic signal. Later trucks got a sensor built into the pedal.

The advantage for engine swaps like this one is that it allows the addition of another cable that gives pedal position info to the transmission through what is called a TV or throttle valve cable. The old school transmissions like A727 or A518 (used here) will burn up unless they match oil flow to throttle position.

In other words the box with the pedal sensor in it has another cable attached to the sensor that moves a lever on the transmission matching throttle position.

A box that ties the gas pedal, position sensor, and TV cable is available through the aftermarket, but I built my own to save money.

The APPS I had was used. On the 2250 mile drive I noticed a flat spot in the throttle where there was no change in engine tone. I hooked up my phone app to the OBD2 port on the engine computer and was able to monitor relative throttle position while driving. That confirmed a flat spot between 42% and 84% only on the way up, but smooth on the way down. Eventually the engine computer said no, too many out of spec throttle positions, and left me in the left lane of I-40 with no throttle. Luckily I coasted up an off ramp and pulled over.

The engine would idle so I left it running with the 4 way hazard lights on. I cleared all the road trip junk off the doghouse, put the dogs safely in their crates in the back, and pulled one bolt out of the doghouse. I hoped I had left my spare APPS on top of the engine next to the box with the operating one.

Pulling the doghouse off on the side of the road at night is a pain in the ass. After the first bolt was out I stopped and thought the situation through.

Even if the spare APPS was sitting on the motor I would have to clear the engine computer error codes to get it to work properly. Why not clear the codes now and see if the existing APPS would work. I cleared the codes, fired it up, and the throttle worked. I promised the gods of motor fuel acceleration I wouldn't go too deep into the gas pedal and we were off without pulling the doghouse.

She made it all the way to Arizona.

03-11-2024, 06:36 PM	#145
Pntyrmvr Senior Member Join Date: Mar 2019 Location: GTA Posts: 154	Sensor failure The heart of the system that gets the accelerator pedal position information to the engine computer is an accelerator pedal position sensor (APPS). These were mounted under the battery in the 2003 and 2004 Hemi trucks to convert the mechanical pedal motion into an electronic signal. Later trucks got a sensor built into the pedal. The advantage for engine swaps like this one is that it allows the addition of another cable that gives pedal position info to the transmission through what is called a TV or throttle valve cable. The old school transmissions like A727 or A518 (used here) will burn up unless they match oil flow to throttle position. In other words the box with the pedal sensor in it has another cable attached to the sensor that moves a lever on the transmission matching throttle position. A box that ties the gas pedal, position sensor, and TV cable is available through the aftermarket, but I built my own to save money. The APPS I had was used. On the 2250 mile drive I noticed a flat spot in the throttle where there was no change in engine tone. I hooked up my phone app to the OBD2 port on the engine computer and was able to monitor relative throttle position while driving. That confirmed a flat spot between 42% and 84% only on the way up, but smooth on the way down. Eventually the engine computer said no, too many out of spec throttle positions, and left me in the left lane of I-40 with no throttle. Luckily I coasted up an off ramp and pulled over. The engine would idle so I left it running with the 4 way hazard lights on. I cleared all the road trip junk off the doghouse, put the dogs safely in their crates in the back, and pulled one bolt out of the doghouse. I hoped I had left my spare APPS on top of the engine next to the box with the operating one. Pulling the doghouse off on the side of the road at night is a pain in the ass. After the first bolt was out I stopped and thought the situation through. Even if the spare APPS was sitting on the motor I would have to clear the engine computer error codes to get it to work properly. Why not clear the codes now and see if the existing APPS would work. I cleared the codes, fired it up, and the throttle worked. I promised the gods of motor fuel acceleration I wouldn't go too deep into the gas pedal and we were off without pulling the doghouse. She made it all the way to Arizona.