2004 Dodge Ram 5.7L not responding to gas pedal

[thehandyman]

Hi,

So we have a work truck, a 5.7L Hemi, automatic, 2WD.

It was stalling, kind of intermittent, for a while. It didn't happen enough to really give us concern because it would just start right back up.

Well, recently the gas pedal just suddenly stopped working and the engine reverted to an idle. Pulling over, we would turn it off, turn the ignition on, fully lower the gas pedal, then raise it back up, turn the ignition off, then start it, and it would drive fine.

When it would stall or revert to idle with the gas pedal unresponsive, the red throttle body light would come on.

We replaced the throttle body- and that seemed to help for a while, but the issues came back. So, we replaced the bellcrank sensor, thinking there could be no other component or factor to the system that could remain...

Well, it still stalls, and the gas pedal becomes unresponsive, but now it happens so often we cannot drive the truck anymore.

Please, help us as this is our work truck and we are out of ideas.

 

[Redtruck-VA]

This certainly could be the APPS has failed. As for replacing the TB Bell Crank sensor I'm not understanding as the TB is sold as a unit and is not serviceable.
I would start by disconnecting the battery and after discharging the system, reconnect the battery and without touching the gas pedal turn the key to the ON position without starting the engine, wait 10 seconds, turn the ignition off. Then start normally.

 

[HemiSLT]

Well, the gas pedal (2 APPS sensors), wiring between the gas pedal and engine computer, wiring between the engine computer and throttle body, and the actual engine computer are also involved. You are going to have to find a really good technician at a dealer to figure this out unless you want to keep spending a lot of money.

 

[Redtruck-VA]

Curious you mention 2 APPS sensors, One on the pedal assy, where is the second sensor?

 

[HemiSLT]

There are two in the pedal assembly.

 

[Redtruck-VA]

I forgot about it having two signals.
Thanks,

 

[thehandyman]

Thank you for all of the replies.

There are two TPS sensors? A bellcrank sensor and something else?

I checked the obvious grounds, they are all tight and do not appear to be corroded. Visually inspected wires, which seem to be okay.

I told him to disconnect the battery, he did overnight, then ran the pedal up/down and ignition off/on, and it solved the problem for a few days... Then it came back.

He just now told me the vehicle stopped responding to the gas pedal about twelve times, including in the driveway. He said he thought it might not start again.

I heard mentioned that it has to be recalibrated with a special computer now that i changed the bellcrank sensor?

 

[thehandyman]

There are two in the pedal assembly.

I noticed that it had about seven pins. I thought perhaps it was some kind of digital rotary optical pulse generator and not a simple potentiometer. Is it two potentiometers, hence the many pins?

 

[Redtruck-VA]

The APPS has two outputs to the PCM. Then that drives the throttle motor control. The Electronic Throttle Control Module then feeds two TPS signals to the PCM as a feedback for positive throttle position. They use redundant signals for APPS and TPS signals to assure the throttle body doesn't lose signal. The Electronic Throttle Control Module is built into the Throttle Body and cannot be serviced.

 

[Redtruck-VA]

I noticed that it had about seven pins. I thought perhaps it was some kind of digital rotary optical pulse generator and not a simple potentiometer. Is it two potentiometers, hence the many pins?

It has six pins,
1. TPS
2. 5vdc
3. Electronic Throttle Control Module to PCM (+)
4. TPS
5. Electronic Throttle Control Module (-)
6. TPS (Return)

 

[thehandyman]

It has six pins,
1. TPS
2. 5vdc
3. Electronic Throttle Control Module to PCM (+)
4. TPS
5. Electronic Throttle Control Module (-)
6. TPS (Return)

Excellent information!

Can you tell me the procedure for testing it? Is it true a proprietary computer is needed to calibrate the APPS sensor to the throttle body mechanism? (Which was replaced and is new.)

 

[Redtruck-VA]

Excellent information!

Can you tell me the procedure for testing it? Is it true a proprietary computer is needed to calibrate the APPS sensor to the throttle body mechanism? (Which was replaced and is new.)

APPS calibration is easy as it gets.
1. Disconnect the battery
2. Discharge system anyway you like, wait a few minutes, turn ign. key to ON position.
3. Re-connect battery
4. Turn Ignition key to ON position without starting engine or touching the gas pedal and wait 10 seconds.
5. Turn ignition off.
6. Start engine.

 

[thehandyman]

APPS calibration is easy as it gets.
1. Disconnect the battery
2. Discharge system anyway you like, wait a few minutes, turn ign. key to ON position.
3. Re-connect battery
4. Turn Ignition key to ON position without starting engine or touching the gas pedal and wait 10 seconds.
5. Turn ignition off.
6. Start engine.

Alright, so we tried this. Waited for a while, connected the battery cables together (not on the battery of course) discharging any capacitors in the system with the ignition ON.

Reconnected the system, cycled the ignition, and drove it... Got about 500 feet before it did it again.

Red throttle body light, totally unresponsive to gas pedal, engine at high idle.

Turned ignition off, turned it back on, it was fine to get us home.

But that's all... He had to restart it twelve times to get home before I tried this.

Some things I have tried... I swapped the engine control relay in the fusebox with a fog lamp relay... No help.

Something strange, though, when it happened and the throttle body light came on, the interior lights came on. The back door was ajar, but it was strange the dome lights came on right after it stopped responding to the gas pedal. Indicating something wrong with the computer, or a short somewhere- or it could mean nothing at all.

 

[Redtruck-VA]

The good news is it is happening more often meaning a scanner should be able to pick it up. You can throw parts at it or have it scanned to hopefully nail it down.

 

[thehandyman]

The good news is it is happening more often meaning a scanner should be able to pick it up. You can throw parts at it or have it scanned to hopefully nail it down.

Autozone scan tool: No codes.

Scan tool I have: No codes.

Make sure the light was on before restarting it: Still no codes.

 

[Redtruck-VA]

I'm afraid you are going to need a diagnostic scanner from the dealer or better yet a good independent shop. Anyone with any ideas, pls post up...

 

[RonJon '06]

I just read a thread on DT where it ended up being a bad instrument cluster ($700). 2008 5.7L with no codes and constantly going into limp mode. Also maybe a bad battery or PCM?

 

[thehandyman]

I just read a thread on DT where it ended up being a bad instrument cluster ($700). 2008 5.7L with no codes and constantly going into limp mode. Also maybe a bad battery or PCM?

My buddy was telling me his Mitsubishi Eclipse doesn't start if the instrument cluster is disconnected. How strange. I used a digitizing oscilloscope to read the various connection on the APPS sensor connector.

FWIW, this is the Alldata pinout for the INLINE connector (Which is what I have) you probably gave me the stacked 6 pin connector (two rows of 3 pins):

1. APPS No. 2 Signal
2. 5 Volt supply
3. 5 Volt supply
4. APPS No. 2 Return
5. APPS No. 1 Signal
6. APPS No. 1 Return

I had trouble triggering the signal, but from what I saw, it changed linearly with no cutouts- meaning the sensor is probably fine.

Rick, the owner, says that he never noticed the red throttle body light coming on when he first turned the key. He said he never noticed it before, but now it's coming on. It goes off after a while... Or when he starts the truck. I think he's right, I never noticed it come on, either.

 

[Redtruck-VA]

All the various icons on the dash do a self test on startup and come on and then if there is no problem go off.

 

[tron67j]

2000 DODGE RAM VAN WAGON Service Manual SUPPLEMENT & DIAGNOSTICS Manual Set | eBay

These manuals will save you money in repairs/service. A must have if you own one of these vehicles.

www.ebay.com