Engine/Transmission (1998.5 - 2002) APPS cause high idle?

[CJ Lagos]

My truck recently had an 0122 code. I have had no more than 2 dead pedal/hesitations over the past few months. I put a multimeter on the apps voltage wire and mine is @ . 44v @ idle. I cycled the pedal a few times and the voltage smoothly went up and down.



I drove the truck to autozone so I could clear the 0122 and get rid of the check engine light. As I got back home, I noticed the idle was way up(1000-1200rpm). I could blip the throttle and the truck would rev like normal but would return to the high idle condition. It seemed to idle smoothly - just high.



While it was idling high, I put my multimeter back on the voltage wire and saw . 44v again. I was hoping to see a higher voltage and prove the apps was the culprit.



Can the APPS cause high idle if it still thinks the pedal isn't pressed If not, what else could cause that?



No new codes.

 

[Marco]

What else could cause that?

The APPS ground wire. No ( or poor ) APPS ground = High idle @ 1000-1200 Rpm.



Marco

 

[CJ Lagos]

Hi Marco - thanks for the reply. I looked at the wiring coming out of the apps and it just goes into the main engine harness. There is a large guage ground wire running directly to the PDC and there is a pair of wires that run back behind the timing cover, can't see where they plug in. I'm not sure if these are grounds or not.



Any advice on where to check the ground, is it in the apps connector itself or elsewhere?

 

[Marco]

Yup, the APPS ground goes into the engine harness. I think it's pin 11 on the ECM... several grounds are tied together in the engine harness and then directed to pin 11.



Marco

 

[Marco]

Lookie here:

http://www.dodgeram.org/tech/dsl/ECM/ecm.gif



Marco

 

[CJ Lagos]

That diagram is great!



If the ground is lost, can the computer still read the apps voltage or is that the problem? With my multimeter I grounded the common side to chassis which would explain why I could see the . 44v reading. Maybe the computer couldn't... could this be the cause of 0122 engine code? Without a ground there was no signal so the computer reported a low voltage?



I would think that if there was a problem in this circuit I would see problems with all the other sensors sharing the same ground. Perhaps just the "last mile" of the wiring is the problem. With the APPS unplugged, I should be able to confirm grounds, correct?



Just a little confused on what I should be checking next...



I feel so cheated, I try to treat the truck so good but no love! I shudder when I think of the dealer working on my truck. I want to have this problem diagnosed before I take it in.

 

[Marco]

If the ground is lost, can the computer still read the apps voltage or is that the problem? With my multimeter I grounded the common side to chassis which would explain why I could see the . 44v reading. Maybe the computer couldn't... could this be the cause of 0122 engine code? Without a ground there was no signal so the computer reported a low voltage?

Yepper. Try to check the APPS ground wire with a ohm meter on pin 11 of the ECM plug. If you have problems with that wire cut it and provide a ground from the negative pole of the batterie. Don't ask how I know... .



Marco

 

[CJ Lagos]

Is pin 11 on the ECM just for the APPS or is this a common ground for all the sensors? I guess I'm confused if ground on ECM pin 11 is going in and out, why am I only seeing a problem with APPS. How can the other sensors be functioning?



You suggest to provide ground off the battery instead of letting the ECM provide ground to the wire coming into pin 11... that makes sense. Would it be a bad idea to add a piggyback ground and still leave 11 plugged into the ECM?

 

[Marco]

Several grounds are joint into pin 11. Let's say for a moment the ground wire for the APPS is broken off that joint. Voilà...

That's why I say to simply cut the ground wire close to the APPS and provide it with ground from the batterie. That's IF you find the APPS ground to be bad.



Marco

P. S. Piggyback? Why not?

 

[CJ Lagos]

Thanks. I checked the grounds when cold and they both were fine. The truck got worse so I took it into the dealer. Only 2000 miles before my 7yr/70k miles warranty is up. I figured I'd better take advantage while I can.



I hope they don't blame the banks brake, it taps directly into the APPS.

 

[CJ Lagos]

Turns out the APPS or any electrical stuff is only covered under the 3/36 warranty.



They think the problem is the rear speed sensor so I will replace that and see what happens. This would explain why I always saw a correct voltage reading from APPS.



My speedometer has always worked but I have 4 wheel abs.

 

[Marco]

What has the rear speed sensor with the high idle to do?



Marco

 

[CJ Lagos]

They told me the speed sensor can cause high idle as well. As luck would have it, when I pulled up to the service bay the truck was idlling at 1000rpm so I was able to show the service manager what the problem was. Now that I know APPS/electronics aren't covered under warranty, I'll never go back. I do however have a strong suspicion they are "throwing parts" at the problem. The speed sensor is only $35 so it is worth it to me just to be sure. Perhaps if the part wasn't such a high failure item I wouldn't be so inclined. The only thing that bothers me is the 0122 code I saw for low APPS voltage.



A friend of mine had a similar problem when his speed sensor went out.



He thinks the computer will use the speed sensor to keep the motor from stalling out. So, if you're on a full throttle acceleration and abrubtly take your foot off the gas, it steps the idle down gradually instead of cutting all the fuel. I think this can keep the motor from stalling? I guess this is similar logic to the IAC motor on modern throttle bodies.



This makes sense because I've noticed that at stop lights the idle will drop a little bit once you come to a complete stop.



My problem is pretty bad and fairly reproducable. I should get a good idea if the problem is fixed or not. Knock on wood...

 

[CJ Lagos]

Well I changed the speed sensor but it didn't help. Then I connected the apps ground wire at the plug directly to ground. It seemed to be better but still isn't right. I guess next step is a new one?

 

[2-ND TIME]

Marco can I ask for some info please?

Marco can you give me to voltage spec's for pin #5 the fuel shut off please. And or anything else if so please. If you like PM me. I have 1 volt peek to peek. and it looks terrable. The sheet is in my readers rigs it is tooooooo complicated for cryslurrrr and the other.



Thanks 99 JUNK.

 

[Marco]

Your readers rigs? = No pics show up for me...





Marco

 

[CJ Lagos]

Ordered the new APPS (53031576AD), $365. Hopefully this will fix it for good, tired of thinking about this.

 

[CJ Lagos]

I can't believe how easy these are to get off the truck. Mine is a manual with electric cruise so only one cable to pop off. I'm replacing the vacuum pump seal and it is nice to have the room with apps and intake off.

 

[CJ Lagos]

Happy to report the new APPS fixed my problems. Oo.

 

[HBarlow]

I've replaced two APPS modules this year. Both times the first indication of a pending problem was the engine would fail to return to normal idle speed. Normal idle speed is 875 rpm. Before the APPS failed I experienced intermittent idle speeds of 950 - 1000 rpm.



Harvey