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APPS Replacement APPS Replacement
MD-LUCKY
06-20-2010
Here is a quick article on how to replace your APPS on your 98.5 to 2004 pickup. The APPS is a sensor that tells the pump how far you are pressing the fuel pedal to the floor, and how much fuel the pump should add.


Basic tools needed:
13mm wrench
10mm bolt
Size 20 torx
Phillips and Regular screwdriver
Multimeter


The APPS is like many other electronic devices: it doesn't always completely "fail" and stop working. It can cause erratic issues, such as dead pedals, surging, and low feedback.

The symptoms I noticed was an occasional dead pedal at a specific point in the pedal. It didn't matter what RPM, what gear, or what speed: it was always the same point as I depressed on the pedal. This lead me to believe it was a failing APPS.

There is already a great article in the tech section on how to reset the APPS. There is another option for a very basic APPS reset, and if you notice any difference it is probably time to order a new APPS. Here are the steps for the most basic APPS reset:

Disconnect the batteries for +/- 30 minutes
Reconnect the batteries
Turn key to the on position
Slow depress the fuel pedal to the floor, and slowly allow it to come back to the idle position
Turn key off

If you notice any difference in how the truck drives after this basic reset, there is a good chance that it is time to replace the APPS.

I ordered mine directly from Timbo here: Contact Us . When I ordered there were no site sponsors that offered a replacement APPS. If that changes in the near future, I'd support the people that support us on this site.

The kit comes with everything you need, down to a paperclip that you can use to adjust the voltage. Here is what you get:

Click the image to open in full size.

Disconnect the battery cables before you start.

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Next, remove the black cover over the APPS:
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There are 2 plastic screws that hold the cover in place. One is easily visible at the top of the cover, the other is at the front of the cover under the radiator hose. You can see the second screw here:

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The screws are the standard Phillips screw, but they hold a small plastic tab through the cover and into the metal APPS holder. This picture should give you an idea of how the plastic tabs come out, and how to remove them and the cover:

Click the image to open in full size.

There is also a small catch at the front of the cover that you must press in while pulling the plastic cover off. Once it is out of the way, you can get to the 10mm bolts that hold the APPS in place.

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Remove these bolts, but do not remove the cables!

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Now you can get to the actual APPS. It is held in place using 2 size 20 Torx screws:
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Remove these 2 screws and you can remove the factory APPS:
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Disconnect the electrical connector from the factory APPS, and carefully install the new Williams APPS:
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The kit comes with new screws that use a standard Phillips head bolt instead of the torx head. Instead, I decided to reuse the factory torx bolts. As you install the sensor, be careful to gently twist the sensor until it fits flush against the bracket. Start the bolts but don't tighten them down entirely. Before you tighten the bolts down for the last time, you need to twist the senor clockwise and then tighten the bolts down.

Now it is time to adjust everything that you've installed. I was able to prop the senor up on the air horn using the factory wire loom against one of the boot bolts.

Click the image to open in full size.

The paperclip goes into the number 3 wire. Gently press the paperclip pass wire until it makes contact with the connector.
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Reconnect the batteries, and turn the key to the on position. Use a multimeter to check the voltage of the new APPS. The instructions come with an acceptable range, and mine fell almost exactly in the center of that range.

Click the image to open in full size.

Click the image to open in full size.

Adjust the idle screw using a size 20 torx.
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You tighten the bolt until the voltage just begins to rise. Mine took several turns before the voltage on the multimeter changed.
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Take your time with this step. I went back and forth on the adjustments several times, until I found the exact point that the voltage started to change. Once you find the exact point, twist back 1/2 turn. Your voltage is now set. Turn the key off.

Carefully route the wires back under the APPS and bolt everything back in place:
Click the image to open in full size.

Turn the key back to the on position, and slowly depress the pedal to the floor and slowly allow it to return to the idle position. Turn key off. Turn key back on and slowly depress and allow pedal to return again. Turn key off.

Start the truck and make sure that the idle isn't elevated. Gently press on the pedal and note how much travel is needed before the RPMs start to change. It should take minimal movement. If you are happy with the pedal travel, button everything up under the hood and you are finished! If not, repeat the adjustments on the voltage until you find a point that you are happy with the amount of pedal travel needed to increase RPM.

Finish up under the hood, and you are finished!

Click the image to open in full size.

Click the image to open in full size.  
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  #1  
outlaw99 on 06-20-2010, 05:33 PM
would the apps cause the truck to get horrible fuel mialege along with the dead pedal, or have any issues with a aftermarket box like robbing hp?
  #2  
MD-LUCKY on 06-20-2010, 05:43 PM
Quote:
Originally Posted by outlaw99 View Post
would the apps cause the truck to get horrible fuel mialege along with the dead pedal, or have any issues with a aftermarket box like robbing hp?
Dead pedal? Without question.

Bad fuel mileage? Probably not.

Robbing HP? Well, if it isn't reading correctly, it may not tell the pump that you are pressing the pedal to the floor.. So it may never give full 100% throttle.

Unfortunately it sounds like you are describing symptoms of a failing VP pump more than a failing APPS. Those are all common symptoms of a VP going out, and only 1 is common for a failing APPS.

If you have a known, good VP then you might consider a new APPS. However, those symptoms are more likely an issue with the VP pump. Surging, dead pedal, and sluggish feedback are more common symptoms of a failing APPS. Try the basic reset and see if those symptoms go away.. It's extremely easy (and free), and is a good way to diagnose issues.
  #3  
outlaw99 on 06-21-2010, 07:21 AM
Its a 04 cr...lol Just wondering trucks seems like it doesnt have much hp for whats done to it. thanks for the replys though, it throws a apps code and I get dead pedal, just wondered if it would kill the trucks fuel mielage or power, thanks again
  #4  
MD-LUCKY on 06-29-2010, 12:03 PM
Alright, I'm changing my opinion on the bad fuel mileage.

I'm putting a little over 160 miles per day on the truck right now, so I've had a chance to watch the fuel mileage.

Before the new APPS I was getting 18mpg combined like clockwork. Didn't seem to matter how I drove the truck; that was my mileage.

Right after replacing the APPS I noticed the mileage go way up. I hand calculate my mileage at every fill, and I don’t have one of those overhead read-outs. I went from averaging around 18 to 21.6 hand calculated on the next tank. I figured it was a fluke.

Tank after I got 22.8.

I'm just under half a tank left this go around and I've got about 400 miles on this tank, so it should be right up there again.

I've never got mileage like this before. Before the new APPS, I could count the number of times I broke 20mpg on 1 hand. Maybe it is just a fluke, but I guess it is worth mentioning. It is possible that the APPS has more to do with fuel mileage than I originally gave it credit for!
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