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Discussion Starter · #1 · (Edited)
Well, the truck started throwing a P2121/2122 code among some pretty wet weather recently. For about a week, even if I cleared it, it would come back pretty shortly after. I wasn't noticing any symptoms such as dead pedal during this time, except once when I was running my EB. Normally when you hit the pedal, the EB cuts out, this time it didn't. Other than that there were no symptoms.

That being said, I jumped on the research train. Found that this was an APPS related issue. In my research, I found that the APPS units (since mine is an 04.5 6sp, my APPS is under the driver side battery tray) are very expensive, even if you can find them anymore. Most of the time too, just switching the APPS unit doesn't solve the problem. The APPS signals go through a few connectors before it even reaches the ECM, so to track any wiring issues can be a big problem. So there's a couple ways you can go about solving the problem. Both include wiring the APPS directly to the ECM so it doesn't go through all of the harnesses.

You can keep the original APPS and just cut the wires on the connector then wire them directly to the ECM, or you can "upgrade" to the 05+ APPS unit that is on the accelerator pedal, which seems to have little to no issues. So that's what I elected to do.

This thread was a HUGE help in this process, but I figured I'd do a complete write up on it for anyone that wants to do this conversion:


That being said, if you have an 03-04 truck, any of the 05+ APPS units on the pedal work. But, I believe (and someone can correct me if I'm wrong) after 06 (so 07+) you can't just replace the accelerator pedal, you have to replace the entire pedal housing (that mounts the brake, clutch, and acc. pedal).

So, if you want to do this the easy way for us 03-04 people, you want to source the accelerator pedal/mounting bracket from a 2005 or 2006 truck. Gas or diesel, it doesn't matter. It is a direct bolt up.

Here's the pedal I had pulled from car-part.com (2006 truck). I think it cost me about $35 for everything. Make sure you ask the company for the mounting bracket. Most of them I saw didn't picture or say the bracket was included, so I had to ask for it. You don't need the hardware if they don't provide it. If you can, also make sure to ask for the connector and some extra length of wire:

Bicycle handlebar Bicycle part Wood Automotive tire Cable


Next up is to understand the pinout of the APPS connector at the pedal. @cumminsturbofreak was a huge help along the way as well as @StealthDiesel. This website you can look up the year of your truck and then search "accelerator" and it will show the connector and pinout.

You will also need your FSM so that you know the pinout of the APPS at the ECM. You are going to eventually have to cut the wires (if you choose to add a connector like myself). In the 04 FSM, to save you from having to search forever, the APPS wiring diagram is on 8-30-65. It's actually on 2 pages as there are 2 wires in one connector and 4 wires in the other.

I chose to use a wiring bundle. 6 strand, 18 ga. I purchased this on Amazon (click link for product). I've used this for other projects and it's a very clean way to do thing. As well, it fits perfectly through the grommet in the firewall (get to that later).

First step is to wire your pedal connector. Here's a few of the things you'll need:

Bicycle handlebar Font Cable Gas Wire


To make the connections, you can solder, heat shrink with quality, non-insulated butt connector, or even re-pin the connector. If you choose to crimp, make sure you use a quality crimper and the appropriate sized connector. If you want to find the pins, I de-pinned a terminal for visual, but I could never find what part number it was, but it looks like this:

Hand Musical instrument Wood Guitar Audio equipment
Light Product Black Camera accessory Material property


Make you connections then take a picture of what color on the connector goes to which color in your bundle. You don't want to forget this:

Electrical wiring Cable Electronic device Wood Electrical supply


Tesa tape is your friend. I also put the sheath back on the section of bundle just in case it rubbed on anything:

Wood Hardwood Cable Wire Electric blue


Here's the final product. You want to make sure you have enough bundle length. I made sure I had enough excess that if for some reason I have APPS issues due to my connections, I can pull enough bundle back through the firewall and pin it directly to the connector:

Pliers Wood Cable Auto part Gas


Now that's complete, it's time to go out to the truck. Remove the wheel and fender liner, you're going to want as much room as possible to work. Then you can go un-bolt your accelerator pedal. It's a royal PITA. The design is so bad. Getting the nut off the stud is easy (you'll see it on the firewall), but there's a hidden bolt (shown arrow below) that's around the backside of the bracket and you can't see it. It took a long extension and a u-joint to get to it:

Tire Wheel Vehicle Hood Automotive lighting


Once that's out of the truck, you can pull the grommet/cable out of the firewall. I just yanked on the APPS cable sheath and it popped the grommet out. You need to work the grommet off of the plastic housing that captures the end of the cable:

Hand Automotive tire Fishing rod Gas Tool



Automotive tire Bicycle part Rim Gas Nickel
 

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Discussion Starter · #2 · (Edited)
Here is a bench test of the grommet with the wire bundle. FWIW, the grommet hole is about 3/8" in diameter:

Wood Audio equipment Gas Cable Wire


Here's an image of where you need to replace the grommet back to. I suggest using some sort of grease to get the grommet to push back in place. I fought replacing it in its hole until I did this:

Automotive tire Hood Motor vehicle Synthetic rubber Tread


Now that it's back in, you can run your wire bundle through the firewall out to where you'll be working. Also at this point, you can go ahead and install the new pedal.

In the image below, the yellow circle is the stud the pedal bracket mounts to, and the blue circle is where the lag bolt screws into (it's not blind when you install the new pedal). You can see my wiring bundle running through the grommet as well:

Automotive tire Bicycle tire Rim Bicycle part Fender


Here's the new pedal mounted up:

Motor vehicle Automotive tire Automotive exterior Electrical wiring Automotive fuel system


Automotive tire Motor vehicle Vehicle Auto part Automotive wheel system


Now that's completed, time to work in a really confined area.

If you want, you can just leave your old APPS unit under the battery, but since it was only 3 screws to remove it, I decided to yank it out. If you leave it, just ziptie the cable somewhere out of the way. If you want to remove it, disconnect the connector by hooking a 90* pick on the backside and pull that red tab towards the back of the truck. you will not be able to see the red tab when you are doing this since it's towards the engine. Photo just to show what you're trying to release:

Hand Finger Gesture Thumb Wrist


Old APPS unit and cable out of the truck:

Flooring Asphalt Military robot Geology Automotive tire


I just zip-tied a sandwich bag on the end of the APPS connector since it won't be doing anything:

Motor vehicle Automotive tire Automotive fuel system Car Automotive design
 

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Discussion Starter · #3 · (Edited)
Next, I suggest routing your wire bundle. I chose to route it behind the hard fuel lines, then up against the block with the engine harness. I added some corrugated sheath just to that area to prevent any rubbing issues:

Automotive tire Gas Auto part Composite material Metal


However you route your bundle, you want it to terminate down by your ECM. Just remember to always leave a bit extra.

Before you move forward, I highly suggest that you make yourself a diagram, however suits you best, to know what wires/pins you are after on the ECM. It gets messy in there. Honestly, the hardest part of this whole project was removing the 17 year old tape on the wires. Here is the diagram I made. I cut and pasted images of the C1 and C2 connectors for the ECM, as well as the pin #'s from the FSM, then I made a key for what colors I was after and what color in my bundle needed to be attached to which wires. Here it is, if you open it in a new window, it will be full sized:

Rectangle Black Slope Triangle Font


It looks confusing but it's not bad. Oh and the connector shown, that was from the website I linked up in the first post.

Once that's established and you know what you're after, there's a couple ways to go about this next part. You could purchase some ECM pins and de-pin the wires from the old APPS unit and let them just hang, then re-pin your wires into there, or you can do as I did, which was cut the wires up high then pin those into a Deutsch connector.

Before you do ANYTHING with your ECM, disconnect the negative battery terminals on both sides of the truck. Then you can remove your ECM plugs C1 and C2 (an allen bolt holds them in place):

Tire Automotive tire Automotive lighting Wheel Motor vehicle


Find your wires, one connector at a time, and cut them to the appropriate length. Check and double check the diagram you made above with the colors. Colors for different years will vary. My truck is an 04.5 manual, so if you have the same truck, you're in luck and can just follow my diagram. If it's not, the concept is still the same but consult your FSM for wiring colors:

Finger Electrical wiring Cable Gas Auto part


Here's the connector all wired up:

Hood Motor vehicle Automotive exterior Electrical wiring Automotive fuel system



You can now move on to making your connector on your wiring bundle. Here's an example of the Deutsch connector pins. You need a special crimp for the closed barrel type pins as shown. Make sure to follow your diagram so the plugs are mating the correct wires!:

Hood Gadget Automotive exterior Grille Bumper


Sorry about the flash on the crimpers:

Automotive lighting Bicycle handlebar Sports equipment Glove Sports gear


Completed connector on the wiring bundle:

Automotive lighting Automotive tire Motor vehicle Hood Automotive mirror


You can plug everything back in, finish up your wire routing if you need to, and walla! You can see my "extra" loop of wire kind of at the end. Just in case. There's enough extra to pull to the ECM if I ever need to pin it directly, and enough to pull into the cab if I ever need to directly pin to the pedal connector. Oh, and I re-wrapped the ECM wires with Tesa Tape. That stuff is amazing.

Tire Automotive tire Wheel Motor vehicle Tread


So why did I choose to use a connector? Well, if something ever happens with this and I need to revert back to the original while I'm fixing or troubleshooting this APPS system, all I need to do is make a harness that goes directly to this plug. Pretty simple and I don't need to mess with the ECM plugs again.

The pedal is much "lighter" and more responsive than the cable pull version that it replaced. It's going to take some getting used to but once I do, it's going to be a much bigger difference at the skinny pedal. The couple times I've driven it so far I've been very impressed. Hopefully don't have to mess with any more codes.

Enjoy your updated APPS!
 

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Awesome write up. Im in the process of starting this but am having an issue finding the exact colors of the wires to match up to what im searching. What year is your truck?? Very confused because whatever i bring up nothing matches to my setup. Someone said theres 2 versions of this in the manufacture year of 2003. Im wondering if the wires just changed but where each input is the same since the bellcrank is the same. I dont really want to dig into this without a good idea on what i have here lol. Very nice write up though. I hate how hard the throttle is and can be very touchy at times.
 

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Discussion Starter · #5 ·
Awesome write up. Im in the process of starting this but am having an issue finding the exact colors of the wires to match up to what im searching. What year is your truck?? Very confused because whatever i bring up nothing matches to my setup. Someone said theres 2 versions of this in the manufacture year of 2003. Im wondering if the wires just changed but where each input is the same since the bellcrank is the same. I dont really want to dig into this without a good idea on what i have here lol. Very nice write up though. I hate how hard the throttle is and can be very touchy at times.
Not sure I understand. You need to look at your FSM for your year and see what wire colors correspond to your APPS/TPS at your ECM. That's what matters because youre going to tie into those.
Then you need to go to that site I provided and you want to look up the 05 or 06 truck APPS wiring connector at the pedal. Whichever your donor pedal/APPS unit was from.

Then it's connect the dots between your ECM wires to your donor pedal.
 

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So if you go to that site you put in 2004 m/t? Thats the issue im having. I wanted to cut that connector off but for some reason the wires on the end where that plug are not corresponding with the colors on the connectors.cctools.com site. Do the colors change coming out of the ecm? I wanted to just test the setup before i did anything by plugging each wire end into the old harness. Someone told me that since my build date is 1/03 then its considered an 04. If i type in that plug number in the only thing that comes up is 04 and newer. Just confuse on this lol. How does your throttle feel now?
 

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Electronics on the 2003 MY sux, changes made at the 2003.5 (built 01/03 +) stage causes the wiring schematics to be off from the 2003 FSM, so maybe you need 2003 or 2004, not sure.
Not looking forward to this project if ever needed.
 

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So my truck was built on 1/24/03 . So would that be considered still 03 and not 03.5? This is confusing the hell out of me. I downloaded a fsm for both 03 and 04 and the connectors are the same along with the pin ends doing the exact same thing. 1 through 6 are the same except wire colors at the connector. I basically want to just test this to see if it works lol.
Electronics on the 2003 MY sux, changes made at the 2003.5 (built 01/03 +) stage causes the wiring schematics to be off from the 2003 FSM, so maybe you need 2003 or 2004, not sure.
Not looking forward to this project if ever needed.
 

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Discussion Starter · #9 ·
So if you go to that site you put in 2004 m/t? Thats the issue im having. I wanted to cut that connector off but for some reason the wires on the end where that plug are not corresponding with the colors on the connectors.cctools.com site. Do the colors change coming out of the ecm? I wanted to just test the setup before i did anything by plugging each wire end into the old harness. Someone told me that since my build date is 1/03 then its considered an 04. If i type in that plug number in the only thing that comes up is 04 and newer. Just confuse on this lol. How does your throttle feel now?
When I go to the connector site, I actually put in a 2006, because that's the MY that my donor pedal was from. I confirmed the wire connector colors and pinout of the plug at the APPS (ON in the pedal) matched that diagram. For the 2006 year, there are 2 color options for pin 1 and pin 6. If you don't have 1 color, you will have the other ( I suggest follow this thread and look up like you are using a 2006 pedal, just to understand).

If you wanted, you could also confirm your colors on your MY truck. You'd be interested in the colors at your plug to the unit (I'm guessing yours is under the intake horn?) From the site. If they don't match, don't worry. What you're really interested in is the pins on the new plug from your donor pedal (there's some K# as you can see in the diagram I made) match the K# wires in the FSM, then follow it to the ECM and the schematic will tell you the pin number.

Now you have:
2006->K# connector->pin# on connector.
2003/2004->K# ECM->pin# on ECM.

Combine those 2 it will give you:
2006->pin# connector->2003/2004->pin# ECM

To answer your question about the pedal feel, it's awesome. It's very light since you basically have zero resistance from the cable. It's a lot easier to feel how much there is one the old unit is off the truck.

@tryNto, it's not a bad job at all except the confined quarters you have to work in. Like I mentioned the worst part was actually removing the old loom off the wires. Messy!

This project settings intimidating at first but it's really not.

My biggest suggestion would just be to understand the connections first. Pretend you're MY is an 04.5 like mine and follow/understand the diagram I created. Lol at the colors of my 2006 connector and compare them to the diagram I created. Once you understand that, it will be easier to apply this to your own MY.
 

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So my truck was built on 1/24/03 . So would that be considered still 03 and not 03.5? This is confusing the hell out of me. I downloaded a fsm for both 03 and 04 and the connectors are the same along with the pin ends doing the exact same thing. 1 through 6 are the same except wire colors at the connector. I basically want to just test this to see if it works lol.
You, like I have a 2003.5 because of a build date in 2003.
Model Year starts in about July of the previous calendar year. So 2003 became available in July 2002.

This project seems intimidating at first but it's really not.
My main thought is the issues I have read about on the wiring changes between 2003 and 2003.5. With a lot of the 2003.5 wires not matching the 2003 FSM.
That's all. I know I can do it if it comes to that.
 

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I have a 2004.5 as well but it’s an auto. Or was, I just swapped to a G56. Instead of tracking down the under battery APPS I elected to swap the pedal after seeing your post here. As far as the ECM connections they’re obviously different. How exactly would the wiring correspond to yours so I can get it hooked up correctly?
Rectangle Font Parallel Screenshot Number
 

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I have a 2004.5 as well but it’s an auto. Or was, I just swapped to a G56. Instead of tracking down the under battery APPS I elected to swap the pedal after seeing your post here. As far as the ECM connections they’re obviously different. How exactly would the wiring correspond to yours so I can get it hooked up correctly? View attachment 945618
Wiring positions at ECM connector is different between manual and auto.

You need to extract the wiring and contacts for the Auto APPS from the ECM connector. Then you make your Manual APPS harness with contacts and insert into proper positions.

Take it slow. It’s a pain to remove contacts from the DRC connectors and it’s easy to get lost.
 
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Wiring positions at ECM connector is different between manual and auto.

You need to extract the wiring and contacts for the Auto APPS from the ECM connector. Then you make your Manual APPS harness with contacts and insert into proper positions.

Take it slow. It’s a pain to remove contacts from the DRC connectors and it’s easy to get lost.
How do I know which would go where though? That’s where I’m lost. I don’t understand electrical at all. So if you could really dumb it down for me? I have no idea how exactly my APPS wiring would correspond with a 2007 pedal (that’s what I found and it fits).
 

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Discussion Starter · #14 ·
How do I know which would go where though? That’s where I’m lost. I don’t understand electrical at all. So if you could really dumb it down for me? I have no idea how exactly my APPS wiring would correspond with a 2007 pedal (that’s what I found and it fits).
Have you read through this entire thread? First thing you need to do is FULLY understand what I did. Pretend you had a manual from the get go. Pretend you had my truck. Follow this thread and understand what I did. I laid it out in Layman's terms as best as I could. I really tried to simplify it with diagrams and such.

Then, and only then (after you understand this process on a normal manual truck), should you start trying to understand the auto swap side of things. But you're going to need fundamental understanding of what's going on first.
 
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Have you read through this entire thread? First thing you need to do is FULLY understand what I did. Pretend you had a manual from the get go. Pretend you had my truck. Follow this thread and understand what I did. I laid it out in Layman's terms as best as I could. I really tried to simplify it with diagrams and such.

Then, and only then (after you understand this process on a normal manual truck), should you start trying to understand the auto swap side of things. But you're going to need fundamental understanding of what's going on first.
I understand what’s going on and I’ve read the thread a few times through. I’m only asking questions because the pins on the auto are obviously labeled differently than the manual. So I’m trying to figure out what auto pin out would take the place of each manual pin out. That part I don’t understand.
 
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