Where do the pedal wires go? Gen IV

[bigmoe]

2008 5.3 from a Tahoe. I got the original ECM/TCM and wiring harness with the motor. I also got the pedal with about four feet of wiring attached. There's a brake light plug part way up and then bare wire ends where it was just cut off. Where do these pedal wires go? Does a Gen IV have a TAC module or does the ECM have wires that go to the pedal?

[ls1nova71]

No TAC in a GenIV, the wires go straight to the ECM.

[bigmoe]

That’s good news. Any idea what the pinouts are called? I see on J1 pin 9 says brake lite switch. And on J2 plug I see pin 5 tac motor control -1- throttle body.

[kipps]

What ECM? If it's the E38, the pinouts are available on lt1swaps.com. There are probably others available there, as well.

[bigmoe]

Yes E38. I’m looking at the pin outs on LT1swaps.

[kipps]

A one year Alldata subscription is a very good investment for this. Mine cost somewhere around $30 dollars for the first vehicle, IIRC.

This diagram is from Alldata for a 2010 tahoe. The red text is my own addition, and shows the pin location for each of the wires on the ECM. I double checked it for accuracy.

[bigmoe]

Kipps, thanks! It says brake/clutch harness though. I’m away from home for the weekend but when I get home I’ll check the wire colours at the cut end of my partial harness. It would make sense that pedal would be in the same harness. There’s no clutch plug on my partial harness.

[kipps]

If I remember right, this is a small sub-harness that plugs into the main Instrument Panel harness. I "think" this harness served the accelerator and brake pedal, but I have no idea why they include "clutch" in that. I thought they did away with all manuals by this point.

Regardless, the connector shown should be identical to the one that plugs into your accelerator pedal. Check the wire colors to confirm.

All six wires can be run directly to the ECM. In the factory application, they went through the engine-to-IP connector and the IP-to-brake/clutch connector before they reached the pedal.

[LeesTruk]

I'll 2nd the Aldata purchase! When I installed the genIII 5.3l ('05 Tahoe) in my c10, the one yr. subscription proved very valuable, if only for the wiring diagrams

[bigmoe]

Kipps, good news. I just checked my sliced off piece of pedal/brake wiring harness. My pedal plug looks just like your pic in post 6 and all 6 wire colors correspond. (YAY!) It should be as easy as running them to the corresponding pins on the X1 connector.

The brake switch plug has 4 wires:

l.blu w/ white …. corresponds with pinout printout- X1 connector, pin 9
org w/ wh
pink
purple
I assume the last 3 are for the brake lights circuit.

There are 10 wires in total at the sliced end of the harness and two wires are purple.

[rodstored-72]

Originally Posted by kipps

If I remember right, this is a small sub-harness that plugs into the main Instrument Panel harness. I "think" this harness served the accelerator and brake pedal, but I have no idea why they include "clutch" in that. I thought they did away with all manuals by this point.

Regardless, the connector shown should be identical to the one that plugs into your accelerator pedal. Check the wire colors to confirm.

All six wires can be run directly to the ECM. In the factory application, they went through the engine-to-IP connector and the IP-to-brake/clutch connector before they reached the pedal.

so.. I have a 2013 4.8 Stock harness & ECM. I have ID. each pedal wires (6) from the ECM and the truck pedal with the (6) wire pigtail plugin. My question about the above is that the factory diagram shows "twisted pr" wires between these 2 connection points.I am under the impression this is important? also how specifically do you make the connection between the ECM wires to the pedal wires?

thank you for the time.....

[bigmoe]

Rodstored, Do you have the plug or some of that end of the wire? I think you need the diagram like the one Kipps posted except for your year. Then it's as simple as extending the wires from the ecm. I think it's rare that you get that end of the factory harness fully intact that goes down to the pedal because it's really hard to get out the way it snakes through the firewall so they usually cut it off. If you can get some of the far end at the pedal from your donor or from a same model at a wrecker you should be able to figure it out, extend the wires and piece it together.

[rodstored-72]

bigmoe, thank you for the reply. I have the pedal pigtail (about 6-8" long) and the wires from the ECM (per pin nos.) I also have the diagram that shows each end. in the diagram it shows a "direct" wire connection, but each wire(s) are indicated as being split into (twisted pairs-same AWG) and then back to at each connection end. I think? that there is a connector to do the "wire split", but not sure?
thoughts?

[AussieinNC]

Twisted pairs are made up of two insulated copper wires that are twisted together.

The twisting is done to help cancel exterior electromagnetic interference.

Crosstalk interference can come from other pairs within a cable or from other outside sources.

Last thing you want in a throttle control circuit is additional signals....YIKES...

The twisted pair of wires use the same single connector...

[kipps]

I'm a bit puzzled why the pedal wires would be in twisted pairs.

Twisted wires are usually carrying a AC voltage signal(e.g., speed sensor), or a binary data signal(e.g., GMLAN between computer modules).

The pedal is merely two voltage divider circuits. Each circuit has a 5v positive, a low-reference ground, and a signal wire. The signal wire is progressively moved from 5v to 0v, depending on its position. This is happening independently for both circuits that run through the pedal switch. I don't see how interference will be affecting these wires, since they're neither AC voltage or data.

[rodstored-72]

I am not a electrical guy.. as by my silly questions . I do have the Diagram that shows the connection from the ECM to the pedal.... it does indicate the wires are twisted pair. I have been told that if it indicates that then I need to make sure that I duplicate it, I figure that GM did it for a reason... a reason way beyond my expertise...

I am going to see if I can find a donor truck that might still have the connections. my main quarry is if the wires and purpose are the same from around the same years.... say a 2010 truck to a 2013 truck

[kipps]

Originally Posted by rodstored-72

my main quarry is if the wires and purpose are the same from around the same years.... say a 2010 truck to a 2013 truck

I'm not an much of an electrical guru myself. I know enough to get by. But like you, if I can't figure out why GM did something on the donor, I figure it was for good reason, and I try to duplicate it in my build.

I looked up the accelerator pedal position sensor(simply the complete gas pedal) for a 2010 and a 2013 Silverado 1500 on RockAuto. The pedal is listed under "interior." They carry identical part numbers for both years. In both 2010 and 2013, GM used the e38 ECM for these trucks. From this rudimentary research, I'd say it's safe to assume the pedal pinout I listed earlier will work fine for a 2013.

If you want to be more certain about a specific wiring question, but don't want to bother to buy the $30 Alldata subscription, find a friend who runs an independent mechanic shop. He'll have a yearly subscription to Alldata or something similar, and you can look up wiring diagrams for any vehicle on that.