// Install guides
ROTARY SWITCH — 04.5-05 DURAMAX 6.6L LLY
Unplug both batteries before installation. Never work on a hot vehicle. Let it cool before starting, and wear eye protection when working on or under it. By installing this product you assume all risk and liability for its use.
Wiring the rotary shift-on-the-fly switch into the ECM on a 2004.5–2005 Chevy/GMC 2500/3500 6.6L LLY Duramax. Two pins go into the grey C3 connector on the ECM, then the switch runs through to the cab. Signal, the purple wire: grey connector pin 32. Ground, the black wire: grey connector pin 50. Kit contents: A. Loomed electrical wires B. Dial stickers C. Switch control board D. Switch knob E. Allen wrench
Steps
1 Find the C3 grey connector on the ECM
The ECM has three connectors stacked on its side: C1 at the top, C2 in the middle and C3 at the bottom. The bottom grey one, C3, is the one you wire into.
2 Lift the grey lever and detach all three plugs
Push the release button in to free the grey lever, then slide the lever towards the front of the truck as far as it will go. That levers the plug off the ECM. Do the same on all three so the bottom one can be worked on freely.
3 Take the bottom grey connector to the bench
This is the one you will open up. The next steps are easier with the plug out of the engine bay.
4 Remove the pin lock
The pin lock is the coloured retainer on the face of the connector. Ease it out with a small flat screwdriver and keep it; it goes back in at step 11.
5 Release the black cover
Push a flathead screwdriver into the unlock clips on the side of the black cover to free them.
6 Remove the black cover
With the clips released, lift the cover off the back of the connector to expose the wires.
7 Top view of the connector
With the cover off you can see the wires entering the back of the pin block. This is the side you insert the new pins from.
8 Locate the correct pin positions
Pin numbers are moulded into the back of the connector body at the ends of each row. Count along from them to find pins 32 and 50.
9 Remove the pin fillers
Pins 32 and 50 are blanked with fillers from the factory. Push each filler out from the face of the connector so the new pins can go in from the wire side.
10 Confirm pin 32 from the wire side
Before inserting anything, find pin 32 from the back of the connector and check it lines up with the position you opened on the face.
11 Insert the pins and refit the pin lock
Signal, the purple wire, goes into pin 32. Ground, the black wire, goes into pin 50. Push each until it latches, then reinstall the pin lock so the pins cannot back out.
12 Reassemble the connectors
Refit the black cover, plug all three connectors back onto the ECM and lock each grey lever. Route the switch wires into the cab, mount the switch and reconnect both batteries.
13 Check the switch pin position
The pin on the switch control board should sit between the 5th and 6th slot, as pictured.
14 Troubleshooting
You need a voltmeter. Set the switch to position 1 and turn the key to Run, engine off or on. Test the switch-on-the-fly wire, the purple one. The reading varies a little within each level (4.0–4.9 in position 1, for example) but should be close to:
Level 1: 4.5 V
Level 2: 3.5 V
Level 3: 2.5 V
Level 4: 1.5 V
Level 5: 0.5 V
High idle: 5.0 V
If the readings do not match, check the connections and pins for anything bent or broken, and make sure no debris is stopping a pin seating fully. If it persists, get in touch with us.