// Install guides
ROTARY SWITCH — 01-04 DURAMAX 6.6L LB7
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 2001–2004 Chevy/GMC 2500/3500 6.6L LB7 Duramax. The ECM sits under the TCM in the fender well, so the TCM comes out first to reach the blue ECM plug. Two pins go into the blue connector, then the switch runs through to the cab. Signal, the purple wire: blue connector pin 69. Ground, the black wire: blue connector pin 49. Kit contents: A. Loomed electrical wires B. Dial stickers C. Switch control board D. Switch knob E. Allen wrench
Steps
1 Remove the TCM cover
The black plastic cover sits over the TCM in the driver side fender well. Undo the two fasteners circled at its top corners and lift it off.
2 Lift out the TCM
With the cover off, the TCM lifts up out of its bracket. Bring it up far enough to reach its connectors.
3 Disconnect the TCM
Unplug the TCM connectors and set the module aside so you can get at the ECM beneath it.
4 Remove the ECM cover
Pull back the rubber cover that shields the ECM connectors.
5 Unbolt the blue plug
The blue ECM connector is held on by a centre bolt, circled in the photo. Undo it and draw the plug off the ECM.
6 Remove the blue cover
Lever the blue cover off the back of the connector to get at the wires.
7 Pins now exposed
With the cover off you can see the pin block from the wire side. Pin numbers are moulded into the connector body beside the rows; count along to find 69 and 49.
8 Insert the new pins and wires
Signal, the purple wire, goes into pin 69 of the blue connector. Ground, the black wire, goes into pin 49. Push each until it latches and give a light tug to confirm it is seated.
9 Reassemble
Refit the blue cover, bolt the plug back onto the ECM and refit the ECM cover. Reconnect the TCM, drop it back into its bracket and refit its cover. Route the switch wires into the cab, mount the switch and reconnect both batteries.
10 Check the switch pin position
The pin on the switch control board should sit between the 5th and 6th slot, as pictured.
11 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.