U2106

[Somis Duramax]

I finally got around to my gauge install. Got a copy of "Got Gauges" and started. Gauge pod was drilled in the wrong spot for the speaker and Autometer is working on the problem. Ran the boost line and tapped the light wiring to the INTPARK fuse in the engine compartment. None of the wiring is hooked up because the pod doesn't fit. Anyway after restarting the truck the SES light was on so I downloaded the faults:U2106 Throttle Actuator. Cleared fault,keeps coming back. Rechecked all wiring etc. no joy. Then also noticed that there is no underscore under the PRND21L indicator and it goes into gear with a horrific clunk. Removed The Juice, cleared code still no good. Any of you great wizards have any ideas? By the way truck is a 2003 C3500

[mdrag]

Somis,

Here is a link for OBDII codes:

www.obdii.com

General Motors U2106 Lost Communications with Transmission Control System

I would check the connectors to the NSBU (neutral start backup) switch to make sure they are secure. The NSBU switch is mounted on the driver's side of the Allison. If you click one of the links in my sig, there is an album with pics of the NSBU switch.

If the connectors are secure, you MAY have a bad NSBU. I replaced mine as a preventative measure since the BLACK old style NSBU switch has known issues, and the new TAN switch is an improved version. The part# for the new switch is clearly displayed in the pictures and was about $54 at my local Allison dealer.

I'm going to move this topic to the 2500HD/3500 HD Trucks & Drivetrain forum, since your problem MAY be more appropriate for that forum (drivetrain related). Good luck.