OK so I have an 02 Silverado 2500 HD four-wheel-drive and couple months ago it was broken into. They cut the 3 wires on the top of the ignition but luckily they were unsuccessful at stealing my truck. Anyways so I’ve been having the theft deterrent problems since. I have replaced the starter, the ignition switch and the wiring harness, the ignition housing, and the ignition lock cylinder. I have also performed a number of factory reset sequences as well as a security reset with an OBD reader but nothing works. My truck will not shift out of first and my speedometer isn’t working. I’ve also changed the speed sensors in the transmission and the connectors for the speed sensors. I’ve also ran through all the wiring with a multimeter and everything seems fine. I am running out of ideas on what it will be so any help would be much appreciated.

 

Is the security light flashing?

The theft deterrent system on these trucks is designed to cut off fuel supply when attempted theft is detected, but it won’t put the truck in limp mode or mess with any of the gauges.

There’s multiple known issues with the clusters, wiring and BCM’s in these trucks - I’m sure the attempted theft was the catalyst for the issues you’re experiencing but it’s more likely a separate cause.

Are there any trouble codes and what are they?

 

The security light only blinks when the ignition is turned off and stops when the ignition is turned to the on position. And the codes that it’s throwing are: U1301
P1631
P1637
P1638
P1626

and I appreciate you taking the time to help me out with this.

 

The U1301 needs to be the focus of diagnosis - it can cause the other codes to set due to lack of communication between the PCM and other modules, such as the BCM which is also the theft deterrent module. The class 2 network is what all modules in the truck use to communicate and if it’s down it will cause limp mode and the flaky cluster operation.

U1301 specifically refers to high voltage on the data circuit, so this could be caused by a short to voltage or malfunctioning module.

First, key on engine off, check voltage at pin 2 (purple wire) of the Data Link Connector (DLC - aka the OBD plug). It should be approximately 7.0 volts.

How much voltage is present will determine the next steps, but most likely you’ll need to access the network splice pack and begin isolating the circuits. I’ll try to find a location graphic for you, but it’s located behind the left end of the dash, near the headlight and transfer case switches. It’s just a plug with several purple wires coming out of it.

MAKE SURE THE KEY IS OFF BEFORE REMOVING THE SPLICE PACK CAP!!

Once the cap is off, turn the key back on, and check voltage on each terminal one at a time. If you find one or more terminals with more than 7 volts, those are the circuits to focus on. Remove the terminals from the splice pack and isolate them to prevent accidental grounding. Once removed, reinstall the splice pack cap and check voltage at pin 2 of the DLC again - it should be 7.0 volts now.

Let me know what your results are and I’ll explain the next steps.

 

Sorry it’s taken so long to reply back. When you say the network splice pack are you referring to the splice pack 205?

 

Yes. It’s typically easier to see if you remove the trim panel below the steering wheel.

 

What about when you have less than 7.0V?
I have an 02 avalanche with u1301, 1626, p1860, and p0134. I only have .22-.56v on Pin2/ppl on the DLC connector

 

As long as the key was on when you checked it, That reading indicates a short to ground or high resistance on the data circuit.

Your steps for isolating the problem are practically the same as what I suggested for the O.P. With a slight variation.

Disconnect the negative battery cable and check for continuity to ground on the data circuit at the DLC.

Next, locate and unplug the splice pack under the dash and check each circuit for a short to ground. If you find one, that’s the circuit to focus on.