There's a locker position sensor in the axle housing and if the gearing shop doesn't know how to properly install the carrier to properly engage that sensor problems will develop. One is that the locker will be forced into a partially engaged position even when the locker is not locked, even when you're in 2wd. Two the sensor will indicate the locker is locked all the time, when it is not, which will cause the locker lights to flash, warning of a problem.
Here are a few pics I made during my regear and one illustration I found when I had a similar problem after my first axle regearing was completed. We were stymied for a day or two until research pointed at the locker actuator sensor.
The locker sensor sensor is at the top here shown in its correct position. When the locker actuator engages it pulls the sensor tip toward the left indicating the locker is engaged. Its mushroom shaped tip must be positioned on the 'other' side of the actuator plate so this can happen.
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This shows the sensor in the top center of the photo. That funny red thing stuck in it is a short piece of wooden toothpick. Its temporary job is to hold the sensor out fully until it can be released after the carrier has been installed. Attached to it is a short length of fishing line so the toothpick can be removed once the carrier is properly positioned.
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This shows the actuator plate at the very top of the carrier. There's an air bladder inside it that when inflated pushes against the locker to lock it. The sensor detects the position of this actuator plate. The "ears" that normally stick up at a 90 degree photo have been temporarily bent down during the bearing removal process.
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