This weekend, I noticed the trip odometer was at 0 miles when I was filling with gas and I had not reset it. It appeared to work after I drove further. When I checked the odometer, it showed approximately 34,000 less miles than on my 2001 Tahoe. Even though the trip odometer appears to work, I is tallying about 20% less miles than actual. I have not had time to check in with a measured distance yet.

Any ideas here on what is wrong and what the solution might be?