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2006 Chevrolet Silverado Duramax Diesel: U0100 and P0700 Error Codes, Transmission Shifts Like Trailer Mode

Model: 2006 chevy Silverado Duramax diesel Fault Code: P0700 Posted: 2016-12-26 16:25

My 2006 Chevrolet Silverado Duramax diesel truck has developed a check engine light issue. The transmission shifts as if it's in trailer mode, and the onboard diagnostic system shows two error codes: U0100 and P0700. The vehicle is stock with no modifications, plug-ins, or performance tuning. I've tried clearing the codes using a standard handheld OBD2 scanner from an auto store, but the fix only lasts a few minutes. A professional mechanic cleared the codes using a high-end diagnostic tool, and the issue has resolved temporarily. I'm seeking advice on how to properly diagnose and resolve this issue, especially since U0100 indicates communication failure between modules (likely TCM and ALDL), while P0700 points to a TCM-related problem with no transmission-specific codes.

Related fault codes
P0700U0100
Comments (4)
Anonymous 2016-12-27 08:20

Have you made any recent modifications or installations? Check if the Transmission Control Module (TCM) is receiving power and communicating properly. Code U0100 typically indicates a communication issue between modules, while P0700 suggests a TCM fault—note that no transmission-specific codes are present. Ensure there are no aftermarket devices plugged into the ALDL or any chips/programmers installed.

Anonymous 2016-12-27 08:49

No modifications or after-market installations have been made. The truck is completely stock. The only difference in my routine was plugging in a block heater for one hour before starting the engine.

Anonymous 2017-01-10 16:34

I'm experiencing the same issue on my 2006 Duramax, though mine has been tuned. The problem only appears when I use the block heater—this suggests a possible temperature-related sensor or communication fault during cold starts.

Anonymous 2017-01-28 17:36

It's generally recommended to only use a block heater in temperatures below 0°F (or 0°C). I tried clearing the codes with a standard auto store scanner, but it only worked for a few minutes. After my mechanic used a professional-grade diagnostic tool to clear the codes, the issue disappeared temporarily—this indicates a potential communication or sensor issue that requires deeper diagnostics.