Gas needle swings back, forth, settles on halfway

Dear Doctor: I have a 2000 Chevy Blazer with a gas gauge that acts as if I’m driving through a magnetic field. When I shift the transmission into park or neutral the gas gauge needle goes back and forth from E to F continuously. When I put the shifter into drive it will register a tank of gas from full to halfway only. After that, it stays at the halfway mark. I must use my trip meter so that I do not run out of gas. Someone told me it is an electronic problem and will cost around $1,000 to fix. What does the transmission shifter have to do with the fuel-sensing gauge? Jim


Dear Jim: The first step is to connect a professional scan tool to the vehicle and look at the actual information the fuel sender unit is sending to the computer. A very common problem is the dash cluster. We take them out and send them to be repaired on a weekly basis. The cost is in the $350 range for the majority of dash clusters — regardless of the make of vehicle. If the problem is the fuel sender unit, then the cost should be around $600 on average for a replacement module.

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