Rick's Free Auto Repair Advice

Fuel Gauge not accurate on GM Vehicles

Fuel Gauge wrong on GM Vehicles

Owners of GM vehicles are reported problems with their fuel gauges reading low when the tank is full, or giving erratic readings. Start your diagnosis by checking the electrical connector to the fuel tank sending unit. The electrical harness should be visible near the right (passenger side) rear floor. Check the harness for an
y nick or scuffing and follow it to the electrical connector. Unlatch the connector and inspect for corrosion. If you find any, use electrical contact cleaner to clean it and apply a light coating of dielectric grease before re-connecting.

Next, check the resistance of the two wires going to the fuel level sending unit. The reading should be 40 ohms when the tank is empty and 250 ohms when the tank is full. If the connections are good and the ohm readings are off, that would indicate a bad fuel level sending unit. That’s located inside the tank and involves dropping the tank for replacement. HOWEVER, GM has just issued a TSB on this problem that applies to ALL GM vehicles and blames the high incidence of sending unit failures on high levels of sulfur in gasoline. The sulfur corrodes the sliding resistor mechanism and produces erratic and inaccurate gauge readings. To address this problem, GM has released a FUEL TANK ADDITIVE.

According to GM TSB #06-00-89-07BB, you should purchase a bottle of GM Fuel System Treatment Plus (part #88861011 for GM brand, 88861013 for AC Delco brand, and 88861012 in Canada) and add it to your tank at every oil change. The additive cleans the sulfur corrosion from the sending unit and prevents new corrosion by laying down a protective film. The additive also removes engine deposits.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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