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Low fuel light comes on even when fuel is in tank. I had the…

Low fuel light comes on...
Low fuel light comes on even when fuel is in tank. I had the sending/ pump unit replaced and is still doing it . What else is there
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Answered in 4 minutes by:
3/21/2018
Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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The fuel level sensor is an input to the engine computer, so if this were in my shop, I'd be looking at how the ECM is seeing this input. Is the ECM seeing low fuel level, or is it seeing the actual fuel level but then sending out erroneous information to the rest of the vehicle? The scan tool really hold the keys to this diagnosis. The fuel level sender in the tank is not connected to the gauge in any way, the ECM reads the fuel level data, then sends a message to the cluster telling it what the fuel level value is, and the cluster has the job of running the gauge based on this information.

I wouldn't diagnose this without a proper scan tool. You've already spent a good chunk of money on a fuel pump that you didn't need, I wouldn't put any more money into parts, I'd pay a mechanic the $85 or whatever he wants to get a good scan tool on it and diagnose it.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. If you need more help, just let me know, I am happy to follow up.

Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
Verified
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Jerry Newton
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