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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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WE have an intermitent fuel sensor fault (gauge goes to

Customer Question

WE have an intermitent fuel sensor fault (gauge goes to zero, and then returns sometime later) that causes a check engine light. We would like to get the light cleared, and pass the vehicle sticker inspection before it trips again, but wwe have no idea how many times we have to start, run , cold start etc to get the history ready to pass inspection
JA: Does the light stay on, or does it blink?
Customer: The engine light stays on after the fuel gauge comes back to normal.
JA: What is the model/year of your Chevy?
Customer: 2005 Mercury Sable 6 cylender.
JA: Are you fixing your Sable yourself? What have you tried so far?
Customer: The fix is a new sensor at 500$ plus for parts and labor. Because it is intermittent, and we keep the tank full we don't see it as a safety problem while we drive it and save up for the repair
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 2 months ago.
Category: Chevy
Expert:  Jared D replied 2 months ago.

Good afternoon.

More than likely the diagnosis you received is a bad fuel level sending unit. This is part of the fuel pump assembly on this car.

You are right, it doesn't hurt anything to drive it with a bad level sensor and as long as you keep it filled up it won't leave you stranded. The problem is the emissions test will detect the fault and trigger the code. If you keep it above the level of the burned out portion of the sensor then you should be fine and the light won't come back on.

Something you might try is a good fuel system cleaner. Occasionally the problem isn't with the sending unit, but rather there is carbon buildup on the sending unit in one or two spots that makes the sending unit lose communication. I have seen a good fuel system cleaner dissolve that carbon and make the sensor start working again.

Customer: replied 2 months ago.
Thanks for the response, but it isn't helpful. I understood the mechanics of the sensor, as it has been explained by the mechanic that wants to fix it, and we've tried every cleaner, combination of fuel levels, and so on without finding a pattern or solution. I've had the fuel level system working, cleared the code, and had the fuel sensor fail when I turned the key. Thanks for the effort.
Expert:  Jared D replied 2 months ago.

What exactly is your question? Whether it is safe to drive with the problem occurring, or how to pass the emissions test?

Expert:  Jared D replied 2 months ago.

This process usually requires a little bit of back forth communication to solve the concern.

Customer: replied 2 months ago.
How long the car has to be driven without a fuel system error so that the fault system is in a "ready state" which would allow me to get the re-check for the emissions/ safety inspection
Customer: replied 2 months ago.
Jared, there may not be an answer to this question, as I understand that the reset driving cycle is varied.
Expert:  Jared D replied 2 months ago.

Oh ok. The drive cycle does vary from car to car, but a general rule of thumb is about 3 starts and 20 miles. That means you will start it, drive it about 10 miles, shut it off, start it again, drive it about 10 miles, shut it off, start it again and it should clear all of the readiness monitors. Then the fault won't set again until the sensor goes out of range (the fuel gets low enough to hit the dead spot).

Expert:  Jared D replied 2 months ago.

I can send you each of the drive cycles if you want to run them individually, but basically they boil down to drive it about 20 miles at varying speeds.

Customer: replied 2 months ago.
Thanks again, but I have done similar profiles over a period of a couple of days without a rediness reset. I afraid that the solution is just take the bus until I can fix the sensor. Take care.