l Open or short in FF sensor VPWR circuit
l Open in battery ground to FF sensor circuit
l Open in FF sensor signal circuit
l Short to ground in FF sensor signal circuit
l Fuel contamination
l Short to VPWR in FF sensor battery ground circuit
l Short to VPWR in FF sensor signal circuit
l Fuel separation
l Damaged FF sensor
l Damaged PCM
Guess piece of black tape over Check Engine Light... What happens if I just unplug it.?
I don't really know. My guess is that you would be OK. The flex fuel sensor generates a signal with a frequency that depends on the amount (%) of ethanol in the fuel. The more ethanol, the higher the signal's frequency. I would assume that an unplugged sensor would generate no frequency, as if there is no ethanol in the fuel. I've never heard of a "failure mode" for the flex fuel sensor, so that's why I would assume that the PCM would treat the situation like that.
I'm just hypothesizing here, though, so don't go relying on what I'm saying without reading or hearing more on the subject.
DO NOT unplug that sensor. I had the same exact problem with my truck and unplugging the sensor causes the truck to stall at random.
I found this out a couple weeks ago when my 1999 Ranger XLT decided to stalled on me (and about every mile or so thereafter). When I diagnosed it, the code P0176 came up so I decided to do some investigating. It turns out that the flex fuel sensor is mounted directly underneath your driver's seat in the left frame rail. This sensor connects to a wire harness that mounts to the frame rail on a plastic bracket. Somehow something must have kicked up and hit mine because the bracket was broken causing the connector for the flex fuel sensor to become disconnected. Long story short, I plugged it back in and the truck ran fine for a week. 3 days ago though, the MIL light came back on...flex fuel sensor malfunction. I figure that the intermittent connection of the loose cable caused the sensor to fail after all. This is normal for any electronic device, try unplugging and plugging in a computer very rapidly for about a minute and you will see what I mean. Now that the faulty sensor is actually plugged in my truck runs fine BUT the MIL light is driving me nuts. I am working on a way to replace this sensor without paying the $454.00 list (that's rediculous). A simple microcontroller should do the trick for MUCH cheaper if I generate a fixed frequency. A friend of mine provided me with the proper frequency table so the plan is to fix it at a good one and go about my business. Hope this helps...good luck.
DO NOT unplug that sensor. I had the same exact problem with my truck and unplugging the sensor causes the truck to stall at random.
I found this out a couple weeks ago when my 1999 Ranger XLT decided to stalled on me (and about every mile or so thereafter). When I diagnosed it, the code P0176 came up so I decided to do some investigating. It turns out that the flex fuel sensor is mounted directly underneath your driver's seat in the left frame rail. This sensor connects to a wire harness that mounts to the frame rail on a plastic bracket. Somehow something must have kicked up and hit mine because the bracket was broken causing the connector for the flex fuel sensor to become disconnected. Long story short, I plugged it back in and the truck ran fine for a week. 3 days ago though, the MIL light came back on...flex fuel sensor malfunction. I figure that the intermittent connection of the loose cable caused the sensor to fail after all. This is normal for any electronic device, try unplugging and plugging in a computer very rapidly for about a minute and you will see what I mean. Now that the faulty sensor is actually plugged in my truck runs fine BUT the MIL light is driving me nuts. I am working on a way to replace this sensor without paying the $454.00 list (that's rediculous). A simple microcontroller should do the trick for MUCH cheaper if I generate a fixed frequency. A friend of mine provided me with the proper frequency table so the plan is to fix it at a good one and go about my business. Hope this helps...good luck.
Good stuff BiG_AnT. Thanks for passing along the info, and welcome to FTE!
Let us know how the microcontroller mod works out.
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