What frequency range should the FF sensor output for E85 (85% ethanol)?

According to the chart, 85% ethanol corresponds to an FF sensor output frequency of 105–125 Hz.

What is the expected FF sensor frequency for 0% ethanol (straight gasoline)?

The table shows 0% ethanol corresponds to 40–60 Hz.

What overall FF PID frequency range does the diagnostic check for?

The document asks whether the FF PID is indicating a value between 42 and 145 Hz.

What frequency would a 20% ethanol fuel mixture produce?

The example on the chart states a fuel mixture measured or known to be 20% ethanol will generate an FF sensor output signal with a frequency in the range of 55 to 75 Hz.

How is the chart organized?

It plots FF sensor output frequency in Hz (30–140) on the vertical axis against % ethanol (0%–85% in 5% steps) on the horizontal axis, with a table listing frequency ranges for ethanol percentages from 0% to 85%.

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Ford Flexible Fuel (FF) Sensor Ethanol Output Chart - Frequency vs % Ethanol

Flexible fuel sensor ethanol output chart of frequency versus percent ethanol

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Diagnostic chart relating flexible fuel sensor output frequency in Hz to the percentage of ethanol in the fuel.

AI caption January 2010 · Photo 462 of 579

This document is a diagnostic reference chart titled "Flexible Fuel Sensor Ethanol Output," apparently from a Ford service/diagnostic manual (figure reference A24584-A). It instructs the technician to use the chart to determine the corresponding frequency range for a known percentage of ethanol in the fuel, and asks whether the FF (Flexible Fuel) PID is indicating a value between 42 and 145 Hz. The chart plots FF sensor output frequency (Hz, 30–140 on the Y-axis) against ethanol percentage (0%–85% on the X-axis), showing a nominal linear output line with upper and lower tolerance bands. An embedded table lists expected frequency ranges: 0% ethanol = 40–60 Hz, 15% = 50–70 Hz, 25% = 60–80 Hz, 35% = 65–85 Hz, 45% = 75–100 Hz, 55% = 80–105 Hz, 65% = 90–110 Hz, 75% = 95–120 Hz, and 85% = 105–125 Hz. A worked example explains that a fuel mixture known to be 20% ethanol should generate an FF sensor output signal in the range of 55 to 75 Hz. A reader can use this page to verify whether a flexible fuel sensor's output frequency is plausible for the actual ethanol content of the fuel during diagnosis.

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Frequently asked questions

What frequency range should the FF sensor output for E85 (85% ethanol)?: According to the chart, 85% ethanol corresponds to an FF sensor output frequency of 105–125 Hz.
What is the expected FF sensor frequency for 0% ethanol (straight gasoline)?: The table shows 0% ethanol corresponds to 40–60 Hz.
What overall FF PID frequency range does the diagnostic check for?: The document asks whether the FF PID is indicating a value between 42 and 145 Hz.
What frequency would a 20% ethanol fuel mixture produce?: The example on the chart states a fuel mixture measured or known to be 20% ethanol will generate an FF sensor output signal with a frequency in the range of 55 to 75 Hz.
How is the chart organized?: It plots FF sensor output frequency in Hz (30–140) on the vertical axis against % ethanol (0%–85% in 5% steps) on the horizontal axis, with a table listing frequency ranges for ethanol percentages from 0% to 85%.