How do you wire a GM flex fuel sensor for an LS swap?
It's a three-wire sensor: ground, battery power and a frequency signal (CPR Racing).
- Signal: the ethanol percentage is sent as a frequency. The computer supplies a 5 V pull-up on the signal circuit and the sensor pulses it to ground. Normal readings are about 50 Hz (0% ethanol) to 150 Hz (100%).
- Computer input: it has to go to an input that can read frequency. On a Holley Terminator X, that's one of the frequency-type inputs (Texas Speed).
Confirm the connector pinout from your sensor's instructions before wiring. See fuel, E85 & boost.
Confidence: medium — sources disagree or are limited; check the sources below.
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Sources
- Flex Fuel Sensor GM/Continental OEM E85 — CPR Racing
- Holley TERMINATOR X MPFI, LS1 — Texas Speed