Flex Fuel Sensor calibration in ECM

Scargoes · 05-30-2026, 06:59 PM

I have a 2020 RS with the 2.0T with a tune including e85 from ZZP. The E content never goes above 74-75% in the HPTuners logs or on the Banks iDash display. I have measured the E content with one of those test kits and it shows 85%. I thought I might have a bad sensor and got a new one but it reads the same. I did a quick test with my other Camaro and the system is showing 84-85% with the new sensor plugged into the car and the test fuel in the sensor, but then in the RS it drops back to 74-75%. I thought there might be a cap on the max content reported but there is no option in the RS tune file for adjusting that similar to my 2018 SS 1LE tuning file. Does this display actually mean anything? Is what is displayed the same info used by the ECM for fueling/advance tables? My thoughts are that if the ECM is displaying 75% when its actually 85%, it would be targeting less fuel and timing making it more prone to knock and possible engine damage. I realize the O2 sensor is there to help but the lambda readings are a bit leaner than targeted. Is there any way to get the ECM to display the true E content? Or am I just being too picky about it. FWIW, the tuner at ZZP didn't seem to have issue with the 10% lower display that the test kit showed.

KingLT1 · 05-31-2026, 08:21 AM

There is a setting in the calibration for how much Ethanol content the sensor can read. You might check and see if that is where it's being limited. There is likely no timing difference between E75 and 85. If the wideband doesn't show leaner than commanded, then it's a non-issue.

Scargoes · 05-31-2026, 04:25 PM

Yeah, the option to change the ethanol content in the tune file is missing on the RS tune file but it is present in the SS tune file. I don’t know why it is missing for the RS. And the commander and reported lambda values are off. The reported is .01 to .02 off the commanded value toward the lean side(ie. commanded .826, reported .835).

Megahurtz · 06-01-2026, 08:17 AM

Some sensors seem to read inaccurately above 75%. Never did figure it out exactly. The DSX sensor reads differently than the Continental vs the GM one depending on when it was manufactured. I usually have full timing in by E70 anyhow so it doesn't matter what the sensor reads past E70. As long as the car is tuned properly and reaching the desired lambda, just send it and don't worry about it.

Scargoes · 06-03-2026, 10:53 AM

Thank you guys. I won’t worry about it any more.

05-30-2026, 06:59 PM	#1
Scargoes Drives: '18 Hyper Blue 2SS1LE '20 Crush RSR Join Date: Aug 2018 Location: Dessert Posts: 523	Flex Fuel Sensor calibration in ECM I have a 2020 RS with the 2.0T with a tune including e85 from ZZP. The E content never goes above 74-75% in the HPTuners logs or on the Banks iDash display. I have measured the E content with one of those test kits and it shows 85%. I thought I might have a bad sensor and got a new one but it reads the same. I did a quick test with my other Camaro and the system is showing 84-85% with the new sensor plugged into the car and the test fuel in the sensor, but then in the RS it drops back to 74-75%. I thought there might be a cap on the max content reported but there is no option in the RS tune file for adjusting that similar to my 2018 SS 1LE tuning file. Does this display actually mean anything? Is what is displayed the same info used by the ECM for fueling/advance tables? My thoughts are that if the ECM is displaying 75% when its actually 85%, it would be targeting less fuel and timing making it more prone to knock and possible engine damage. I realize the O2 sensor is there to help but the lambda readings are a bit leaner than targeted. Is there any way to get the ECM to display the true E content? Or am I just being too picky about it. FWIW, the tuner at ZZP didn't seem to have issue with the 10% lower display that the test kit showed. __________________ 2018 Hyper Blue Metallic 2SS 1LE with Nav, PDR, and track alignment 1:28.95 Willow Springs Big Track

05-31-2026, 08:21 AM	#2
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 7,707	There is a setting in the calibration for how much Ethanol content the sensor can read. You might check and see if that is where it's being limited. There is likely no timing difference between E75 and 85. If the wideband doesn't show leaner than commanded, then it's a non-issue. __________________ 2016 NFG SS A8/Whipple 2.9/Fuel System/Flex Fuel

05-31-2026, 04:25 PM	#3
Scargoes Drives: '18 Hyper Blue 2SS1LE '20 Crush RSR Join Date: Aug 2018 Location: Dessert Posts: 523	Yeah, the option to change the ethanol content in the tune file is missing on the RS tune file but it is present in the SS tune file. I don’t know why it is missing for the RS. And the commander and reported lambda values are off. The reported is .01 to .02 off the commanded value toward the lean side(ie. commanded .826, reported .835). __________________ 2018 Hyper Blue Metallic 2SS 1LE with Nav, PDR, and track alignment 1:28.95 Willow Springs Big Track

06-01-2026, 08:17 AM	#4
Megahurtz Snackbar Tuning Drives: 2023 SGM ZL1 Join Date: Oct 2016 Location: Florida Posts: 1,525	Some sensors seem to read inaccurately above 75%. Never did figure it out exactly. The DSX sensor reads differently than the Continental vs the GM one depending on when it was manufactured. I usually have full timing in by E70 anyhow so it doesn't matter what the sensor reads past E70. As long as the car is tuned properly and reaching the desired lambda, just send it and don't worry about it. __________________ GM Gen V Calibrator

06-03-2026, 10:53 AM	#5
Scargoes Drives: '18 Hyper Blue 2SS1LE '20 Crush RSR Join Date: Aug 2018 Location: Dessert Posts: 523	Thank you guys. I won’t worry about it any more. __________________ 2018 Hyper Blue Metallic 2SS 1LE with Nav, PDR, and track alignment 1:28.95 Willow Springs Big Track

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