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Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » Confusing Air/Fuel sensor readings

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Author Topic: Confusing Air/Fuel sensor readings
dnmonin
Member
Posts: 3
Post Confusing Air/Fuel sensor readings
on: January 6, 2020 (GMT)

I’ve been using Torque App to get sensor information from my Toyota Corolla 2014. Most of the sensor readings make sense. I must say that the car runs fine. I just want to create a baseline in case the car develops an issue sometime down the road. Anyway, most of the readings (such as RPM, MAF, MAP, IAT etc) look reasonable. But I find the pre-cat Air/Fuel sensor readings pretty confusing. My car has a wide-band Air/Fuel sensor. Its voltage is supposed to stay around 3.3V and not move much. And this is what is observed most of the time. But sometimes the voltage goes up to 5V and flattens there (stays at 5V). Typically this happens when, with the car moving, I suddenly release the accelerator peddle. The voltage goes back to 3.3V as soon as I press the peddle again. I’ve also looked at the Equivalence Ratio. It does a similar thing. Most of the time it’s around 1, but when the accelerator peddle is released (with the car moving) the ratio goes up to ~1.23 and flattens there. Goes back to 1 when the peddle is pressed again. Does anyone know why this happens? This behaviour is not observed when the car is stationary.

moreause
Member
Posts: 509
Post Re: Confusing Air/Fuel sensor readings
on: January 6, 2020 (GMT)

when you release the gaz pedal
afr goes into the roof 20 + instead of the standard 14.7 for gazoline

these days for fuel economy they even shut the injector down for a while, until the rpm drop to much and fuel is needed to make the engine run

PS just check what is the value in hard acceleration … afr goes down in acceleration …

dnmonin
Member
Posts: 3
Post Re: Confusing Air/Fuel sensor readings
on: January 7, 2020 (GMT)

That is what I thought too. That the equivalence ratio would go up to >1.4 (20+ / 14.7) but it peaks at ~1.23 instead (18:1). I’m wondering if there is maybe a scaling error somewhere in Torque App calculations.

afr does go down in acceleration. It goes down to 0.8-0.9. I haven’t tried full open throttle though.

I found a Toyota afr voltage chart. According to the chart 4V corresponds to 19:1. I’m getting 18:1 at 5V. Should be more than 20:1 if one extrapolates the table. Something is not right here.

AFR voltage OEM PID Air/Fuel Ratio
2.4V 12.00A/F
2.8V 13.20A/F
3.3V 14.70A/F (stoichiometric ratio)
3.6V 16.50A/F
4.0V 19.00A/F

Capp777
Member
Posts: 2862
Post Re: Confusing Air/Fuel sensor readings
on: January 7, 2020 (GMT)

Just curious what pid are you using?
and its hex response.

Maybe you should make your own
custom pids to correct differences.

Torque is probably using standard
scaling and maybe your vehicle
requires a modified scaling for
proper results.

dnmonin
Member
Posts: 3
Post Re: Confusing Air/Fuel sensor readings
on: January 8, 2020 (GMT)

PID: 24 — O2 Sensor1 Equivalence Ratio
PID: ff1240 — O2 Sensor1 wide-range Voltage

Is there a way to see if there is any math transformation involved when showing these PIDS in Torque? Or what I’m seeing is what Torque is getting from the ECM?

Capp777
Member
Posts: 2862
Post Re: Confusing Air/Fuel sensor readings
on: January 8, 2020 (GMT)

Create your own custom pid for
0124 and test for the hex response
in the pid editor while connected.

Search web for Wiki OBDII PIDs.

Are you sure your volts reading is
not using a modified scaling too?

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