Flex fuel questions for those with flex fuel kits and Hondata.

[1981CBX]

The P0128 CEL is saying your thermostat isn't reaching normal operating temperature. If you put an aftermarket thermostat (which is snake oil and totally pointless, mind you), it is expected to throw this CEL.

The CELs caused by flex fuel are different and have to do with having a significantly different temperature between ECT1 and ECT2 on a cold startup. Because your flex fuel kit is plugged into ECT2, it will usually read completely differently and thus throw the CEL... but not P0128.

good information and it makes sense, but my situation is slightly different.

1) The thermostat is working correctly.

2) The thermostat is the one that came over on the used engine which is now propelling my car.

3) during the engine swap I never had to remove any of my E85 flex fuel kit except for the fuel line which was reconnected as a fuel line.

4) before my engine blew at Thanksgiving the car passed an emissions test when tuned for Hondata’s stock Honda tune.

5) once I clear P0128 In the morning, I can drive all day stop and start shut it off start it up and no DTC. Let it sit overnight, boom DTC

6) The flex fuel kit is plugged into the radiator sensor which would be ETC. so my ECU is detecting the flex fuel kit as the ETC error, but only in the morning.

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[kefi]

good information and it makes sense, but my situation is slightly different.

1) The thermostat is working correctly.

2) The thermostat is the one that came over on the used engine which is now propelling my car.

3) during the engine swap I never had to remove any of my E85 flex fuel kit except for the fuel line which was reconnected as a fuel line.

4) before my engine blew at Thanksgiving the car passed an emissions test when tuned for Hondata’s stock Honda tune.

5) once I clear P0128 In the morning, I can drive all day stop and start shut it off start it up and no DTC. Let it sit overnight, boom DTC

6) The flex fuel kit is plugged into the radiator sensor which would be ETC. so my ECU is detecting the flex fuel kit as the ETC error, but only in the morning.

It may seem to you that it’s operating properly, but if it’s giving you that CEL it means it’s not operating within the specifications the ECU expects. It’s a very specific CEL. Does it pop immediately upon starting the car or does it take a few minutes?

Flex fuel plugs into the radiator’s coolant sensor which the ECU doesn’t look at for thermostat performance.

Perhaps the engine you bought had an aftermarket thermostat on it?

If you have to disable an emissions related CEL you won’t be able to pass emissions, no way around that.

I know this is a separate issue, but don't you also have to change the voltage scale with the PRL kit because it is different than what Hondata expects to see?

There's a section for specifying the voltage and every kit has something different. I’ve recently heard the Hondata basemap doesn’t use the right values but I haven’t got a concrete answer yet on what the PRL kit range is supposed to be.

 

[1981CBX]

It may seem to you that it’s operating properly, but if it’s giving you that CEL it means it’s not operating within the specifications the ECU expects. It’s a very specific CEL. Does it pop immediately upon starting the car or does it take a few minutes?

Flex fuel plugs into the radiator’s coolant sensor which the ECU doesn’t look at for thermostat performance.

Perhaps the engine you bought had an aftermarket thermostat on it?

If you have to disable an emissions related CEL you won’t be able to pass emissions, no way around that.


There's a section for specifying the voltage and every kit has something different. I’ve recently heard the Hondata basemap doesn’t use the right values but I haven’t got a concrete answer yet on what the PRL kit range is supposed to be.

 

[Centripetal]

@1981CBX Can you post your calibration so we can check the settings? Any cooling system mods like reverse hoses?

ECT1 measures the temperature of the coolant in the engine.

Normally (without flex fuel modification), ECT2 measures the system coolant temperature. It is generally used to control the fan because when ECT2 value is elevated considerably above ambient, the thermostat is open and coolant is flowing through the system.

The MIL you've mentioned means the ECU has detected a rise in ECT2 and the temperature of ECT1 is less than 75°C.

With the flex fuel modification, the ECU is using ECT2 to measure ethanol content. If set correctly, Hondata's calibration works around the thermostat stuck open check and the fan control.

If your objective is to pass emissions, just hook ECT2 back up and re-enabled the check. Drive the car a few times enough to warm up. Take emissions test. Then switch it back after you pass.

 

[1981CBX]

Hondata flex fuel tune cleared everything up.

 

[1981CBX]

@1981CBXIf your objective is to pass emissions, just hook ECT2 back up and re-enabled the check. Drive the care a few times enough to warm up. Take emissions test. Then switch it back after you pass.

but I didn’t have to do that last time. This is the puzzling thing. I’ve had the flex fuel kit on the car since new, and now I’ve gone through one omissions test by merely putting the stock base tune on. That being said, I put the E 85 tune on yesterday and this morning it started up just fine without a DTC code. We’ll see how it goes from here on out it’s another year and a half before I have to do omissions again

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