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Discussion Starter · #1 ·
Has anyone (or does anyone know of someone) here who has reversed the OBD1 P74 ECU output? or know where i can get this information? Anything and everything helps! Thanks
 

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Discussion Starter · #3 ·
i meant reverse engineered it... sorry.
 

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unfortunately the OBD1 does not do any datalogging. This means, there is no information sent to the service connect for you to read from. Thats why its only 2 or 3 wires, unlike OBDII which is standardized across all manufacturers and does provide data output.

So, if you want to log or monitor what your sensors are doing during operation, you need to buy a device with data logging capability ( some WBO2 kits have limited data logging of sensors ) or you need to buy a stand alone ECU that supports data logging ( like the AEM EMS. )

This is why I don't like taking my car to the dealer. They can't just hook up a scantool and say "yup, your O2 sensors readings are bad. Need to replace the sensor." They just guess and tell you to replace suspect sensors until the problem goes away.
 

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Discussion Starter · #5 ·
I'm pretty sure OBD1 outputs information. where did you get your information?
 

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It outputs scancodes only.

Try searching the web for Honda OBDI scantools, you won't find any that read sensor info. I also asked at my dealership if there is anyway to hook up the scantool on a testdrive to diagnose possible problems with my O2 and MAP sensors. THe dealership said the HoNDA OBDI only outputs the CEL code and allows code clearing. It can read sensors.
 

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Discussion Starter · #7 ·

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Yes, Honda OBDI is proprietary.

That product says:

-Live data parameters from Engine (More than 50 parameters.

It doesn't say what these parameters are, and it doesn't say specifically it these parameters are 'sensor' values.

If it does read sensors, this is news to me and my local dealership because they told me several times their scantools cannot read sensor values from OBDI computers.

I'll try looking for more info on whether reading the sensors is possible.
 

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Discussion Starter · #9 ·
blackaddr im in the denial stage so im trying to find more info haha... ill post if i do find anything.
 

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Discussion Starter · #13 ·
I just wanna make sure i'm not havin some 12y/o tell me off. my experience? minor programming mostly web based (PHP)... that's besides the point. what's your take on datalogging from a honda obd1 ecu? possible or impossible
 

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I'm no expert on ECUs, and while I have a background in computer engineering, I probably still know a lot less about ECUs then MD.

I basically took my dealerships answer as fact when they told me they can't log the live sensor data. Even though I've had the dealership tell me facts about my car that were incorrect and had to point out the correct info in their factory service manual.

Additionally, the service port on a Honda OBDI ECU is a serial interface. I figured, transmitting live data from all the sensors would require either an extremely high data rate or have a very low sampling rate in order to use a serial interface like that. So I figured it wasn't possible and starting looking at other options for logging such as Tech Edge WBO2 or just building my own D/A logger.
 

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Discussion Starter · #16 ·
Normally I'd have no interest in re-inventing the wheel. I wanna know more about the ECU though and I've been interested in interfacing between two serial busses for a while so I figure this'd be a good project. Anyway, if anyone has any info on this type of project please post, thanks!
 
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