Car Electronics: OBDII information

SAE standards specify that each group of bytes sent to the vehicle must adhere to a set formant. The first byte (known at the 'mode') always describes the type of data being requestied, while the second, third, etc. bytes specify the actual information required (given by a 'paramameter identification' or PID number). The modes and PIDs are described in detail in the SAE document J1979 (ISO 15031-5), and may also be expanded on by the vehicle manufacturers.
Source: ELM Electronics ELM323 Datasheet
 
Bump.

I KNOW its possible to get the Fuel Level over WDS, just asked the Mazda tech. It reports back the % remaining in the tank. I really would like to read this over my ELM232 based OBD II board so i can put it on my carputer.

There HAS to be a PID for this, and other sensors. There has to be a way to get this info. I tried doing a freeze frame, hoping it would return all sensors, but it returned with NO DATA, which is quite gay...could be my ELM chip though, v1.1 or something, they have 2.0 now which is much better...

Unless the WDS is some super mega gay system with Uber proprietary encrypted datatransfers...(Standards do require any uploads to the ECU via OBDII to be encrypted. I think the WDS machine is just a big OBDII plus Mazda encryption to upload maps and whatever..) BUT why would stuff like MAF and Intake Temp be able to be read, but not fuel level. there has to be a PID.

Bottom line, how do we go about finding it?
 
Also, is this site
http://www.mazdatechinfo.com/
worth it? i will buy the 24 hour thing if they will have the PID codes but it can't imagine them having them. There has to be a way to scan the bus for available PIDs...grrrr...This is the irritating part of owning a Mazda that ISN'T an RX-7 or Miata :mad:

back to google.
 
Eh, **** it. I wont be able to get it. I can only get manufacturer specific trouble codes, but i guess the fuel level s*** is propreietary. how ******* gay.
 
this is getting interesting.(even if im only talking to myself)..kinda...apparently these ECUs use the J2534 standard...which means they can be programmed WITHOUT the WDS....
 
The proper connector is defined as SAE J1962 (with FEPS).

FEPS: Flash EEPROM Programming Signal. 18 volt DC signal sent by the scan tool to initiate PCM reprogramming.
 
yea i'm pretty lost as well. but i think you are trying to figure out how to get your carputer to display the data from the sensor already on your car that are being fed to the ECU. such as the fuel tank level. please let me know if that is correct. and either way, what exactly are you doing???
 
well im not sure but im almost positive that shop scanners can check all of these things. Id say check into snap-on and see if you can borrow.
 
pb4ugoout said:
yea i'm pretty lost as well. but i think you are trying to figure out how to get your carputer to display the data from the sensor already on your car that are being fed to the ECU. such as the fuel tank level. please let me know if that is correct. and either way, what exactly are you doing???

yeah im trying to get the fuel level (from stock fuel level sender) over OBDII but i dont think its gonna happen...i want to be able to put automatic MPG calculations on my screen.
 
SenorCorwin said:
well im not sure but im almost positive that shop scanners can check all of these things. Id say check into snap-on and see if you can borrow.

well the damn mazda WDS can check it too but does not provide the actual PID but i think because maybe its not on the OBD bus but on the J2534 or whatever crap. Only a certain number of sensors are mandated by the SAE, the other ones, like fuel level, can be implemented however they want. Im talking to a guy who got the fuel level sensor on his Focus, so im hoping maybe it will be the same since we are the goddamn bastard children of Ford :(
 
the only thing i can think on obd is fuel trim... that tells if its lean or not.

so you maybe correct i havent looked at a obd in a while.
 
dex i got a q for you - if you look at the generic OBDII scanner i just bought from eBay it says if you cycle the codes 5 times it clears the CEL. so surely there is a signal or wire that can be tapped to turn off if not eliminate a CEL without resetting the comptuer and getting poopy milage and losing your presets etc etc. even possibly something you coudl do to prevent it from coming on.

so for example if i have a constant CEL due to EGR being plugged up on aftermarket kit, maybe a switch or resister that could shut off at the flip of a switch a CEL or soemthing to prevent it all together.

for some reason i think that i am getting a CEL which is causing me to lean out under boost for whatever reason. reason i think this is because i can reset the comptuer and it works, then about 60 miles later its lean again.
 
It actually sends a data command to the ECU to clear the code.
clearing.jpg
 
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