Explanation of "Engineering Test Mode" codes?

[phoneman91]

It is possible to get into the "Engineering Test Mode" on the HEC when starting the car with the "reset" button depressed. Then it is possible to step thur numerous displays that are mainly in code. Battery voltage,DTCs and all kinds of other information.

Is there anywhere on the internet that will give the explanation of all of these codes?

 

[Northwind]

Don't have documentation, but a lot of the raw data codes (fuel, temp, etc) appear to be based upon a 0-255 scale which is common in electronics (one byte in hex / binary)
thus 0 = 0 and 255 = max. Generally you will never see the extremes, so a full fuel tank indication is 248ish on my car. I don't know if that's a mechanical limitation of the sender, or headroom intentionally built into the scale.

As for the other codes, no idea

 

[Northwind]

delete the double post