Wanting to *UNDERSTAND* the ANHT_HAC better

I am trying to understand the coding that the ANHT_HAC uses to find out how the ECM enables the error codes. My main area of interest is this: I have a code 33 from a '730 setup after driving for a while even though my MAP and vacuum gage taped to the windshield report nothing out of the ordinary (17inHg from gage, 45kPa from scanner). I understand the documentation in the HAC for switches but I do not want to mask this code--I just want to find out what parameters are shooting it off.

Here is what I am looking at, copied from ANHT_HAC...
I understand L8XXX is the hex location for the code. What I am trying to figure out is if the FCB XX is a reference cell to complete the argument on the same line. This is what I gather from the above. The TPS has to be above 1.9% open for the code to set. Whatever is wrong has to occur for at least 1 second. I have no clue what the threshold statement from above is referring to.

I also have questions as to what L8283 and L8284 are referring to. I checked out Programming 101 and there do not seem to be any conversions for MAP like there are for Coolant Temp, Spark adv. and speed. The argument value is what? What the value being reported to the ECM is or what the ECM calculates from taking the reported ratio and multiplying it by 256? I guess I am getting hung up on the ratio statement.

I am not running a very radical camshaft (214/224, .442/.465, 112) that should make me have to change the error values, but I think if I see where it is coming from, I would be better off. TIA, -Matt-

[This message has been edited by HighHopes85 (edited December 07, 2001).]

 

I'm no expert but maybe I could fill in some blanks. The FCB is the outcome of .85 * 256. That equals 217.6 or 218. The hex value of that is DA and that should be the value at L8283. Also, to me it looks like the TPS has to be less than 1.9% for the code to set. L8283 and L8284 are the ratio values that the ecm is looking for to set off the light or so it seems. If the map value is < .85 of the baro then the light sets. L8283 is the check in park, and L8284 is the check in drive. So does the light set in park or in drive at idle? What is the baro reading? One thing I am not completely sure of though is that these lines aren't really the MAP code checks. These are just the parameters. The actual check routine is somewhere else in the code and that is what you really need to look at, or at least I think it is. If the light is setting while the car is being driven then the parameters above shouldn't help any even if they were changed.

 

Thanks for the jumpstart. It's been a pretty busy week so I haven't had much of a chance to do much yet.

My gut says something is wrong with the header on the ECM where the MEMCAL plugs into. Once the code sets (both at idle in park, idle in drive, and about 10% throttle in drive), I can pull over and apply pressure to the memcal housing. The check engine light goes out, resets, acts up again, and can't make up it's mind.

This, combined with normal vacuum gage and Diacom readings, leads me to believe I just have a bum ECM.

It could be a long 200 nile drive home this weekend Thanks again, -Matt-