Turns out that there is a 1D table that overrides the periphery settings in P2 FCA and P3 FDA and sets all these bits equal to zero. This would disable nearly all of the OBD-II tests, however, I'm not sure if it will kill off all associated CELs. Would be interesting to try on a car with none of the OBD CEL kill tricks.

<table name="Disable/Allow P2_FCA, P3_FDA Bits" category="Periphery" address="101C" type="1D" level="2" scaling="uint8"/>

 

I dont have any mods to my rom and have a CEL for the rear o2 being out and replaced with a wideband. will this work with rom 94170008? Also is there any bad effects that will come along with it?

 

hey i have a bunch of cels and i only disabled the rear o2 and the things to aid with cold start up. but i still have a few more cels would you like for me to still try?

 

ok i tried the patch and it worked for all but the p0141 o2 sensor heater, which i havent done the resistor mod yet so i was thinking that was gonna happen. Thankks for all the hard work once again.

 

mrfred: I mentioned 101c over here (and as usual, acamus was there long before us) when I was working my way through the periphery ROM-to-RAM copying routine; there's a whole bunch of items just past 0x1000 that control a variety of periphery bits.

 

I was thinking about you mentioning something like this when I put up the post, but I couldn't find it. Did you try out disabling 0x101C?

 

just for clarification, this would mainly be used to pass emissions tests, correct? not intended for noobs that want to disable their CEL...

 

I never bothered running through any tests of it, since the code seemed pretty clear, albeit somewhat odd; it seemed really weird to have multiple places to enable/disable those, especially the individual FCA toggles from 101D-1025. I think this is one of those places where it would be a lot more obvious if we had the original C source sitting in front of us with comments (and a window with Google Translate running in it ).

(At this point, I can't actually test much of anything either, which is why I've been so quiet lately; the recent cold weather caused some damage to the Evo that I haven't wanted to investigate both because of the cold and because I'm afraid of what I'll find. I have this sinking suspicion that I may have our 1g up and running with an IX ECU before I have the Evo running properly again...)

 

Anyone who tried this patch, do you still have normal MUT and OBD2 communications?

Setting Periphery2 bit 0 = 0, looks like it will lock out 15625 and 10400 baud selection under certain conditions.

Unless I am looking at things wrong.


Edit :
Periphery2 bit 0 = 0, looks like it could mess with the Front O2 Sensor Switch Point, also.

Maybe some else could look at Periphery2 bit 0?

 

Looks good Mrfred, I assume the xml works for all the popular rom ID's? When I finally get my CEL throwing evo ecu'd DSM up and running next weekend I'll give this a shot. Also I assume I would change the table to all 0's?

 

Turns out that's one of the few tests that it doesn't disable. It also does not disable P0069, P0111, P0554, P1530, P0830, and P0090. These along with P0140 are all controlled by P4_FEA.

For bytes that override individual bits, I thought that these may be different from disabling the corresponding periphery bits because I assumed some of the bytes would appear in throughout the code to disable sections of code that may need to be disabled along with whatever the periphery bit disables. I just checked and its not the case. So much for that though.

Sounds like you think you froze the coolant and cracked the block. Bummer if that's true.

I haven't followed all instances of that bit yet, but the ones that I have indicate that it has something to do with closed loop operation.

Yes, it should work for all ROMs. No need to change any bits in FCA or FDA. This bit overrides anything in those periphery bit locations.

 

Just for reference, trying to get the un-blocked OBD tests:

P0069: ??
P0111: IAT sensor input range
P0554: Power steering pressure sensor
P1530: AC pressure or ignition timing or cam sensor
P0830: ??
P0090: ??

MrFred, does this just block the OBDII tests or does it also have the other effects of changing the peripheries (ie, the cruise timing change for the EVAP bits)?

This is a nice quick solution, but unfortunately it doesn't allow for some tests that we might actually want (I know, hard to believe ). I'm definitely going to use it instead of peripheries if it does not change the actual function of the ECU and only prevents DTC.

 

Some of these tests may only be found on Evo 9s. I think P0069 and P0090 are only on Evo 9s. I agree that there are some tests that are good to keep active. What I find interesting about the global disable is that some of the OBD CELs, such as the rear O2 heater CEL, cannot be stopped just by disabling the rear O2 heater test, so I wonder if the global disable somehow can stop the CEL for those kinds of tests.

 

I am still able to use my scan tool and evoscan as before so communications seems to be good

 

When I set myfred's bit to 0 in a USDM 2003 evo 8 ecu running the JDM ROM I evoscan can not scan my ecu for CEL codes.