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Calling all pro obd1 tuner experts... I found something interesting!

dbrannon79

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I just found a new setting in the bin file for high idle. at first I thought there were two, but now I found another. I know on the OBD2 systems there is three settings and from what I have been told there is only 1 for OBD1. I just found 3 in the OBD1 prom chip. need to verify this, I also don't know if the labels on the "PTO" in gear and in park are correct since the XDF was hand made by someone.

it is possible that there may be another pin or two on the PCM that can be wired in to a switch to have all three options. I will need to study that as well. here is a screenshot with their hex offset locations in the bin file. note: I have changed two of them so that I can test my high idle switch and see what RPM it goes to.

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dbrannon79

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Yeah, honestly I am just comparing definition files in tunerpro. I found one online for our 6.5's that most everything it measures is in metric. then look at each setting and see what data location it's pulling the info from in the same prom bin file. so far all the fuel, timing, and trans info match, but there are a few like the high idle and such that are different. the definition I found this one from also has the PTO settings that match but has this one additional setting in there.
 

dbrannon79

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Here is a good discussion topic on the TCC apply and release setting. notice that 2nd gear TCC lockup is active when trans is in "HOT" mode.

I am thinking if someone wanted to allow TCC in 2nd gear, they could just change the trans temp mode or copy the hot mode tables into the normal mode tables below. not sure how different the truck would feel on the road allowing TCC in 2nd gear.

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alex1234

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each definition file (*.XDF) works only for some chip, not for all.
i have some. worked for mine BRMM chip
also ADX file for real time data on tunerpro or other app.
those file permited me to: complete disable EGR, and turbo boost issue and related defueling.
XDF leave some item not defined, so not all was defined.
you can enable or disable all you want, also flags for DTC
disable the top speed limiter, etc, ect...
you must pay attention on what you are working and changing
 

WarWagon

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Be interesting to follow the logic of WOT held in 3rd gear towing ~60 MPH. Would be a min or two before the TCC would apply on my 1993. Figured trans heating up locked it. One of the worst feelings of an engine falling on it's face ... Rev up and no power to be reving up due to the turbo and exhaust restrictions.
 

dbrannon79

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Just ran across this TSB that shows a table of what eprom chips that should be is certain trucks. looks like I will be on the lookout for GM part number 16244781 BXPW chip to start tuning with. I am curious as to what updates GM did with this chip. looking on OEMcats dot com shows this is the latest one for the truck I am running.
 

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dbrannon79

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I haven't updated anything on this thread for a bit, I though I'd share what I have found and learned.

I had been in contact with Lyndon at Westers Garage on his definitions for CATS tuner software. I had emailed him about helping me locate the updated prom that GM issued back in 1996 that replaced BPAA. the BXPY. out of the blue he gifted me with the stock bin file I was looking for. I think from what I have found, this is one of the last obd1 PCM updated that GM issued for these trucks.

I have since added some changes to the fuel, boost, and glow plug times. changed both the PTO idle setting, one for in park and the other for in gear. both respond . I set the PTO idle to 950 in park and 750 in gear. flip the high idle switch and it works flawlessly!

the changes I have been able to find that GM did was increase the line pressures in the transmission. there are other changes in the bin that the XDF file (definition) does not tell me what they are. But I have been running it and have noticed a smoother shift between gears. faster take off, and also noticed that all the tables related to throttle position seems to be engine load.

my boost pressures at a hard take off will climb up to right at 13psi ( I had set to be max) and once the desired speed is reached the pressures will slowly drop to zero. while cruising at freeway speeds. even while cruising, when I reach an incline, the boost pressures start coming back up due to engine load even though my foot hasn't moved on the pedal. this should save some on fuel mileage :)

other than the issue i have posted about in the other thread which I think is an injector making some noise, it runs smooth with much better power than stock. my TDCO is set to -0.67 right now and I have not changed anything in the tune for timing.

on the definition file I have for tunerpro, I have been able to modify some items making it more accurate for tuning changes, also for data logging.

not to mention I am using a PCM from a 94 truck after I found out that my PCM wouldn't respond with controlling the wastegate solenoid. I almost ordered a new solenoid when just for the heck of it I plugged in the PCM I got from the junkyard and it worked and responded. with the original PCM I was also having minor issues data logging with tunerpro. split second connection drop out's. with the 94 PCM I have no problems!
 

NVW

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Years back I seem to recall 3 high idle settings for OBD-1, I think if you used one (of two), switch's you would get 1050, switch the other and it would be 15-1600? Switch both and you would get 1800?

I have 2 chips for OBD-1, one has high idle set at 1050 (Westers), the other (Dennis') is that 1800 range. This happens with the high idle switch I put in myself, the tune are what determine the rpm. Stock chip was also 1050 with my switch.
 

dbrannon79

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that was what mine was set to as stock. in the definitions I found three settings. one is labeled as "High Idle" the other two are "PTO Idle" when I wired in the switch I only found one pin on the PCM in the diagram that I can connect to. I would like to find where to connect to for the other. I did try changing the RPM setting for all three just to see how it responded with the wired in switch. when the switch is on I am getting the PTO setting I used.

with the switch on and in park, it will run at 950 which is what I set in the tune. as soon as I drop it in gear it automatically jumps to the lower setting in the tune.
 

dbrannon79

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I would have to go back the the forum post where I found how to wire it in, but iirc the switch when on sends 12v+ to the one pin in the PCM for the PTO idle to be on. I know in the connector there are other pins that aren't used, I will need to look over the diagram and the pinout for it and see what the unused pins are for.
 

dbrannon79

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yeah those old links are gone. from what I have gathered reading here in the forums those links showing "dieseltowingresource" is what this forum was called then. I wonder if BoostN might be able to revive them in a archive here for us.
 

dbrannon79

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yes, that is the forum thread I when by. but OBD1 only has one setting :( mine is a 95. but in the tune for obd1 it does show settings for three. on the stock tune all three were set at 1050.
 

dbrannon79

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this is the only PCM wire schematic I have. shows for a 1995 vin S but doesn't show all of the connectors. only connectors "C" and "D" nothing for "A" maybe someone here has a complete one for 94-95 vin F in their library.

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dbrannon79

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I found a shop manual for vin S, P and F with diagrams, but nothing in there for high idle or PTO. even in the connector pinout shows pin A6 (unsed for high idle mod) shows "Not Used" I need to find a diagram for the truck application that had these options installed as factory to see if there are other connector pins that use these settings in the tune.
 
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