Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

Switching from M6 codes to A4 codes

Old 07-18-2011, 05:01 PM
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Switching from M6 codes to A4 codes

Ok so i was wondering if there was a program that i could use to delete the M6 interface codes out of my 95 z28 and upload the A4 interface codes. i have the ALDL cable that works for the obd1 and has the 16 pin specifically made for the 95z28. if there is a program out there please let me know. my speedometer is reading 2.35x that actual speed that im going and need it fixed.

I have the Digital Dakota SGI-5 that Injuneer recommended but i would rather try to find a program to use to do this before i start or get someone to start cutting up/splicing wires to my VSS.

Thanks in advance.


Jason
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Old 07-18-2011, 05:21 PM
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Re: Switching from M6 codes to A4 codes

Install the A4 program, and program out all the tranny codes.
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Old 07-19-2011, 09:51 AM
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Re: Switching from M6 codes to A4 codes

Which program should I use to do this?
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Old 07-19-2011, 12:43 PM
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Re: Switching from M6 codes to A4 codes

Easiest thing to do would be to send it to a mail order programmer, and have him make the changes.
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Old 07-19-2011, 12:46 PM
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Re: Switching from M6 codes to A4 codes

Tunercat should be able to do what you want. http://tunercat.com
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Old 07-20-2011, 06:22 PM
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Re: Switching from M6 codes to A4 codes

i downloaded that and it was giving me a hard time having to do all this stuff to get it to work since i have Vista. now that its downloaded what do i have to do to get started?

And would switching PCMs work? meaning just take a 95 z28 pcm programmed with A4 codes and putting that in my car?
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Old 07-20-2011, 08:24 PM
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Re: Switching from M6 codes to A4 codes

I think i will just do the email tune through madz28 if i cant get the Stock tune file for the 95 z28 A4.
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Old 07-20-2011, 08:33 PM
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Re: Switching from M6 codes to A4 codes

You need the definition files first. Download them from Tunercat. You need the EE files. You'll have to pay for them but you can use the Tunercat program free for a while. After you get them read your PCM. Save that file and use tunercat to modify it. Be sure to save a stock version also. Since you have a TH350 it looks to me like all you need to do is turn off anything that has to do with the transmission. I'm at work so I can't look at the program but I think all that is under the switch menu. Then you can use the tools menu to try to fix the speedometer. You will probably just have to play around with the tool to get it right. If I remember correctly the number of pulses for the auto trans is 40. I would start there since the T56 is different. I don't know if your trans is the same as a stock auto. The other entries in the speedometer tool are self explanatory. Once your program is modified you need to program the PCM. When you program it make sure your battery is charged (the car and PC) I always keep my PC plugged in, not just on battery. Once the programing starts it must finish or you can fry your PCM. If you're not comfortable doing it I would send it to a programer as suggested above.
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Old 07-22-2011, 04:48 PM
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Re: Switching from M6 codes to A4 codes

Update:

So i got tunercats to work. I ordered the $19.99 $EE definition file and got it to load with TC. So i read the PCM with it and i was trying to figure out how to get my speedo to not read 2.35x the actual speed. i saw the speed calibration section under Tools and i change the tire size to what i had and put the rear end ratio to 3.42:1 and the Sensor Pulses/Driveshaft Rev to 40 and i click calculate and Apply. so i updated the PCM in my car and went out with a buddy driving beside me at 20 mph and what did my Speedo say? it said 20 mph. This was my first try ever with tuning myself and messing with tunercat and i have to say i did good for the first try by getting my Speedo to read Accurate.

Thanks everyone who helped me with this. now i have to figure out how to program the Bolt-ons that are on my car into the pcm. or does it not matter if i have long tubes, 52mm throttle body and CAI?

Last edited by Bykerboy869; 07-22-2011 at 10:20 PM.
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Old 07-23-2011, 06:34 AM
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Re: Switching from M6 codes to A4 codes

Those three mods don't make a big difference as far as the tune, but you could pick up 10-15HP even if it was totally stock. The normal approach is to lean out the overly rich target A/F ratio that the PCM calculates in power enrichment (PE) mode (= WOT). That's where the HP gains come from. You might also want to install a 160*F thermostat, and lower the fan on/off temps. Then play with the ignition advance to see if you can add a little advance without causing knock retard.
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Old 07-23-2011, 11:54 AM
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Re: Switching from M6 codes to A4 codes

I already have the 160 t stat installed in the car.

So im at the Fan Enable Coolant Temp(Deg. C) VS. Speed

Fan 1s low MPH is 107.75 and High MPH is 107.75
Fan 2s low MPH is 113.00 and High MPH is 113.00

What is the typical change to them that is done with having a 160 T-stat.

And for Leaning it out I should do a Diagnostic scan to my car before messing the the AFR correct?
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Old 07-23-2011, 12:44 PM
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Re: Switching from M6 codes to A4 codes

Not sure what the diagnostic scan is going to ell you, unless there is evidence the PCM is struggling with the long term fuel trims to keep it running at 14.7:1 in closed loop. Once you go WOT, the only thing you will notice is the target A/F ratio (what it is shooting for, not what it is actually achieving) that is not read by all scanners, and you could look at the O2 sensor readings to see if its running grossly rich or lean, but the stock narrow band sensors are simply not reliable at the typical A/F ratios used for peak power and peak torque.

Ideally, you would use a wide-band sensor to determine where it is now at WOT, and how much correction you want to shoot for. Then check the results. Remember, there is no "magic" correct A/F ratio. It's a balance of A/F ratio and ignition timing, and how much of a cushion you want to prevent the possibility of knock retard.
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