Making an offboard for tuning - GM Forum - Buick, Cadillac, Olds, GMC & Pontiac chat

Tuner There's one computer that you can hack without risking jail time: your GM car's PCM/ECM. Find out how.

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Old 01-13-2009, 09:26 PM   #1  
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Default Making an offboard for tuning

I have heard of people with bonnies having problems writing PCMs with tuners while the PCM was in the car, with some DIY directions and a trip to Morad, one of the benefits of living in cleveland , i got it all fabbed up and am proud to say i have had a 100% success rate of writing PCMs

unfortunately i didn't think to take any pictures while making it but heres the end result

here are the connections that need to be made

here is the connector, it is the blue harness from the pcm and the OBDII connector, the 2 wire hanging out are for power

the battery charger i use to power everything, this way no losing the pcm mid-write due to low battery voltage

offboard and power

simply connect your pcm, don't forget to tighen the screw

then all i have to do is connect my dhp interface

turn on power, i used 12 low at first b/c i didnt wanna fry the pcm, but couldnt connect so i tried 12 high and no more problems, not in the pic but there is a switch for ignition power built into the harness

mid-write, battery voltage is showing ~14v

and success! all done in about a minute
BillBoost recommends using an old computer power supply or 12V power supply from Radio Shack for overamperage protection.

if anyone is interested in parts for making one i can get them pretty cheap, or i could get the parts, fab it up, test, and ship it to you
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