Here is the situation: I am currently working with a PCM guy (don't want to mention name) on a computer that will allow us OBD2 guys to pass emissions and get our cars taggged with majorly modified cars and/or aftermarket computer systems.

What I am working on is basically taking an OBD2 PCM from a stock car and using the memory from the computer and splicing into the data output wire in the under the dash ALDL connector. This can be used if you have switched to an OBD1 PCM or if you have FAST, Accel DFI, etc to make it read as though your car was free from trouble codes and is stock. As you all know the DMV inspections for OBD2 cars require the car to pass the PCM test in order to get tagged even if they run speaky clean through the sniffer.

The problem we have been having is transferring the car to another vehicle. We are losing power going from the car battery to an external portable battery even with the connections plugged in simultaneously (car battery and external battery). We are trying to stick with a battery that is less than 10 lbs for shipping reasons and for transportability reasons. Is there anyone that knows why the PCM is losing its power through the process of switching power sources? What about batteries?...does anyone have any recommendations?...we would like to have something that can power the memory part of the PCM for at least 2 weeks for shipping reasons. Does anyone know the specifics on what is needed powerwise for the OBD2 PCM to hold its memory of drive cycles? Any help on this project will be appreciated...I need to get my car tagged!!

Thanks
Matt

 

I really doubt that is going to work. Just splicing in the data connection into the ALDL will not do it. For one thing the PCM stores the VIN information. Don't the inspection guys check that?

Ok if you get by that problem, won't the inspection fail if there are DTC codes stored? And there will be DTC stored if you try power up the PCM in a car with nothing connected to it.

If your car is running a FAST system, and you install a OBD2 PCM into the car just so the smog people can scan it you have to remember that the PCM will be looking for all of its normal inputs and outputs. If those are not there its going to set all sorts of DTC codes. Here in Oregon the smog stations just scan the car, check for DTCs and the corrrect VIN in the PCM. If there are no current DTCs then you get a sticker and you can get your tags.

Heck if you want to keep the memory alive in that PCM, just get a 9v battery and connect it to the necessary points that are connected to BAT 12v. It is just like keeping the CMOS alive in your desktop PC. It would last for weeks.

 

Thanks for the reply! So I assume the best away around this would be to get an OBD2 PCM prgrammed for my car's vin number and put the proper resisters in the sensor areas of the PCM to keep from having DTC codes by making the PCM think it still has the wiring harness hooked to it with all of the sensors. Then switch it from the stock car with saved drive cycles to my car while having the PCM memory powered up to save the drive cycles then when the PCM is put in my car I power up the PCM with a 12 volt switch to the PCM to power up the PCM when the inspector plugs the car in. Would this work?

Secondly, If I were to buy a custom programmed OBD2 PCM for my car and had the EGR, AIR, CATS, and all emissions related equiptment deleted and was programmed for my combo would it pass the inspection test? If not , Why?

Thanks Again
Matt

 

This really should have been posted on the "Computer Diagnostics....." forum. Moving it there......

 

ttt....madwolf????? Anyone????
Later
Matt

 

Getting a VIN programmed in an OBDII isn't the part that's most complicated... it's turning off all DTC in a way that the sensors will still show reasonable values that's complicated.
I can turn off the DTCs in an OBDII through programming, but I'm not sure how that will work. If all they do is check for stored codes, it will, but if they check for live sensor data, you'll have to go the resistor way... which also might not work very well because sensors such as o2 sensors fluctuate very often and the values are quite a bit different. A resistor will keep the values steady at all times, or at least, very close to steady.