PCM / OBD1&2 questions

[dnalbach]

I'm new to computer tuning and still trying to understand it better. Can somebody check me and correct any misunderstandings I might have?

OBD1 - Fixed PCM. 19XX? to 1993. You can replace the chips, but you can't reprogram them?

OBD1.5 - Fixed PCM with Flash Memory. Only in 94/95 years. You can swap out chips or reprogram them through the OBD1 port with a special cable, software, and laptop. Each reprogram requires a reboot, and this cannot be done "on the fly".

OBD2 - Real-time reprogrammable PCM. 96+. You can connect a laptop with a special cable up to the OBD2 port and modify PCM settings on the fly, even while driving.

[sil]

you can replace the obd1 27c256 uv erasable eproms with new eeproms such as 29c256 or the sf512 chips
just need an adaptor that will have a socket for the 29c256 or sf512, and allows the prom to plug in and bypass the 27c256 on the prom

not familliar with obd 1.5 or 2

you can even emulate in realtime with products such as the "ostrich"
basicly you plug the ostrich cable into where the eeprom goes, and then hook it to your computer and run compatible software such C.A.T.S or tunerpro rt ect..


heres what the adaptor looks like

[dnalbach]

What do you plug this adapter into? Is there a plug on the PCM for it? Once the original eeprom is bypassed, is the new eeprom reprogrammable? If so, how?

For the Ostrich, would the laptop emulation be able to make changes in real time, or is the PCM just reading the eeprom once at engine start? Or does it read from it continuously?

[sil]

the adapter plugs into where the prom goes inside the ecm, then the prom goes onto that

yup you can manually remove the chip for reprograming, using for example a pocket programer or a willem programer

http://www.mcumall.com/comersus/store/comersus_dynamicIndex.asp

ostrich will emulate "tune" in real time, you can make a single change and your pcm will see the change

[ryan.hess]

OBDI you can tune on the fly, as Sil mentioned.

OBDII as I understand it, you have to pull over and shut off the engine before you upload the new programming.

OBDI.5 is one of those weird things nobody uses or wants to talk about

[Rhedalert]

OBDI.5 is one of those weird things nobody uses or wants to talk about

agreed

[dnalbach]

I have a '95 Olds with OBD1.5 so I'm confused as to whether I should try to go forward to OBD2 or backward to OBD1 and which would be better?

[bszopi]

Forward to OBD2 will give you more options IMO and its relatively easier to tune since you don't have to pull the chip out, burn it, put it back it, etc... Just hook up the cable and make the changes to the program.

[napatiger]

I have a 96 LQ1 ECU and harness off ebay. The harness is pretty cut up, do I need to replace all the wires or can I just change the ECU and a few wires?

[blackbombshell95]

I have a obd 1 from a 93 dohc with a full wiring harness plus all the parts to convert your car to obd 1.0

[Azrael]

From what I understand the OBD1.5 can be reprogrammed but only from a GM TechII station. And that GM technicians are heavily regulated on what changes they can make. I could be wrong about this though.