Quote:
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Originally Posted by unknownluder69
whats the difference in the two??
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from
www.frogenginecontrols.com i paste this.
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History and Technical information about OBD
OBD was first introduced to the North American market in 1992. The first version is commonly
referred to OBD1. This configuration lasted through the end of the 1995 model year. Fuel injection
became commonplace in Civics starting in 1988, though the Si versions of the CRX and Civic had
fuel injection as early as 1985, and was introduced in the Integra with the launch of the 1986
Acura line. Before 1992, there was little if nothing in the way of on board diagnostics in the ECU.
The 1988 to 1991 is commonly referred to as pre-OBD or OBD0 (the 0 meaning no OBD).
Starting in 1996, OBD made some big advancements and was now referred to as OBD2. It now
became apparent that emissions had to be cut, and maintained at reduced levels for extended
mileages or periods of time. The ECU now monitored the crankshaft speed to see if fluctuations
occurred that would point to lean mixtures or a failing ignition system. It also monitored the
efficiency of the catalytic converter via a second oxygen sensor mounted downstream of the cat.
This meant that those of us that wanted to run a test pipe to eliminate the restriction associated
with the catalytic converter were faced with check engine lights as the ECU would detect lost
efficiencies due to the lack of the cat, or O2 sensor failures from the removal of the sensor.
Several products hit the market that were intended to simulate an O2 sensor and fool the ECU
into thinking that the cat was still operating efficiently. Its a little known fact that the check engine
light for the 2nd O2 sensor, or for the missing cat will not lead to the ECU operating in "limp
home" mode. It just simply leaves a glowing light on the dash to annoy you. OBD2 also added a
pressure monitor in the gas tank to insure that the pressures were building normally inside the
tank to indicate a properly closed gas cap and normally functioning evaporative emissions control
system. In 1999/2000, the connections on OBD2 ECUs were moved around, making them
completely incompatible with the 1996-1998/1999 chassis and ECUs.
Though the ECUs from the JDM 1996 and up cars appear identical to their North American
counterparts, they are very much the same as the USDM OBD1 ECUs in their operation, lacking
the crank speed fluctuation and fuel tank pressure sensors, as well as the 2nd O2 sensor from
the USDM OBD2 cars. This makes them ideal for those wanting to run the JDM ECU that was
supplied with their 1996 and up JDM engine swap in their 1988-95 car. For those of you ambitious
enough to try and use the North American OBD2 ECU from your 1996 and up USDM swap, look
forward to lots of extra work incorporating the fuel tank pressure sensor, as well as the extra O2
sensor or one of the many O2 sensor simulators on the market.
One thing to keep in mind anytime you are swapping an engine from a different generation of
engine management into your car is to stay with your existing engine wiring harness. It is always
100 times easier to make the necessary mods to the engine harness that came with your chassis,
then it is to make mods to the chassis harness to match the engine harness.
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that being said - a lot of people (who mod) prefer to run obd1, so they buy a jumper harness, then they can get rid of the second 02 sensor, and some other hassles that obd2 enforces.
The problem is when these people go to get emissions checked - if it's a place (ie: cali) where they use more than just a sniffer - and they try to
"hook up" to your obd2 with a scanner (because these guys are by the book remember - they'll look up the year of your car - and then say "oh this one is obd2" and out comes the scanner) - and if your running some harness to an obd1 - it's not going to scan anything - and you will fail emissions. I assume that's why the poster of this topic wants to keep his car legal - so he doesn't have to go thru these troubles later down the road. Unfortunatley for him (and honda at the time i assume) the 96 prelude happened right on the boundary of honda's model change, so he's left looking for a somewhat rare ecu, especially if it's vtec, because i imagine 96 vtec's are still in high demand - plus you have the accord community dropping h22a's and wanting to stay obd2 as well.
hope that helps...