How to tell if your s14 is obd I or II??

[UncleBen]

I know the obvious thing is if its a '96 or up its OBD-II. But, '95s got OBD-II for half a year or something. I heard if the computer port thing is on the passenger side, its OBD-II. This is where I get confused....My car has a production date of 1994, yet the port is on the passenger side. Do I have OBD-II in such an early model '95?

[man2199]

If you have two Oxygen sensors your car is OBD II.

[D Money]

is the second O2 sensor next to the first one or is it under the car

[NISTECH]

one o2 on either end of the pre-cat determines if the car is obdII. not nessesarily near the cat but fairly close in the pipe. the primary difference between obdI and obdII is the second one has devices to moniter emissions equipment operation. like EVAP which was never monitered prior, cat efficency, and egr flow.

[proimport17]

I also believe on obd1 that the o2 sensor is a one wire and obd2 it is a 4 wire

[Structure240sx]

odbII should have all the extra vaccuum/emissions crap on the intake mani too. my car was made 4/94 obdI

[Dano]

I also believe on obd1 that the o2 sensor is a one wire and obd2 it is a 4 wire

hmmm, can we get conformation on this?

-Dan

[NISTECH]

most OBD II o2 sensors are 4 wire. some could be 3 wire. this is due to the heater in them.

[Dano]

so the one wire o2 sensors are OBDI?

-Dan

[NISTECH]

yes

[D Money]

i guess mine is obd1, but does it really matter?

[NISTECH]

for mods mainly it is important not just for emissions laws but check engine light related stuff. OBDI stuff did not genrally moniter if certain emissions components were actually doing what they were suppose to just weather or not it was turning on or off. OBDII has devices to "watch" the operation of the component during operation and if it does not see significant changes during its on or off time it will trigger a code. Couple of examples would be 1 the pre cat now has an o2 in front of it and an o2 after it the one after it is not used to control fuel but to compare the readings coming out of the cat to whats going in. if the 2 readings fall within 75% of each other a p0420/p0430 code is set. if you where to alter the exhuast ,ie. header,down pipe, you could trigger your CEL. Or another one would be altering or removing EVAP system components, The EVAP system now has 3 additional components to test and moniter its operation. Vent contol solonoid valve, evap system pressure sensor, fuel temp sensor, there are a handful of codes that could be triggered if you tampered the system. So to answer your question,yes it really does matter what system you are messing with. The ECM will try to adapt to a loss or malfunction of these items which may include fuel ratio changes, lack of horse power in extreme cases like cyl miss fire conditions where the ecm detects a miss from the crank angle sensor. miss fire detection is also a requiremnet of OBDII.

OBDI moniters are much more limited then that of OBDII. ITs montiers only require minimal info for example does the o2 register above and below a half volt when the car is warm. no specifics are watched just as long as it sees one of each. the evap system has no sensor to see if it actually working and your cat could be a tube and the ecm would be clueless.