View Full Version : 95 240sx OBDI or OBDII

02-08-2005, 08:15 PM
How do you tell?

AEM has the EMS listed as 30-1610 and 30-1611 (OBDI and OBDII respectivly) They list the 95 as coming both ways. What they dont tell you is how to tell what you have.

Is there a definative way to determine if a 95 is OBDI or OBDII?

02-08-2005, 08:39 PM
I'm 99 percent sure that 95s were OBD1. Import cars weren't OBD2 until 96.

02-08-2005, 09:41 PM
And I think all 95's are really OBDII, I have one the was built 4/94 and it's OBDII. So I would assume with mine being that early off the assembly line for 95 that all of the 95's are OBDII, However your answer on how to check is really easy. Go to Autozone and tell them you want to get a free comptuer diag done and then tell them the plug should be on the passenger side under the left side of the glove box (the plug is gray). If they tell you they dont' see a plug look for yourself it's easy as hell to see and if you don't see it then just tell them the guy who told you it was there must of been mistaken. And that will tell you that your not OBDII the reason I say take it there is that way if you do have a plug they can plug into it and if their computer pulls info off yours then your deffently good to go that your OBDII.. Oh yeah and I guess you could save some hastle and look for the plug yourself first don't know why I said go there first....

02-08-2005, 10:14 PM
Every S14 I have ever seen or worked on has BOTH OBD diag ports.

I have tried to link my Snap On scan tool to my car and get nothing from the OBDII port.

My car also has none of the extra sensors, vac lines, second wire harness, etc in the engine bay that all the 96 and up cars I have worked on have.

I seem to remember the primary O2 sensor on the 96 and up cars having a multi wire 02 sensor and mine has a single wire.

02-08-2005, 10:53 PM
I have talked to AEM and they list both part numbers for the 95 depending on if you have OBDI or OBDII. I was told that the EMS is set up differently for each. Is there an actual difference in the factory ECUs in the 95 model? Anybody got a pin out of a 95 ECU and a 96 or newer ECU?

Basically everytime I ask AEM how to figure out the difference, they tell me the OBDII has more wires... When I ask more wires then what, they tell me more then the OBDI. But if I dont know how many wires each have, HTF am I supposed to figure this out?

02-08-2005, 11:14 PM
As far as I know all 95s are OBDI. However, all 95s were being guinepigged for OBDII. Hence all 95s having two O2 sensors even though the second O2 sensor on my car only checks to make sure that the cat is working by checking for a different voltage from the primary O2. I also have my 95 FSM sitting right here and there is nothing at all on OBDII. According to my FSM there are a total of 88 wires going to the ECU plug (F1), 1 through 70 and then 101 through 118. Lastly, EC-7 of the FSM shows the entire layout of the emission control overall system and there is nothing like you would see on an OBDII equipped car.

02-08-2005, 11:18 PM
FWIW, I have used a '97-98 ECU, '95 ECU (stock and JWT N/A tune), and '96 ECU (stock and JWT turbo) in my '96...no weird issues that I can speak of...no way to tell the difference.

The difference in '97-98 vs '95-96 are the A/C wiring IIRC, JWT details this on their website.

I would wager the "extra wires" are the O2 heater, and maybe an EVAP solenoid. Nothing important, really...

Let us know what you find out - Brian

02-09-2005, 12:33 AM
Is there a definative way to determine if a 95 is OBDI or OBDII?

Ivan, look at the ECU part numbers. Even though originally there were 9 different ECU part numbers for the '95, they've all been superceded by two part numbers. The cutoff date between the part numbers is 7/95. Later model '95s share the same ECU part number as early model '96s... and ALL '96s are OBD-II.

Based on this, you can conclude that up to 7/95 is OBD-I, and 7/95 and after is OBD-II. What if your car was manufactured in 7/95? Well then look at the ECU itself.... A18-E87 G93 is OBD-I and A18-E27 G46 is OBD-II.

Hope that helps.

02-09-2005, 12:53 AM
I can tell you that I have tried to use the MAC Mentor on my 95 240 and it requires a special harness that requires me to connect to the Nissan consult port and OBD connector. The OBD connector does not work without it. It is my understanding that OBDII is a government standard requiring all cars have a universal port to connect to the computer on every car. Therefore because the OBD connector does not operate our scanners on a 95 it is not OBDII. I have a snap on scanner and the New Mac Mentor and have tried both just for testing purposes. As far as being a mechanic shop the 95 is not considered OBDII vehicle because all OBDII vehicles only require the OBD connector to operate.


02-09-2005, 07:41 AM
If my car isn't OBDII then why can I plug and OBDII reader into the plug under the passenger side and reset the comptuer to turn off check engine light. Why is it when the water temp sensor was unplugged it told me? OH and even if the car is "kinda" like some of you are trying to say, if a computer for OBDII plugs plugs in and you can get readings from your car it is OBDII for all intensive purpose.

02-09-2005, 08:50 AM
for all intensive purpose

I think you meant "for all intents and purposes".

Carry on.


02-09-2005, 10:28 AM
This is how I found out for sure...Take the VIN to the dealer and ask.

02-09-2005, 03:02 PM
some 95's are in fact, obd II