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Thread: OBD2 -> OBD1 stepdown harness diagram

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Posts: 21-30 of 87
2010-05-24 22:06:52
#21
Originally Posted by sr20jet
The last Sentra I had was sr20 swapped in. Previous owner hacked the harness, leaving me with a air intake temp sensor code (missing from harness), and rear o2 code. With the downstep harness, I was able to use a OBD1 ecu, which don't have AIT and rear o2 codes. This took care of the issues I had passing inspection.

The rear o2 issue I had was due to the car being a 1.6, the rear o2 sensor is on the engine harness as opposed to 2.0 Sentra which is inside under driver seat (My interior harness was the GA harness).


I can't speak for the rest of the States, but in the places I've talked to in GA and tried to pass it's all failed because the OBDI ecu just will not talk in ODBII talk. The CEL will not flash when asked too, it will not report all the asked for data, and so forth. Hell, I make adapter harnesses and I know for a fact that the 5 wires that go from the OBDII ECU to the OBD connection cannot be made because the OBDI ecu does not have those outputs.

But if you've got a place that's passing you then that's freakin rockstar. I wish I could find a place down here that I could bribe too pass me so I could register my car in the county I live in.

Originally Posted by Pretty
Does this step down harness cut the CEL and still allow the OBDII to pass with the plug in test?


A properly made harness will not throw a CEL, and additionally you will get a CEL when you are suppose too (i.e.: when something goes wrong with the car). To add, a correctly made harness should be fully interactive with the Concult port. HOWEVER, just because you have no CEL does not mean you will pass emissions. OBDII inspections require the ECU to talk to the test computer. OBDI ecus do not speak this lingo, nor do they have the ability too.
2010-05-24 23:00:44
#22
EDIT:

Oh damn didn't realize this had a second page
2010-05-25 02:18:15
#23
Originally Posted by sr20jet
This took care of the issues I had passing inspection.


Emission is the only thing we have to pass. If we had to deal with inspection, a lot of cars in CT would not see the road
2010-05-25 13:10:19
#24
Originally Posted by Lu6i4
Emission is the only thing we have to pass. If we had to deal with inspection, a lot of cars in CT would not see the road


Well in PA & NJ, it's an auto fail for emissions related codes, like what I had with the rear o2. Without the stepdown harness, I wouldn't even pass emissions.
2010-06-15 21:40:47
#25
Okay I picked one of these harnesses up, I need to convert the distibuter over do i not ? along with the coil and igniter ? or will the obd2 dizzy work with a obd1 ecu ? I have yet to find out the answer to this question on three forums
2010-06-15 21:54:21
#26
I'm using an OBDII dizzy with an OBD1 ECU.
2010-06-16 03:48:04
#27
Hey zer099 I will need one of these obd2-0bd1 stepdown harness later this year.

I was wondering if you can do rewiring for the gauge clusters? My 92 1.6 came with a cable gauge cluster with out a tach. I have this spare cable gauge cluster with tach, but it needs rewiring so it can work properly. Can you do this type of job?

- Alex
2010-06-16 09:50:17
#28
I can look into it if you like.


EDIT: Looking at the FSM, it appears that Nissan (in their infinite wiring wisdom) was nice enough to use two almost completely different wiring layouts for the Tach model and the non-Tach models. But, it can be done (of course, almost anything can be done). And adding the Tach signal is as easy as just making sure the signal wire is there from the ECU.
2010-09-29 15:19:14
#29
What about a P11 (00+) to OBDI stepdown?
2010-10-26 04:19:52
#30
can sum1 email me the diagram
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