FetusSoup

New to this entire scene including Honda itself, bought my first car recently, 1990 CRX HF, previous owner swapped in a D16Z6 (non-vtec). I read up on the engine and it says it's meant for OBD1, but my CRX has an OBD0 ECU (PR3 to be exact). I kept reading mixed results on the subject of D16Z6s working with OBD0 ECUs, some say it won't work, some say it does. Then the ones who say it won't work with the OBD0 PR3, but there is an OBD1 PR3 as well that should work with. I'd like to get a final answer.

The ECU itself, I'm not even sure if it's managing my engine properly, since it's telling me my O2 sensor is malfunctioning. But I don't have any spare sensors to try and test it either. So whether or not it's the OBD0 harness/ECU is up in the air for right now.

I want to upgrade to OBD1 regardless though, since it's what my engine was made for, and wanted to know if pulling the harness out of some other OBD1 car would work or if it's model specific wiring? Would any OBD1 ECU work as well or should I start hunting down a P28? How do I check the distributor to make sure it's not an OBD0 model swapped on?

Thanks.

//I meant to post this in the Hybrid board, oops! If possible could a mod move this?

jlicrx

the D16Z6 is a VTEC engine

the ECU is probably an OBD0 PR3 - the OBD1 PR3 will carry part no. 37820-PR3 - J## - if the letter is not J, it is OBD0 - it will run with the PR3, just not as good as it should - the PR3 will be looking for two O2 sensors and if you only have one, that would be why the code for O2

the OBD1 distributor will not work with the OBD0 ECU - the OBD0 MPFI distributors will not bolt right onto the Z6 head with all 3 bolts - the distributor has a number stamped into the side of one of the attaching arms - the OBD1 D16Z6 distributor is a TD42U - the OBD0 MPFI distributors are TD02U and TD18U

to switch it to OBD1, you use the engine harness that is on it - you need an OBD0 to OBD1 ECU jumper harness, P28 ECU, TD42U distributor and an OBD0 to OBD1 distributor jumper (or you can swap and repin connectors on the harness)

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ZCspeed Racing

GlassHeadlights

Excactly.

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FetusSoup

Alright, I see. I assumed my engine wasn't VTEC because the cover didn't say it was, but found out the cover on mine was replaced with a stock SI one to make it less suspicious.

The ECU is indeed an OBD0 PR3. And the distributor is labeled TD18U, so it's also OBD0 like you said.
When/If I upgrade to OBD1, with a P28 (or any other OBD1 ECU that might work with it, would all work the same or does it have to be P28 exactly?) will it still be looking for two O2 sensors? Will I have to tap the midpipe and jam in a second sensor still?

I might not be understanding you completely, since I'm still learning here. Do I absolutely need the OBD0-1 ECU jumper harness, and OBD0-1 distributor jumper?
Could I not take the entire harness from a car that is native to the D16Z6 (From a Del Sol or Civic) or possibly any Honda with an OBD1 harness? and trade it for my CRX's harness? Or is that what you meant by using the engine harness that is on it?

jlicrx

a stock Si valve cover won't work on a D16Z6 head - the VTEC heads have the spark plugs on the exhaust side and the stock Si head has them on the intake side - if the spark plugs are on the intake side, it doesn't have a VTEC head on it - if it has the PM3 Si head on the Z6 block, it is going to have a pretty low compression ratio - around 8.5:1

the P28 is the only D-series OBD1 VTEC ECU and would be the right one to use - other OBD1 VTEC ECUs would work but not very well - the P28 will be looking for one 4-wire heated O2 sensor

engine harnesses are not interchangeable between different models - you need to use the engine harness for the model of car you have and make any necessary wiring changes to it - the chassis harness ECU connectors for the OBD0 ECU are different from the connectors for the OBD1 ECU - this is why you need the jumper - you need to plug one side of the jumper into the OBD0 chassis harness and the other side into the OBD1 ECU - maybe the jumper should be called an adapter - same with the distributor - the connectors are not the same on OBD0 and OBD1 - you can swap the OBD1 engine harness distributor connector onto the OBD0 harness and not use a jumper

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ZCspeed Racing