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98 Civic LX
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175 Posts
Discussion Starter #1
Being Honda I assume when they went from OBDIIA to OBDIIB they only changed the engine harness. Can anyone confirm this? Is it possible to repin a OBDIIA to a OBDIIB ECU with only changing the engine harness?

More specific, after the repin and the use of a OBDIIB ECU and engine into what was a OBDIIA car would it run the same? (gauges, OBDII connector, ignition, ect.)

Here is the goal so you can see what Im trying to do.
Car: 98 Civic LX (OBDIIA)
Engine: 99 CRV B20 (OBDIIB)
Ecu: 99 CRV B20
Engine Harness: B20

If im not clear ill try to say it another way...
 

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the artist formerly known as drexelstudent11
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3,983 Posts
they changed some of the engine-end harness plugs too, but afaik the level of required sensors and stuff didn't change. since it's a 96-00, can't you just swap the whole harness over from the CRV, or are they a multipiece like a teg/delsol/5th gen harness?
 

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the artist formerly known as drexelstudent11
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3,983 Posts
Just use a obd2a to obd2b jumper harness at the ecu.

but the switch included more emission stuff (egr evap etc... ) and switch the dizzy. They removed a wire or 2 from it.
I don't think they did for B series stuff though
 

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98 Civic LX
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175 Posts
Discussion Starter #5
i have both cars in my garrage. I dident want to remove the dash from both to switch the entire harnesses. If i have to i will just want to know if there is a way without doing the cabin harness too
 

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Not only are the ecu plugs different but the green plug and the gray shock tower plug are different plugs. There is all a difference in sensor plugs from a d-series motor to a b-series motor.

So in order to use the obd2b engine harness in an obd2a chassis you will need to swap the cabin harness. Now the question is how different are the cabin harnesses. This I'm not sure about.
 

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Do you still have the stock harness from the Civic? If so just use it and get a OBD2a to OBD2b adapter, less headache and risk or screwing it up
 

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98 Civic LX
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175 Posts
Discussion Starter #8
damn, alright. Thanks guys. I guess ill have to do the leg work.

Ill look for that jumper though. ill just have to add a knock sensor wire i think
 

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98 Civic LX
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175 Posts
Discussion Starter #9
New thought.

Can I just repin the civic cabin side connectors (Green block, gray and blue) to the CRV engine harness?

I guess the question becomes is the dash gauges wired the same....
 

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Now the question is how different are the cabin harnesses.
IIRC, the cabin/floor harness should only add the pressure sensor for the tank. But there might be one other evap system sensor back there as well. Its been a while since I have been under the really early OBD2b cars.

Side note: requirements for sensors for OBD2A/B are the same for d or b or h or f or j (meaning obd2b d has same sensors as obd2b b/h/j/f or obd2a d has same sensors as obd2a b/h/f/j). Its an across the board system design. Like the tank needed a pressure sensor, two way valve, and the location of the OBD diag port (including how its wired).. Personally, I would use a OBD2A system through out.
 

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IIRC, the cabin/floor harness should only add the pressure sensor for the tank. But there might be one other evap system sensor back there as well. Its been a while since I have been under the really early OBD2b cars.

Side note: requirements for sensors for OBD2A/B are the same for d or b or h or f or j (meaning obd2b d has same sensors as obd2b b/h/j/f or obd2a d has same sensors as obd2a b/h/f/j). Its an across the board system design. Like the tank needed a pressure sensor, two way valve, and the location of the OBD diag port (including how its wired).. Personally, I would use a OBD2A system through out.
Remember that same sensor are different from d-series to b-series motors. The crank sensor on a d-series uses a 3 wire were the b-series uses a 2 wire. The pin outs are all so difierent between obd2a and obd2b.all so the distributor plug is different on some d-series,some use an 8 position plug and some use a 10 position plug. The obd2a harness has all 3 ecu plugs I it the obd2b only has 2 ecu plugs on it.
 

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15 WRX STi
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76 Posts
^^
Listen to this man

If anyone on here knows, its him.
X2 one of few "guru's" here.
Onatop is another member to look for when it comes to wiring. I'll ask my buddie this weekend about your question and get back to you.
 

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98 Civic LX
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175 Posts
Discussion Starter #14
Thanks for the info, I am aware of the differences in the connectors and sensors and that. I went knee deep in my swap and had to revert everything after i found this out.

The question is: can i repin the OBDIIA cabin harness of my civic to accept the OBDIIB engine harness of the CRV. I have all the ecu pinouts labeled between the two. I just want to know before i unpin two harnesses that when i (correctly) repin my harness the gauge cluster and the rest of the dash will still work.
 
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