ecu questions
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0.5 BAR
Joined: Sep 2003
Posts: 64
ecu questions
I searched but can't find an answer that is this basic. I know party of the wiring harness connects to the ecu. Where does the other part connect to? Why do people have to modify wiring harnesses like on a h22 in a prelude, can't you just use the prelude wiring harness and ecu or the original civic wiring harness and ecu? Or like putting a b16a2 in a 92-95 ex couldn't you just use the original p28 or the jdm ecu? Another question I have is what is the difference between obd0, obd1, and obd2? Why cant you put an obd0 in an obd1 car or and obd2 in a obd1 etc without modifications? I'm just confused on what happens to the ecu in swaps.
3.0 BAR
Joined: Feb 2003
Posts: 9,089
Re:ecu questions
ok when going from obd0-obd1-obd2 you have too add sensors meaning wires, usualy 2 per sensor. The harness itself is actually 2 pieces.. mind you there are alot more wires and connectors then this diagram but here goes.
ENGINE (connectors) -----[][]-------[]ECU
this way you can just disconnect the harness where you see [][] (at both wheel well areas) and remove the entire engine with the engine harness on and the ecu harness still in the car.
the reason you need to change some wiring is for a few reasons....
1. Sensor location - you might need to extend some wires to reach the same sensor on the prelude motor, but at a different position.
2. Connectors - some connectors are just different, similar sensor, just different connectors.
3. obd version and features - some engines have more features then others, like vtec motors. If you want to put a vtec motor in a non vtec stock car you have to add the proper wires to activate or use those features.
4. ECU wire locations - some ecu's have different locations to plug which wires into what. For example.. an o2 wire may be in pin a11 for your stock 90 civic si. if you want to swap to a say del sol vtec motor you might have to change that wire to pin a12.
Hope i shed some light on the subject for you.
ENGINE (connectors) -----[][]-------[]ECU
this way you can just disconnect the harness where you see [][] (at both wheel well areas) and remove the entire engine with the engine harness on and the ecu harness still in the car.
the reason you need to change some wiring is for a few reasons....
1. Sensor location - you might need to extend some wires to reach the same sensor on the prelude motor, but at a different position.
2. Connectors - some connectors are just different, similar sensor, just different connectors.
3. obd version and features - some engines have more features then others, like vtec motors. If you want to put a vtec motor in a non vtec stock car you have to add the proper wires to activate or use those features.
4. ECU wire locations - some ecu's have different locations to plug which wires into what. For example.. an o2 wire may be in pin a11 for your stock 90 civic si. if you want to swap to a say del sol vtec motor you might have to change that wire to pin a12.
Hope i shed some light on the subject for you.
1.0 BAR
Joined: May 2003
Posts: 362
Thread Starter
0.5 BAR
Joined: Sep 2003
Posts: 64
Re:ecu questions
Believe me I searched, but I can't find a basic ecu engine swap faq. I still don't understand where the other part of the wiring harness besides the part that the ecu connects to and why you can't use your original ecu.
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rsmith2786
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Jul 10, 2007 09:09 AM
