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OBDI Vs. OBDII compatability?

1K views 1 reply 2 participants last post by  bonesaw 
#1 ·
Does anybody know for sure if an OBDI ABA harness can be modified to run OBDII?

I am aware of the differences on the motor side, so lets leave those comments out.

The reason I am asking is I would like to avoid making another harness for my car and would rather modify the one I have in the car currently.

The car in question is an 87 Jetta coupe which uses the early CE1 fusebox similar to that found in the Cabriolet/Scirocco/Caddy. The motor in the car is an OBDI ABA from a 95 Jetta. I am upgrading to OBDII to utilize a recently acquired Neuspeed charger, chip, and injectors as well as switching to the integrated throttle body.

Last weekend I went and pulled an OBD harness to use and I currently have the OBDII ECU, Throttle body, MAF and pigtails/connectors for the O2 sensors.

Why not just switch out the harness?
The harness in the car has been gutted, spliced, lengthened, and re-routed which took quite some time to finish. I would rather not go through this entire process if it's not absolutely necessary.

Here's a shot of the harness before putting it in the car and soldering it back together:

Here's a shot of it in the car:

The O2 sensor and MAF got to the other side of the car, the ECU is in the center console and the coil is on the kick pannel above the fuse box.
The coiled up wire is the headlight harness.

Any info would be appreciated, I am going to start tearing into the new harness this weekend.
 
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