XJ Engine Harness Questions

[jsawduste]

Hi guys, crawled up from the YJ basement to ask a couple XJ questions. A model that frankly I have little knowledge of when it comes to specifics.

My stroker equipped YJ is running OBD1 SBEC engine management.

Wish to convert to OBD2 in order to take advantage of the folks whom have the ability to actually reflash the ECM programming. These folks can also do data logging via the diagnostic port under the dash. This will allow for changes in fuel trims, spark mapping etc.

Looking at getting an XJ engine harness(es)........The ECM located up by the front fender gives me a lot of choices for packaging without cutting wires....... Whereas a TJ ECM located on the firewall kinda limits things a bit. I am not worried about the ECM controlled gauges and such. Just the actual engine and associated harnesses with the data port.

Few questions

Pretty sure OBD2 started in 96, is that true ?

Would like to avoid the coil packs. What year did the coil packs get introduced ?

Is there separate harness(es) for the alternator, fuel pump etc ?

What is involved with removing the wiring to the dash data port ? This is important as all the data logging and some reprogramming will be via the DP.

I am not afraid of doing some rewiring and even making new harnesses as needed (I`ve completely rewired my YJ) but getting a start with the correct components helps.

I see folks parting out XJ`s on CL and also the local 4x4 forums but especially when it comes to coil packs I am not sure what years to look for. In addition it might end up that I have to remove the harness myself. No biggie but having a little knowledge especially when it comes to the DP would be a plus.

Thanks !!

[akadeutsch]

OBDII was in fact a mandate in 1996...in the US. Coil packs came on the scene in 1999 along with the introduction of the 0331 head and new high flow intake. I have yet to see a mod to rid us of that coil over ignition rail (packs) while maintaining the desirable 0331 head...But my coil pack has yet to fail, so who's complaining. It sounds like you want to stick to the 0630 head...at the cost of significant flow and very dynamic runner differences. Why do you loath the cool new secondary rail (packs) so much? If your conversion is a success you should be fine running the coil packs I would think. I could be

[SilverXJ]

I have yet to see a mod to rid us of that coil over ignition rail (packs) while maintaining the desirable 0331 head..

You haven't looked hard enough then.

[jsawduste]

OBDII was in fact a mandate in 1996...in the US. Coil packs came on the scene in 1999 along with the introduction of the 0331 head and new high flow intake. I have yet to see a mod to rid us of that coil over ignition rail (packs) while maintaining the desirable 0331 head...But my coil pack has yet to fail, so who's complaining. It sounds like you want to stick to the 0630 head...at the cost of significant flow and very dynamic runner differences. Why do you loath the cool new secondary rail (packs) so much? If your conversion is a success you should be fine running the coil packs I would think. I could be :bs:

:cheers:

AK, read some more on this forum. Pay close attention to the signatures. Ask a friend hint, Silver.

To answer the other side of your question. I am using a 96 XJ harness which turns out to be a mutt of sorts. The connectors for the sensors are OBD1 while the wiring for the ECM is OBD2.

If I had to do it over again I`d of simply taken the OBD1 harness and re-terminate the ECM side to OBD2. Ryan mentioned a customer whom had it done and after studying both architectures I`ve found they are the same. Then add the SCI protocol which for 96 only did not need the canbus/cluster combo to communicate with the diagnostic port. The 96 ECM for some reason is not as friendly as latter models to reprogramming so a later vintage ECM would be in order.

Having said that, the quality of the 96 harness is much higher then the OBD1 95 down. Better quality and heavier gauge wires in some areas. The routing and a host of other small attention to detail items makes for an overall better thought out harness. Based on those facts the time and effort to rework the XJ harness makes it worthwhile but again it could be done ether way.

I will be keeping the 7120 head for now but am considering upgrading the TB to a larger diameter.