96 S10 LSx Swap, OBD2 Data Issue

[FirstGensForever]

Truck is a 96 S10 Extended cab, originally a 4.3 Vin X 5 speed, Z85 suspension, non ZQ8 with factory 8.5 rear axle. We have swapped in a 408LSx T56 using a Current Performance harness and have removed the ABS entirely so the stock ECM is no longer around.

The truck is running and driving, no CEL, i have power and ground at the OBD2 port and i have continuity between pin 59 on the ECM and pin 2 on the OBD2 connector. With the harness connector installed into the ECM, i also have continuity to pins 4 & 5 on the OBD2 port which are chassis and system grounds respectively, and also pin 8 which is CCM diagnostic. With the ECM plug removed from the ECM i only have continuity to between pin 59 and pin 2.

My question is, would this be considered normal. Ive gone as far as cutting the harness wire at pin 59 and pin 2 and connecting a jumper wire between the two completely bypassing the wiring harness altogether and i am still not able to get serial data on pin 2.

I removed the dash to replace the heater core, and in the process of putting everything back together there is a junction block on the passenger side of the dash behind the glove box, one of the wires got pinched between it and the metal mounting bracket, when i first hooked up the battery to try and start the truck one of the fusible links on the drivers fender junction block blew. I wasn't sure what this link controlled since they aren't labeled, but the truck cranked over but wouldn't start. I had no power to the fuel pump or ECM, i applied power to the fuel pump bypass plug and it powered up just fine but still wouldn't start. After a few days of retracing my steps i found the pinched wire, fixed it, replaced the fusible link and the truck fired right up. But its not running to great since the tune isn't 100%.

As far as can tell the pinched wire didn't cause any other problems, but im wondering if it somehow is the cause of us now not being able to link to the ECM thru the OBD2 port. With the ECM out of the truck and on the bench, Nelson can connect to it just fine.

If i cant come up with some options to check, or somebody that has maybe had this problem before im going to have to remove the harness and send it back to Current Performance for them to check it out. Something somewhere is blocking the data signal is what i think, cause if i have continuity on the circuit, i should have data connection as well.

Thoughts, Comments?

Thanks for any and all help.

[FirstGensForever]

Ok, got an update. I went to the pick a part and got some pcm harness ends to make a bench top type harness to see if i can connect to the pcm out of the truck. With ground wires hooked to pins 1 & 40 on both the red and blue connectors, battery positive connected to pins 20 & 57 and also power into the OBD 2 connector and pin 19 ignition power and a wire going from pin 58 to pin 2 on the obd 2 plug my code reader/scanner connects just fine in about 1 or 2 secs with pass no codes present.

I then checked the pcm plugs and pins 1 and 40 on both the red and blue connectors have continuity to ground, pins 20 and 57 have 12V all the time and pin 19 has 12V with the key on.

I put the pcm back in the truck and plug into the under dash obd 2 plug and it wont connect. If everything has power and ground like its supposed to be then it should connect. I'm ready to give up on this but not just yet.

The only thing i came across is that with the key off pin 19 has continuity to ground, and with it on it shows 12V. With the key off and the neg test lead on the alt. stud and the positive test lead on pin 19 is shows -12V, could this mean that pin 19 is shorted to ground, but is somehow still able to send 12V to the pcm with the key on but is causing the issue im having with not being able to link to the the pcm thru the obd2 plug??

Any ideas?

[RedHeartbeat]

I'd break out the multimeter and circuit test each lead, PCM end to connection end. I prefer to send a load through the wire for testing, like have a dome light circuit created using a battery and leads and then start testing for current flow. Sometimes you can have a complete circuit when tested with a multimeter but it will not carry any voltage due to all but one or two strands in a wire broken or shorted.