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Replacing melted engine wiring harness

smkdjnt

NAXJA Forum User
Location
San Diego, CA
All,

I am looking for some help on this issue. I have a 2000 xj with a melted wiring harness for the engine (sensors, injectors) part of the loom. I have replaced it with the same year manual trans harness (new) and it runs and drives. I have had to add the sensor wire from the TPS to the TCM for proper shifting, but that's all the difference I could find. The issue is at key on my ASD relay clicks and cycles power for everything including fuel pump, sensors and injectors and efan. Once running, no issues. While key is in on position, my gauges also don't work UNTIL it is running, then everything works. I have no CEL light except at key on, but I am not able to connect until it is running. I have verified all grounds, unplugged all sensors and TCM and the only thing I can determine is when the harness is connected to the other loom at the passengers side firewall and on the PCM, it does this. I have swapped PCM with a known good spare and both will do this. Any ideas are appreciated, I am at a loss on this one, thnx for reading.

Again I have disconnected everything from each harness so only the two harnesses, and at the firewall are connected and at the pcm, and it does this still with a new stinkin ASD relay..:smsoap:
 
All, I have done some further troubleshooting on this issue and could use some thoughts.

With the ASD relay removed and key ON, I eventually get NO BUS on the odometer and a CEL with the following codes.

P0122 (TPS A circuit low input)
P1694 Powertrain TACOMETER circuit high voltage

With the ASD relay in place or removed there is no change with the guages either.

I did a pinout of the relay and here is what I have

Pin 2 (Fused Circuit) 11.8 volts at key on, open loop
Pin 4 (Fused Circuit) 11.4 volts at key on, open loop
Pin 5 (Not Used)
Pin 6 (ASD Relay Control Circuit to PCM) good resistance to C3 at PCM (0.0). Pin 6 to ground is 3.14ohms
Pin 8 (ASD Relay Output, Green/Orange (+) supply ~ injectors, coil etc) 30.9ohms with key on, 15volts

----[]2---
[]6----4[]
----[]5---
----[]8---

ASD Relay installed, NO BUS goes away and mileage returns without cycling key.

If anyone can tell me if the ASD is right where it should be, id appreciate it. Thanks.
 
So issue was resolved. I had the sender ground wire for my downstream O2 sensor shorted with the (+) circuit due to the connector rubbing along the drive line. Not enough to blow fuse #21 in the PDC, but enough to trip the ASD and screw with the ground for the PCM. Resistance on the circuit was around 25-30ohms. Once corrected I also swapped out the IAC and now it starts, no issues.
 
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