Injector Circuit Malfunction - P0206 / P0432

[Wingback73]

Hi folks,

I have a 2004 4.0L TJ 5-speed Rubicon, 135K, that has recently started acting up, and could use some help in 2 areas:
1. Does anyone know where to source pins for the Injector Circuit both @ the injector itself and at the PCM?
2. Does anyone have any different troubleshooting ideas?

Longer Story:
I've had this 2004 TJ for a couple years. It runs great, and while I've done a bunch of mechanical work, I've done little to the engine since it is is strong condition. It has a bit of lifter tick, but nothing substantial.

About a year ago I got a random P0306 misfire code that was coming and going, often times accompanied by P0206. Since the vehicle had about 130K I didn't know when they were done I replaced the plugs and the ignition coil. Obviously that didn't solve the problem or I wouldn't be here, although it did go away for quite a while.

More recently, I got a P0432 Main Catalyst efficiency. I'm not too worried about this since I'm not required to pass emissions anymore, but throwing it in for completeness.

in addition, I'm not also getting P0206 again. No P0306 misfire, just the ignition circuit malfunction. My understanding, which I'm happy to be corrected on, is that this code means the PCM is requesting the injector to open, but is reading a different condition than expected. So unlike a P0306, this isn't about air/fuel, but rather about electronics.

Accordingly, I swapped injectors 5 and 6. This made no difference: P0206 returned.

I'm now, I think, left with either:
a) my injector circuit is bad, or
b) my PCM is bad.

It seems more likely to be a) since the issue is highly intermittent, and b) seems to correlate to hitting a big bump (but again, since codes aren't instantaneous, it is hard to say).

I would like, at this point, to replace the circuit from Injector 6 to PCM w/ a pair of direct wires (no splices, connections, etc) replacing the pins in the injector and PCM harness. If the problem goes away it is wiring; if it doesn't, it is tehe PCM.

Does anyone know the part numbers for the pins in the injector harness or the PCM harness? Any other suggestions?

Doug

 

[Wingback73]

All the smart people in this forum and no one knows the answer? C'mon folks, I just need a little help here

 

[macleanflood]

@Wranglerfix

New PCM time?

Check grounds?

-Mac

 

[CharlesHS]

Since the problem occurs primarily when you hit a hard bump; this correlates to movement by the wiring harness.
I would look at the PCM 32 wire harness that runs from the PCM along the firewall behind the valve cover and is routed around the rear right threaded head stud. The wiring harness insulation and split wire loom have been known to rub thru exposing the copper wiring which then causes the PCM communications to be interrupted (shorted to ground) as the wiring touches the threaded head stud.
My solution so this would not occur on my '01; installing a used rubber spark plug boot over the threaded head stud.

 

[Wingback73]

You both very much for taking the time to respond!

I haven't completely ruled out grounds yet, but since it only occurs on one of the cylinders, that felt less likely to be a root cause. I did do a visual inspection of the harness, didn't see anything that looked out of whack, but as we all know that doesn't mean there isn't a problem.

Mark has reached out regarding PCM wiring harness. My plan is to create a new set of wires specifically for cylinder 6 injector. If I still have a problem then the PCM gets replaced. If it goes away, I tear the harness apart and fix the wiring problem. Or more likely wrap some duct tape around my new wire and call it a day

Doug