2005 jeep liberty # 4 injector , no fire .

[Logan Savage]

I have a 2005 3.7 Liberty & I have a code for # 4 injector . I have definitely narrowed the problem down to no ground signal from the pcm for that injector . I traced the wire from the injector to the pcm connector , bared a small spot in the wire just outside the pcm connector & there is no ground signal coming out of the pcm on that wire .
Does this definitely condemn the pcm or could something else cause the pcm to not send out a signal for one injector only ? I suppose it's possible , but I think highly unlikely that the problem could be in the pcm connector itself . I have had it unplugged & the connector & pin both look ok .

 

[teeje]

Take a multimeter and test a known good one and switch it with the bad one and see what you get. Usually when this happens, the injectors short on the inside. Go there first and let us know


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[DirectxLiberty]

2002 Liberty Limited

Rebuilt engine due to cylinder #2 intake valve seat falling damaging piston and cylinder head. I check timing 6 times before putting engine back together. Put engine back into jeep last weekend. Started engine, got engine light on. Check codes, I got pass side bank ignition coils with no power to them, cylinder 2, 4, & 6. Has anybody had or heard of such?
I ordered the factory shop manual today to verify wiring from ecu to coils but it's a week away before it's arrival. Open to any suggestions.
Thanks in advance.

 

[Logan Savage]

The first thing I did was swapped injectors , same problem , then I started checking wires , I verified one wire to the injector had power & then I verified continuity on the ground wire that goes from the injector to the pcm . Just to completely satisfy myself I bared a small spot in the ground wire right at the pcm . No ground signal coming out of the pcm .

 

[belvedere]

Sure sounds like the PCM to me. I can't think of any other troubleshooting than what you've already done.

 

[renegade 04]

If it turns out to be the ECM, you can buy a new one programmed from places on the web.

 

[mx3_ryder]

I wasn't getting a signal to #2 injector when my engine dropped a valve seat and lost all compression. I was told by a mechanic the computer will cut power when it detects somethings wrong to avoid further damage. Have you checked compression?

 

[Logan Savage]

Compression is good .