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Fault Code 51 on my 1992 Pathfinder SE


microfiz
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Hi, new to the forum and figured I could use your experience and help. I've owned my V6-SE Pathfinder for over a year now and put 30,000 commute miles on it (it now has 230,000 miles). It's been very reliable and I am happy with it so far. However, my car engine light just went on a couple of days ago and immediately the car idled rougher. The diagnostic mode showed code 51 (ignition circuit) and after googling that problem, I went ahead and did the following:

1) ohmed out the injectors- I was getting more like 12-13 ohms instead of 11-12 when cold, but that could be due to my cheap multimeter

2) replaced one of the corroded connectors

3) swapped out one injector with questionable terminals (partially broken)

4) new fuel filter

5) sanded ground terminals (the ones attached to the intake plenum)

 

However, the fault code is still there and the engine idles a little rougher than it did before the code. I have not checked the fuel pressure yet. Could a worn our fuel pump cause this code? Bad fuel pressure regulator? Electrical? Your ideas are welcome.

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  • 2 weeks later...

Just to close the loop, I fixed the problem. I ohmed out the six injectors though this harness diagram (from a thread here):
http://s321.photobucket.com/user/lck403/media/plugs.jpg.html

 

Note: the common pin is not the one highlighted on the picture... I think it's on the opposite end... but just move the terminal until you get continuity.

 

Injector #4 read open so I swapped it out with an injector from the junkyard. It was marked black when mine was blue... didn't have a choice so I ignored the forum warnings and installed it. Codes are gone, it idles and runs great now. Thanks to this forum... =)

Edited by microfiz
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  • 6 months later...
  • 2 weeks later...

I have the same code 51, on my 94 pathfinder. I have gone through the procedure for testing the injector circuit, and found about a 1.2v drop on the 2,4,6 side, and further inspection found that my #6 injector ohms out at 14.4, and all the others were about 12.8. Could that one injector be the cause of my voltage drop on that side? The other thing that I found funny is, that when doing the power bank testing (I think that's what it's called), the #6 cylinder did stumble just like all the others when I pulled the plug wire. The truck still runs smooth, but I have been getting crappy fuel economy lately. Crappier than normal. I also tested the MAF, TPS, IACV, and O2 sensors according to the procedures, and all of them test good. The truck got a tune up when I first bought it about a year ago, plugs, cap, rotor, wires, fuel and air filters, and also a new radiator. I also am planning on tackling the passenger side exhaust manifold leak this weekend. Looks like a PITA.

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One thing I learned on our 1999.0, the faulty injector Ohm'd in the correct range, but failed once warm and didn't cause issues until being shut off and restarted (while still warm). Just saying incase you don't find a smoking gun right away...

 

I doubt a few Ohms would cause it to 'fail', but I can see how it might cause more/less flow than normal. Unless an injector has completely failed, the plug wire test will still cause a stumble, even a crappy running cylinder is better that a dead one...

 

Manifold leak repair can come in all flavors so don't assume, just find out what you are dealing with first.

Yes, the most common flavor is 'suck', but maybe you are lucky. :shrug:

 

B

 

 

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Thanks. I did find the timing off a couple of degrees too, so that may be where my fuel economy has gone, along with the crappy winter gas we have to use. As for the exhaust, I already did the driver's side, and that wasn't much fun. There is even less room on the passenger side, so it should be fun!

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