My check engine light is on and I've cleared the ECU/ECM and it comes back with code 51: "Fuel Injector circuit open" I've read that the resistance should be like 10-14 ohms, but my reading are way off from that. I couldn't get the connector off any of the fuel injectors and the rubber boot was alread brittle and breaking so I was able to get my meter probes in there to measure and I got different reading from each injector (#1= 3 ohms, #2=in-accessable, #3= 2 ohms, #4= 50 ohms, #5= 1.7 MOhms, #6= 1.7 MOhms)
I'm looking for some troubleshooting techniques/tips to test each injector to see if it may be bad.

The symptoms I'm getting right now is that it idles very rough, accelerates sluggish and has had poor gas mileage the past few months.

 

new or rebuilt injectors will measure 12 Ohms. forsure your #5 & #6 are dead and I'll bet you'll wish you had boots no top of those connectors. btw there is a small wire clip that hold the connector on the injector

 

Is it possible then to remove the connectors without having to pull the top manifold?
I've measured each of the injectors resistances in circuit (since I couldn't pull the connectors) with a multimter. Also, I checked the voltage and looks like a constant +12v on one wire of each injector, then I looked with a scope and also saw +12 on each side, but the left wire had negative pulses that would increase with acceleration so I guess the signal is getting to the injectors. I'd still like to be able to do tests with connector off though!

 

YES, you can remove the fuel injector connectors without removing the top manifold.

There is a small metal clip (Shaped like a "U") that slides around the connector. Just use a small flat tipped screwdriver or a pick to start to slide the metal clip off the connector. Then I usually use a pair of needle nose pliers to pull the clip off the rest of the way so I don't drop it.

You should definitely Ohm out the injectors with the connectors removed before you decide to replace anything. I'm not sure your getting a true reading of the resistance of the injector if you’re measuring the Ohms with the connector still on the injector.

 

I agree with tool. Since your boot were already briddle and/or breaking, You may find that you have build up in the connector that is causing an poor or open state in your circuit.