Engine Code 27 HELP please

First I would like to say that i have searched and can't find what information I need

I have a check engine light with the code #27 being thrown. Code 27 has two parts. 1. Injector control Circuit--bank output driver stage does not respond properly to the control signal 2. Injector No. 1,2 or 3 control circuit and peak current not reached.

This is causing sporadic rough idle and sporadic running rough under light throttle. IT smooths out when I stomp the pedal but laws forbid me to dive like that all the time.

I need some help here. I have taken a ohm meter to the 1, 2 and 3 injectors and all read the same... open circuit. What is causing this and what can I do to get rid of this problem?

Bump BTT

Can anyone help me on this? I'm getting ready to pull the injectors and fuel rail and send the injectors in for testing if nobody can help me on this.

Bump

Before you pull the injectors, I suggest you check the wiring harness very carefully. You don't state the year, but I have had harness problems on a 93, and others have had similar problems.

On the mopar (91-up) system, the computer switches and fires the negative side of the injector circuit, and the positive is provided through the ignition circuit, via a series of splices, to each injector. A bad splice or poor connection will cause similar symptoms and codes. Look first at the positive side, because the splices are a source of potential problems. This is especially a suspect if you notice that the problem gets worse as the engine heats up, or misbehaves worse when you start soon after being parked hot.

First thing to do is simply to visually inspect the connectors. See if you can get a stethoscope on the injectors when it's misfiring and try to spot if one is not clicking properly.

You can test for a missing injector by running the engine at idle, and pulling injector connectors, one at a time (plug back in before pulling the next, etc.). If you pull one that is working, the engine will bog a little, then recover. If you pull one that isn't working, you'll hear no change at all.

If you find one that is dead, the next step is to swap the harness connection for that injector with the one nearest to it. Now repeat the test. If the fault follows the injector, you have a bad injector. If the fault follows the harness, you have a bad harness.

Now, if you find a bad harness, the best thing to do is to get a good and sensitive digital volt and ohm meter, and start testing. You might be able to detect low positive voltage at the bad connection. If that is the case, the cheapest and best solution is to slice open the harness, and simply bypass the splices - route the bypass from the connector to the furthest-upstream, wire of the same color in the harness. Solder the splice.

If the fault is between injector and computer, you'll need to find out for sure if the fault is in the harness or the computer, but again, you're probably better off just bypassing than replacing whole harnesses.

If your Jeep has the kind of injector connectors that use a wire clip in the plug, it helps to remove all 6 wire clips before you start testing. If you don't, you'll have to yank and wiggle and run the risk of opening up an injector leak. You can run it, and even drive it, that way for a while while you're testing.

Soory.. I forgot to list the year it's a 92.Thank you for the responce. I am sad to say that I have pulled the injectors and shipped them off for cleaning and testing. This gives me a direction to go in when they get back.

Is there a way to test the harness without the injectors?

Bump
IS there a way to test the injector connectos without the fuel injectors in place.?

Onkover said:

Bump
IS there a way to test the injector connectos without the fuel injectors in place.?

Click to expand...

You can test the harness with an ohmmeter. Make sure the ignition is off for that, and set the ohmmeter for the lowest resistance reading (ohms, not Kilohms or megohms). Short the ohmmeter leads together, and note the reading, which may be fractional ohms. The meter is reading the resistance of its own fuse. This reading is what you should see when you measure a plain wire for continuity, if you get good probe contact. There should be no appreciable increase in resistance. When you hold the ohmmeter leads apart, this is an open circuit (infinite resistance) and this is what you should see whenever you are probing something which should NOT have continuity.

The positive line from each injector goes from the connector back through the harness, to the connector at the ignition coil, as I recall (sorry, my 95 FSM is out in the shop and it's below zero outside, so memory for now). You should be able to get it from the wire color. There should be no measurable resistance. A few ohms resistance can be enough to cause injector misfiring. the negative lines go from the injector connectors individually to connectors on the PCU. I don't have the diagram on hand, but you may be able to figure it out. I think faults are less likely here than in the positive line with all its splices.

In addition to continuity you can probe the harness for leaks and shorts. First probe each connector between positive and chassis ground. It should be infinite resistance (open circuit), as far as I know. There may be some high resistance circuit path to ground through the ignition system, but it should not show on the X1 ohmmeter range unless your meter is auto-ranging. The main thing to watch for is that all connectors read the same. Then check the terminal pair on each injector for leakage between positive and harness ground lines to the PCU. Again, there should be no circuit at all. Finally, check between harness negative (PCU line) and chassis ground. That should also be open circuit.

Beyond that, I think you will have to wait until the injectors come back.

The harness can be tested while running, using electronic testers, or individual "noid lights" which detect the injector pulse. A failure of this test should be considered pretty definitive. However, I found that on the 93 I struggled with a few years ago, the tester detected voltage that was too low to fire the injector, thus missing the bad harness splice, so a pass may not be as definitive as a failure.

I have followed your advice to a T. I did find that the #6 cly harness wasn't giving a reading at all and repaired the line further up in the harness.

I have a crappy meter and will be going to buy a better one and do all this again.

THANK you Matthew For your help so far. I hope this was the issue and will post up either way.

I have got a better meter and re-run all tests. I can't find anything. This is getting frustrating. I now have another issue. The Jeep is now due for smog and will not pass with the light on.. sure I can pull the bulb but I sure wish I could find this. The injector harness is hard as rock. Just taking it apart is hard to do without damaging the wires. IN this porcess I did find what appered to be a old repair. I cut away the old stuff and redid the connection and hoped for the best but still having issues.

Hey there,

Did you get this resolved? I have a 94 w/ 132k and have been having the same problem?

thanks.

Good Morning Bump.