I have a problem that I am running out of ideas.

I have an error code P0305 which is a cylinder #5 misfire.

I have tried a number of things to identify the problem. I tried switching ignition components between cylinders and the misfire stays at cylinder #5.

I also tried swapping fuel system parts around too. The misfire stays at cylinder #5.

I unplugged the #5 fuel injector and plugged in the #3 injector connector into the # 5 injector leaving the #3 injector unplugged. I got a code P0303 and a code P0205. So the misfire switched to the #3 cylinder and there is some sense that the computer recognizes no connection to the #5 injector wiring.

When everything was connected back to normal except for using a noid light, I found that there was no pulse to the #5 fuel injector. I checked the connectors at the fuel injector and at the computer and they both look fine.

I also checked the fuel injector connector has voltage when the ignition is on. I checked the signal wire with an ohmeter by pinning the connectors from the injector connector to the computer connector and it looks good too. I even tried to move the wire harness and wiring at the connector to see if I could make an intermittent problem, but it was always good.

I had a spare computer and swapped that out too. Even with the new computer, I still have a miss and code P0305.

I am running out of ideas. Anyone have other ideas on what to try checking?

Thanks

 

Did you ohm the injectors? Maybe a mouse nibbled a wire? Did your wires click twice and spark plug and wires good any sparks in the dark?

 

Yes, I did ohm the injectors and they were fine. I also had a couple extra, so I put in a different one in #5 with no improvement.

I worry about mice too. I don't see any evidence of it though. In addition, I checked from the computer connector pin to the injector connector pin and it was good even when I tried to work the harness and connectors around a little to see if I could make an intermittent problem show up.

I initially tried the ignition stuff. I swapped wires and there was no difference, still #5. However, with the noid light showing no pulse, I think it is somehow not getting the signal to the injector to fire it rather than an ignition problem.

Thanks for the ideas, I am still trying to figure this out.

 

Clean connectors on your opti and icm you can test the icm for free at the parts store. This is a strange one.

 

I agree it is a strange one.

I am not sure how cleaning connectors for the ignition or the ignition control module would cause no pulse on one fuel injector? Are they related in some way? Does the computer use inputs from the ignition to sequentially fire the fuel injectors, or cause one injector to not fire?

 

What year car are we talking about ??

 

I thought that all P0XXX were very generic codes and not OE specific and the P0305 in that case would hint ignition (wires/plug etc). The fact that yours didn't travel maybe hints that being correct.

The P0205 when you displayed that would be expected with your swapping I'd think of components. The P0303 is a "stumper" under your swapped connections etc.

P02 - fuel & P03 electrical I thought for generic OBD2

P0300 diagnostic tree is pretty damned extensive, is there or has there been any accompanying DTC?

Is this an LT1 or LT4 '96?

Can you do "freeze frame" with your scanner and monitor "misfires" while driving?

 

Thanks for the help guys.

I found the problem was a fuel injector connector socket was not making good contact to the pin. So when I probed the connector to connector, everything checked good, but probing the connector didn't simulate the actual fuel injector pin to the connector. In short my ohm meter test made contact while the fuel injector did not.

Thanks again.

 

Good job.