P0202 code but injector is okay

[Blue Maltese]

Apologies for reviving an old thread, but after hours of searching various sites and threads, I keep coming back to this one because it seems like I am having potentially the same issue. 2006 LJ 4.0 automatic with 175k threw a P0302 and P0202 code the other day. I've owned the jeep for about 40k miles so pulled and replaced the plugs with new Autolite XP985s, cleared codes and restarted. P0202 popped back up immediately and the P0302 shortly after. Listened to all the injectors (screwdriver stethoscope) and #2 clearly is not working. Checked ohms on all 6 and they are all consistent leading me to believe that the specific injector is not the problem. Following Blue Maltese's post above, I checked the wiring harness for wear and found nothing that would indicate a possible break or short, even at the contact point behind the valve cover where it commonly occurs. Next thing I attempted to do is check the ohms between the PCM and the specific injector as stated above, but am not well versed when it comes to wiring and am not sure I am testing it correctly. Can anyone explain how I would test that circuit? Do I connect the multimeter leads to the two female sides of the wiring connector for that injector? When I do, I get 0 ohms which could be a good thing, or could mean I'm not testing it correctly.

Thanks for any help anyone can provide.

You've got this LJNV, you can do this. Look at the wiring diagram for the ECM (PCM). Don't get overwhelmed. That Engine Control Module sends a pulse out to the injectors to spark them. Just look at the diagram to see which color wires to check for a pulse. You could probably even use a voltage tester to see if you are getting the pulse. By voltage tester I mean one of those screwdriver shaped lights with a needle like probe and a wire you attach to a ground. The light in it will light up when the needle touches 12V. If you're getting the 12V pulse, then that's not your problem. You probably aren't getting fuel to that cylinder. No pulse? Get a new ECM. Got 12v pulse? Bad injector I would guess. Cylinder 3 is notorious for having "Heat Soak" issues. If the heat shield between the fuel rail and exhaust manifold is worn thin, the heat off the manifold will boil off the gas in the fuel rail. This doesn't sound like your problem though. It would be rough idle for a little bit, but then run okay once the gas started flowing in okay.
Let's take the overwhelming broad view of confusion away and just look at it simply.
you have a green and tan wire going to injector 2. the green is 12v power and the tan is the ECM telling that injector to fire.
The tan wire connects to the ECM at terminal B15. Disconnect the tan wire and see if you are getting a signal from B15. Hook your meter positive lead to the battery positive, and hook the meter black lead to B15. With the engine running you should get a 12v volt signal to your meter. It will pulse. If you don't get a pulsing then your ECM is bad. (or your green or tan wire is bad). You can disconnect your wires to check ohms from end to end for continuity to see if they are good.
Now here's the disclaimer. I'm not a mechanic and I'm 95% sure this will work for you. It did for me.
Either you will fix the problem, or it will still be a problem when you're done. No down side to trying.
Good luck.

 

[LJNV]

You've got this LJNV, you can do this. Look at the wiring diagram for the ECM (PCM). Don't get overwhelmed. That Engine Control Module sends a pulse out to the injectors to spark them. Just look at the diagram to see which color wires to check for a pulse. You could probably even use a voltage tester to see if you are getting the pulse. By voltage tester I mean one of those screwdriver shaped lights with a needle like probe and a wire you attach to a ground. The light in it will light up when the needle touches 12V. If you're getting the 12V pulse, then that's not your problem. You probably aren't getting fuel to that cylinder. No pulse? Get a new ECM. Got 12v pulse? Bad injector I would guess. Cylinder 3 is notorious for having "Heat Soak" issues. If the heat shield between the fuel rail and exhaust manifold is worn thin, the heat off the manifold will boil off the gas in the fuel rail. This doesn't sound like your problem though. It would be rough idle for a little bit, but then run okay once the gas started flowing in okay.
Let's take the overwhelming broad view of confusion away and just look at it simply.
you have a green and tan wire going to injector 2. the green is 12v power and the tan is the ECM telling that injector to fire.
The tan wire connects to the ECM at terminal B15. Disconnect the tan wire and see if you are getting a signal from B15. Hook your meter positive lead to the battery positive, and hook the meter black lead to B15. With the engine running you should get a 12v volt signal to your meter. It will pulse. If you don't get a pulsing then your ECM is bad. (or your green or tan wire is bad). You can disconnect your wires to check ohms from end to end for continuity to see if they are good.
Now here's the disclaimer. I'm not a mechanic and I'm 95% sure this will work for you. It did for me.
Either you will fix the problem, or it will still be a problem when you're done. No down side to trying.
Good luck.

Thank you Macleanflood and Blue Maltese for the feedback. Had a little time today and was able to get a noid light to test the #2 connector. It did NOT light up. I pulled and tested several other injector connectors and it DID light up correctly on all of them. I then connected the multimeter to a ground and checked the voltage to the #2 connector. It showed 14.3 volts on the right receptacle and 0 on the left. Checks on other connectors showed the same results. So from those two tests, it would seem connector #2 is getting power but no pulse from the PCM. I am guessing that before I can be sure that the PCM is the problem, I need to test that tan wire from the computer to the injector for continuity, correct? (I have an '06 and the wiring diagram is different from the one Blue Maltese posted. In my case the "tan" wire is BR/DB and instead of terminal B15 it states just 14. Now I'm having difficulty figuring out exactly where terminal 14 is located. None of the plugs connecting to the PCM have terminal labels. I believe C2 is the second plug from left (of the 4), but how are the terminals arranged? Top to bottom, left to right or something else? Nevertheless, I think I'm making some progress and appreciate the help!

 

[macleanflood]

Good work.

Let me look through the FSM...sure someone else with direct experience with those plus can answer.

Tying in @Wranglerfix JIC you want to send your PCM in for testing.

-Mac

 

[Blue Maltese]

Thank you Macleanflood and Blue Maltese for the feedback. Had a little time today and was able to get a noid light to test the #2 connector. It did NOT light up. I pulled and tested several other injector connectors and it DID light up correctly on all of them. I then connected the multimeter to a ground and checked the voltage to the #2 connector. It showed 14.3 volts on the right receptacle and 0 on the left. Checks on other connectors showed the same results. So from those two tests, it would seem connector #2 is getting power but no pulse from the PCM. I am guessing that before I can be sure that the PCM is the problem, I need to test that tan wire from the computer to the injector for continuity, correct? (I have an '06 and the wiring diagram is different from the one Blue Maltese posted. In my case the "tan" wire is BR/DB and instead of terminal B15 it states just 14. Now I'm having difficulty figuring out exactly where terminal 14 is located. None of the plugs connecting to the PCM have terminal labels. I believe C2 is the second plug from left (of the 4), but how are the terminals arranged? Top to bottom, left to right or something else? Nevertheless, I think I'm making some progress and appreciate the help!

Good job LJ.!! Sorry my wiring doesn't match up with yours. I spent hours searching before I finally found that wiring diagram on the internet. You're right about that "Tan" wire needing to be checked. Just ohm it to make sure it's not broken somewhere. I hope that's your problem, the ECM cost about $500 to replace. I got mine from Flag One. I sent them my VIN number and they programmed it. I just had to mount it and plug the harness back in. It's been a couple years now. Still working good. I tore my bad ECM apart to see if I could repair it to keep as a spare, but it was above my skill level. So I threw it away. Later I found out old ECM's can be sent in for credit. Good luck and get dirty soon.

 

[Wranglerfix]

@LJNV Good morning from south Florida. I can test your pcm if you would like to send it into us and turnaround time is 48 hours!

 

[LJNV]

Thanks for everyone's input and feedback. I took a gamble and rolled the dice on the 2nd PCM plug from the left (when staring at it from the front of the jeep) to be the "C2" plug. Removed the plug, removed the "cover" off the back of the plug, peeled back the tape wrapping the wires together and not only found the BR/DB wire from injector #2 but also discovered that the pin holes are actually labelled on the back of the plug where the wires enter the pin holes. Sure enough, the BR/DB wire was inserted into pin #13 as stated in the wiring diagram for the '06. A continuity test on that wire (from C2 pin #13 in the PCM to the #2 injector plug) failed, revealing a break in that wire somewhere. Guessing I would probably never find the break, I then peeled back a bit more tape on both ends of that wire to give me something to work with, then cut the wire at both ends about 2 inches from each plug. Grabbed some 18 gauge primary wire and threaded it through the engine compartment along the existing wiring, then soldered it to the 2" ends that were sticking out of the plugs to effectively replace the broken wire. Tested the new wire for continuity and it passed. Plugged the C2 plug back in, inserted the noid light into the injector plug and started the jeep. The noid light flashed as it should. Shut the jeep off, cleared the codes, removed the noid light and reconnected the injector plug to injector #2. Started the jeep and success! No misfire, no rough idle, no codes. Took it for a test drive and its all good. Protected the full length of the new wire with sleeve and zip tied it to the existing harness. Wrapped the C2 plug wires back up with electrical tape and reinstalled the plug "cover". Done. Problem solved! Thanks again to all those that reached out and participate on this forum. Don't think I could have resolved this one on my own. Thank you.

 

[macleanflood]

We call that repair technique a overlay.

I'd bet good money you'd find the break at the back of the valve cover.

I'd also bet you'd find wires that are close to parting ways.

Good fix! Way to stick to it!

-Mac

 

[Blue Maltese]

Thanks for everyone's input and feedback. I took a gamble and rolled the dice on the 2nd PCM plug from the left (when staring at it from the front of the jeep) to be the "C2" plug. Removed the plug, removed the "cover" off the back of the plug, peeled back the tape wrapping the wires together and not only found the BR/DB wire from injector #2 but also discovered that the pin holes are actually labelled on the back of the plug where the wires enter the pin holes. Sure enough, the BR/DB wire was inserted into pin #13 as stated in the wiring diagram for the '06. A continuity test on that wire (from C2 pin #13 in the PCM to the #2 injector plug) failed, revealing a break in that wire somewhere. Guessing I would probably never find the break, I then peeled back a bit more tape on both ends of that wire to give me something to work with, then cut the wire at both ends about 2 inches from each plug. Grabbed some 18 gauge primary wire and threaded it through the engine compartment along the existing wiring, then soldered it to the 2" ends that were sticking out of the plugs to effectively replace the broken wire. Tested the new wire for continuity and it passed. Plugged the C2 plug back in, inserted the noid light into the injector plug and started the jeep. The noid light flashed as it should. Shut the jeep off, cleared the codes, removed the noid light and reconnected the injector plug to injector #2. Started the jeep and success! No misfire, no rough idle, no codes. Took it for a test drive and its all good. Protected the full length of the new wire with sleeve and zip tied it to the existing harness. Wrapped the C2 plug wires back up with electrical tape and reinstalled the plug "cover". Done. Problem solved! Thanks again to all those that reached out and participate on this forum. Don't think I could have resolved this one on my own. Thank you.

Thanks for the update. You're an inspiration to others now.

 

[Mdjmartinez]

Apologies for reviving an old thread, but after hours of searching various sites and threads, I keep coming back to this one because it seems like I am having potentially the same issue. 2006 LJ 4.0 automatic with 175k threw a P0302 and P0202 code the other day. I've owned the jeep for about 40k miles so pulled and replaced the plugs with new Autolite XP985s, cleared codes and restarted. P0202 popped back up immediately and the P0302 shortly after. Listened to all the injectors (screwdriver stethoscope) and #2 clearly is not working. Checked ohms on all 6 and they are all consistent leading me to believe that the specific injector is not the problem. Following Blue Maltese's post above, I checked the wiring harness for wear and found nothing that would indicate a possible break or short, even at the contact point behind the valve cover where it commonly occurs. Next thing I attempted to do is check the ohms between the PCM and the specific injector as stated above, but am not well versed when it comes to wiring and am not sure I am testing it correctly. Can anyone explain how I would test that circuit? Do I connect the multimeter leads to the two female sides of the wiring connector for that injector? When I do, I get 0 ohms which could be a good thing, or could mean I'm not testing it correctly.

Thanks for any help anyone can provide.

I had P0202 & P0302 pop up today. While driving (2000 TJ 2.5L), check engine light came on and caused a huge back fire, sputtering, and almost loss of power.

I read the codes, checked them in the manual, and it said cylinder 2 misfire or open injector circuit.

Neither were the issue, it was my ground cable on the firewall from the hood to the motor. It was loose. Pulled the negative & positive cable, tightened the grounds. Checked the others. Reconnected the battery cables. Bam. Code gone, Jeep runs like nothing ever happened.

I know this is an old post, hope it helps!