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Daniel Wilson
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2003 2500 4x4 duramax 6.6l. Misfiring on cylinders 2-4-6-8.

Customer Question

2003 2500 4x4 duramax 6.6l. Misfiring on cylinders 2-4-6-8. Have changed those 4 injectors, inspected wiring harness and all plug connectors. Runs fine for first 2 mins after cranking, then misfires complete driver side bank. Power on both pink wires at ficm.
Submitted: 4 months ago.
Category: Chevy
Expert:  Dan replied 4 months ago.

Hello,

A common problem is the big plug that all of the coil packs tie together to which links it to the rest of the harness. I would inspect grounds for that section of the harness along with the fuel injector portion.

Plugged Cat on that side. This would make an entire bank misfire as well.

Please reply to this if you need more help. If you are satisfied with my service, please rate at the top of the screen. Rating does not close out your question. Remember, sometimes it is difficult to completely diagnose your vehicle without being there, but I will try to give you the best answer I can. If I am not giving you 5 star service, please let me know what I missed.

Thanks,

Dan

ASE Master Technician

Customer: replied 4 months ago.
This is a Diesel engine
Expert:  Dan replied 4 months ago.

Yes I know it is a diesel engine, you have misfires on an entire bank on the drivers side. Have you check the catalytic converter on that side?

Have you had this scanned for codes?

Customer: replied 4 months ago.
Codes are po302,304,306,308, and po380. No dual converters on these engine. Exhaust leaves manifolds into up pipes for turbo and out to single exhaust
Expert:  Dan replied 4 months ago.

A timing issue could affect an entire bank.

I am afraid I am not going to be much help on this, I am going to opt out another expert will help you shortly. Please do not reply to this message because it will lock this question back to me.

Expert:  Edgar replied 4 months ago.

Hello my name is ***** ***** I'll be happy to help you today, if you have power on the two pink wires of the FICM ckeck also the ground wires on the FICM they are the black/yellow wire and the black/green wire make sure you have good ground on those, if the power and ground on the FICM are very good then make sure all the connectors on the injectors on that bank are good and secure which I see you already did if everything is good and secure and there are no other grounds on power wire in the vehicle loose, with the engine running try to check if there is power in the orange/black wires on each injector of that bank that is misfire but check for power while the engine is missfiring on that bank, if there is no power on orange/black wire on each injector while missfiring then the problem is internal in the FICM and is not supplying 12 volts for the injectors on that bank, you will need to replace the FICM.

Customer: replied 4 months ago.
Grounds are good at ficm ( black/yellow - black/green ). Check voltage while running and misfiring where engine harness plugs to injector harnesses ( orange/black - orange/white ) at both plugs , voltage on all wires are ranging from 20 to 24 volts
Expert:  Edgar replied 4 months ago.
The voltage is too high, it should be around 12.0 volts, do each wire read 20 to 24 volts? How about the voltage on the bank that is not misfiring are they the same voltage 20 to 24 volts? Try to connect a test light between the orange/white and the light green wire on injector number 2 and see if the test light comes on and off and how bright is it and compare it to one of the other injectors on the bank that is not missfiring
Customer: replied 4 months ago.
I'm checking with a volt meter. 20 to 24 volts probing orange/white to battery ground, same voltage reading on both banks. Probed orange/white and light green on cylinder 2, no voltage. What color combo on cylinder 1, different color wires.
Expert:  Edgar replied 4 months ago.
Cylinder number 1 wires are orange/black and light green/red
Customer: replied 4 months ago.
Cylinder 1 orange/black and green/red, no voltage. Engine running, cylinder 1 orange/black probe and probe to battery ground 21 volts. Engine switched on not running green/red probe and probe to battery positive 11.68 volts
Expert:  Edgar replied 4 months ago.
Try to do the same measurements that you did on cylinder 1 do it on cylinder 2 and 4 to see if the measurements are different cylinder 4 wires are orange/black and light green/white and can you let me know what are the measurements?
Customer: replied 4 months ago.
Probing harness on cylinders 2&4 are same as cylinder 1. No voltage between harness wires, only when I probe harness wire and ground=21 volts. Probe other harness wire and positive battery=11.89 volts. I assume the 21 voltage wire in harness is voltage in and 11.89 wire is ground. All cylinders the same. I don't get DTC on 2-4-6-8 until it runs for several minutes. Cut out cylinders and 1-3-5-7 are strong, I can here slight change in engine when cut out 2-4-6-8. It's like they are firing but very little. I have a glow plug fault code and barometric pressure sensor fault as well
Expert:  Edgar replied 4 months ago.
It looks to me that the wiring is good according to the information you provided, can you check for battery voltage at the glow plugs on cylinders 2,4,6,8 with the switch on? At this point Is either a glow plug issue or what I'm suspecting which could be the ficm, I had so many cases like yours and ended up been the ficm but I would like to make sure everything test good
Customer: replied 4 months ago.
When I replaced 2-4-6-8 injectors, I replaced glow plugs on that bank. I have even taken the control wires off both banks glow plugs and completely unplugged glow plug controller. What's odd to me on this one is if it is the ficm, why did it pick 2-4-6-8. Usually what I've seen when ficm burns out is it burns one side, cut fire to random cylinder back and forth across the engine the way the ficm fires. I will search the glow plug circuits again. They only other thing is the gas gauge doesn't work, but I can't see how that would cause this problem
Expert:  Edgar replied 4 months ago.
It is very odd and I have seen ficm cutting one bank, and looking at all my information everything you have done is right, wiring harness good, injectors good,no loose connection, you may want to take a look at the two connectors on the driver side of the engine connector c107 and c108 they are on the top driver side close to the turbo, disconnect both of them and check the terminals sometimes the terminals back out
Customer: replied 4 months ago.
I have checked those connectors. Is there any additional test that I can do on the ficm to get a better feeling than just replacing it. I do not have a test ficm.
Expert:  Edgar replied 4 months ago.
There is one more thing that May cause also that issue, the ficm connector harness rubbing on the back of the alternator, the alternator bracket or the harness retaining bracket which will cause then conduit rubbing through exposing the wire and chafing the wire insulation, you have to disconnect the ficm bend it up and backwards away from the ficm and take a very close look at the wires
Customer: replied 4 months ago.
I've unplugged ficm and unsnapped the complete harness looking for rubbed or broken wires, no luck. All wires look fine
Customer: replied 4 months ago.
Not ficm, just test with ficm from another lb7. Still same symptoms. Any ideas, only 3 harnesses left. Engine harness and 2 injector harnesses
Expert:  Edgar replied 4 months ago.

I apologize for the delay you will have to check then ohms on the harness from ecm and from ficm to injectors and to the injectors, but let me put the question back in the list to see if another expert can help you, do not reply to me because it will keep me lock in your question.

Expert:  Daniel Wilson replied 4 months ago.

Hi my name is***** will be glad to help. What is the serial number Duramax? LLY?

Expert:  Daniel Wilson replied 4 months ago.

P0380 code means that the PCM has detected a fault in the glow plug/heater circuit "A".

Potential causes for this DTC may include: Fault in glow plug wiring (open, short to ground, etc.)

Glow plug faulty

Open fuse

Faulty glow plug relay

Faulty glow plug module

Click this link below for the 301-308 troubleshooting and diagram. Let me know if there is trouble accessing the file

Toubleshooting

Customer: replied 4 months ago.
I am in the process of repairing the glow plug issue to remove that fault code. As of right now you can read back through posts and see the tests I have performed. I tested yesterday with known good ficm and still same problem. This is a 2003 lb7 duramax. I will return updated info after glow plug repair.
Expert:  Daniel Wilson replied 4 months ago.

Thanks for the update. That narrows things down to either a harness problem or failed injectors which will cause the FICM to shut down the problem bank. I see you changed the injectors already as well. Were these new, used, or reman? I would take a closer look at the wiring harness and run some continuity checks. Let me know

Customer: replied 4 months ago.
Good brand remand. Finishing up glow plugs now. Pretty much to my knowledge there is on 2 things left, the 2 left bank injector harnesses or the main engine harness. Question, is it possible the truck ecu would cause this. I can't see how, but has anyone ever seen that. Thanks.
Expert:  Daniel Wilson replied 4 months ago.

Most likey it will be a problem in the harness but it could be possible and ECM issue if you have confirmed all other possibilities we went over here. See if you can obtain a test ECM or have the existing one reflashed/reprogrammed and see if it will successfully take a reflash.

Customer: replied 4 months ago.
I used the test ficm from another truck that runs fine, can I used the ecm from that truck as well or are they vin matched.
Expert:  Daniel Wilson replied 4 months ago.

As long as the other truck matches all options to the tee it would be okay but it is best to program for your VIN to avoid any headaches.

Customer: replied 4 months ago.
Other truck is an 01 with more options.
Expert:  Daniel Wilson replied 4 months ago.

usually swapping an ECM is okay for test purposes but you should always have the programming done to match your truck

Customer: replied 4 months ago.
Glow plugs repaired, 8 new glow plugs and new controller relay. All codes cleared. Cranks and runs great for 5 to 10 mins, then 2-4-6-8 misfires. Can run truck for a good while before codes show up. Is there a wiring schematic and wiring harness test I can perform to see if harness is the problem. Thanks
Customer: replied 4 months ago.
Is there anyone at justanswer that can assist me with my problem. No response?
Expert:  Daniel Wilson replied 4 months ago.

Hi, Sorry for the delay. Experts are not employees of the site. I help on here in between jobs as time allows. I have been out on the road this week and will be tomorrow as well. Use an OHM meter to test pin to pin for continuity of the harness. should be close to zero OHMs for a good reading of continuity. Click on this link I uploaded for you and see PDF page 75 on for the diagrams and pinouts. Let me know

Schematics

Expert:  Daniel Wilson replied 3 months ago.

Hi, Did you get this resolved?

Customer: replied 3 months ago.
I did, nothing electrical, found cp3 pump coming apart and the metal had stopped up the valve bank where fuel pressure sensor is leading to left bank injectors. Replaced cp3 pump and cleaned fuel system. Thanks
Expert:  Daniel Wilson replied 3 months ago.

Thanks for the update and glad to you got this resolved.

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