'01 3500 LB7 P0202 P0203 P0205 P0208 P1262 LB7 Issue after head gasket replacement

Samisunjp

New member
Sep 5, 2025
28
6
3
North Carolina
Okay, so to update this thread in case anyone comes across it later looking to try to solve these codes.


Truck runs! No codes.

I put it all back together and I’m leaning towards what 2004LB7 said, a loose, or not tight enough nut on the injector harness under the valve cover.

Here is everything I have done or changed:

Rebuilt FICM (Had two working and both threw codes so don't believe it was this)
New engine wiring harness. (old one tested fine with no breaks on any wires so it wasn’t this)
New fuel filter housing (old one was working fine without leaks, only changed this because I was doing head gaskets)
Re-checked all grounds (Didn’t change anything with them before putting it back together so don't believe it was this either)
Checked ohms and inductance at all injectors (they were all within spec)

Only thing I can think of was a loose nut on one injector itself.

No codes and can now see balance rates without issue.


Going to do some test drives tomorrow to make sure everything truly is good. I will update tomorrow.

Thanks to everyone for all of their input and help.
 
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