Intermittent code 61 - harness/injectors replaced - NOT fixed

Hey Guys,

So I have 1999 Freightliner Century 12.7 series 60. Keep getting an intermittent CEL and code 61 (on cylinders 1, 3, 5) which results in engine misfire/loss of power.

I had a Freightliner dealership replace all 6 injectors and the injector harness at the cost of $4500. I get the truck back and issue still happening. It will run with misfire/loss of power for approximately 5-10 minutes and return to running good. Any ideas it could be?

Thank you for any help.

 

Thank you for the response JB7. I went to Freightliner today to get some tools out of the truck and advised the mechanic of the troubleshooting steps you sent me. I recently just replaced the alternator, and the first step in the process is check alternator ground. The mechanic stated today he checked ECM ground and they will be doing an roadtest tomorrow, and then a dyno after that. Seems different than the troubleshooting process.