Misfire at 1200rpm

[HDdave]

Alright, this one is starting to get the best of me. 2016 LML, 160k. Cracked a piston at 145k, put in fresh rebuild (Callies crank, mahle pistons, studs, cp3 swap). Everything was great for 6 months or so, then my head of construction who drives it came to me and said he thought the transmission was doing something weird. I didnt even bother to take it for a spin at the time, because it had a p0700 and I know the TCM's can be prone to fail around that mileage- so I just replaced the TCM with a new one.

That got me nowhere, so I drove it for a day and pretty quickly figured out its some kind of misfire that occurs only at 1100-1200 rpms. Does it in park, neutral, drive whatever... I checked all of the grounds on the truck seeing as the engine was swapped, found one loose one we forgot to tighten up on the drivers side of the engine block.. Fixed that, got no results. Have been told to search for harness rub through, so far I have not found anything at all. So I got pissed off and just wound up buying another truck for the company to keep us on the road.

The truck has sat for a month and a half or so, but we are getting busy and I need to get it back on the road now. Have had the following trouble codes pop up the last few times I have fired it up (p0673, p0675, p057c, p262b), then (p0673, p0675, p2771). These are all new to the truck.. The p262b is the one I am particularly concerned about. I have tried hooking up the V2 and shutting down each injector one at a time also- which didnt change anything at all.

It is getting to be where I am at a complete loss at this point. It surely seems electrical to me- but what do i know.. The injector balance rates go nuts when I sit and hold the truck at 1200 while it misfires (tried to attach video but couldnt, so there are screen shots of idle balance rates, then holding at 1200). So I figured I would post in here and see what yall think before I just completely say screw it and take it to a shop. Basically the only two thoughts I have left are to completely rip the wiring harness's off the engine to get a thorough inspection of them.. Or try a new ECM. I am open to trying anything, I just dont want to piss money away on things that wont help at all.

 

[2004LB7]

p262b is ECM power off timer performance. Either the ECM is loosing power before it shuts down or it has an internal fault

Id inspect the harness again. Particularly the power wires that run to the ECM. Some run through the ignition. Double check that. If all os good, them maybe ECM

Balance rates are only valid during idle so I wouldn't put too much stock in the 1200 RPM balance numbers. Fix the p262b first, then work on the remaining codes before condemning the injectors

 

[1FastBrick]

I condensed some of this info for you.​

​

DTC P262B : Control Module Power Off Timer Performance​

Conditions for Setting the DTC​

P0601, P0602, P0606, P060B, P061C, P062F, P2610, P262B​

The ECM detects an internal failure or incomplete programming for greater than 30 s.

P2610, P262B​

The ECM detects an interruption of its permanent battery voltage supply.

Circuit/System Verification​

1. Observe the DTC information with a scan tool. DTC P0601, P0602, P0606, P060B, P061C, P062F, P2610, or P262B should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing​

1. Ignition ON, verify that other DTCs are not set.

2. ⇒X	If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

3. Ignition ON, clear the DTC information with a scan tool.
4. Ignition OFF and all vehicle systems OFF, disconnect the scan tool.
5. Wait at least 2 minutes for the K20 Engine Control Module to power down completely.
6. Reconnect the scan tool.
7. Ignition ON, observe the DTC information with a scan tool.
8. Note: DTC P2610 or P262B can be set with a loss of battery voltage to the K20 Engine Control Module. Disconnecting the battery or an intermittent condition in the battery positive voltage circuit to the K20 Engine Control Module will set DTC P2610 or P262B.
9. If DTC P2610 or P262B failed this ignition, test for B+ at the K20 Engine Control Module connector battery positive voltage circuit terminal X1–67.

10. ⇒X	If not the specified value, test the battery positive voltage circuit for an open/high resistance or a short to ground.

11. Test for less than 2 Ω between ground and the ECM connector ground circuits terminals X2–73 and X3–73.

12. ⇒X	If greater than the specified value, test the ground circuits for an open/high resistance.

13. If all circuits test normal, replace the K20 Engine Control Module.
14. If DTC P2610 or P262B is not set, observe the DTC information with a scan tool.
15. If DTC P0602 is set, program the K20 Engine Control Module. Refer to Control Module References . If DTC P0602 resets, replace the K20 Engine Control Module.
16. If DTC P0601, P0606, P060B, P061C, or P062F failed this ignition, replace the K20 Engine Control Module.

​

P057C​

ECM detects the BPP sensor voltage is less than 0.25 V for 1 s.

For the P0673 and P0675 Glow plug codes here is the diagnostic chart.

Circuit/System Verification​

1. Ignition ON.
2. Using a scan tool observe the following parameters:
   All parameters should closely match each other.
   • Cylinder 1 Glow Plug
   • Cylinder 2 Glow Plug
   • Cylinder 3 Glow Plug
   • Cylinder 4 Glow Plug
   • Cylinder 5 Glow Plug
   • Cylinder 6 Glow Plug
   • Cylinder 7 Glow Plug
   • Cylinder 8 Glow Plug
   • If all parameters do not closely match
     Refer to Circuit/System Testing.
   • If all parameters closely match
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
   • If DTC sets
     Refer to Circuit/System Testing.
   • If DTC does not set
4. All OK.

Circuit/System Testing​

Note: If a glow plug is replaced and the tip is missing or burned off, the cylinder head must be removed and all debris be cleaned out of the cylinder.

1. Ignition ON.
2. Glow plugs not commanded ON, verify that a test lamp does not illuminate between the appropriate Glow Plug Supply Voltage circuit terminal A and ground.
   • If the test lamp illuminates
     Test the glow plug control circuit for a short to voltage. If the circuit tests normal, replace the K34 Glow Plug Control Module.
   • If the test lamp does not illuminate
3. Command the Glow Plugs ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
   • If the test lamp does not turn ON and OFF
     Test the appropriate glow plug control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K34 Glow Plug Control Module.
   • If the test lamp turns ON and OFF
4. Replace the appropriate E12 Glow Plug.

Component Testing​

1. Ignition OFF.
2. Disconnect the harness connector of the appropriate glow plug.
3. Testing for less than 1 Ω between terminal A and ground.
   • If the resistance is more than 1 Ω
     Replace the affected glow plug.
   • If the resistance is less than 1 Ω
4. All OK.