asilverblazer

...ride HEIGHT side to side... \/ \/ \/

The actual measurement "Z-Trim Height", if I recall correctly, is taken from the bottom of the lower ball joint stud, vertically to the center line of the lower control arm rear mounting bolt. An image search would describe this better. If you do adjust the torsion bar to alter this height, the toe amount in alignment is where the most difference is seen. As a side note, adjusting the bolts does not really alter the "force" on the torsion bar and it doesn't alter the spring rate either. All it does is change the relative rotation/position of the bar, this change also 'rotates' the lower control arm the same amount. This raises or lower the ride height. If you adjust it so much that you are against the bump stops then it can begin to pre-load the torsion bar and increase spring rate.

I think you are closing in on it. With these latest results the failing amount of injectors sounds more plausible (#2 might be the source of the trouble codes and drivability issues). I don't think either bank is actually over fueling at this point, meaning that neither bank is getting too much fuel in the cylinders. One bank might be trimming more than the other, but I wouldn't worry about that until it manifests as a problem. ...I suppose one could read a little more into it and look for some correlation between the bank with more trim to the bank with greater average fuel pressure drop... I don't think I would read too much into the average pressure drop across the banks either nor the pressure gauge location. I also wouldn't doubt the test results of the scan tool. If you can repeat the test and get similar pressure drops per cylinder compared to a previous test, I'd trust the readings.

No need to be concerned unless there is a significant difference in ride ride side to side on the front.

I don't think there is a reason to associate a miss firing cylinder #2 to a pass or fail of its injector on the balance test. All the injectors on the bank have to spray the same amount of fuel for the same pulse width. The computer sends a pulse width signal to the all the injectors and expects that each sprays the same specific amount of fuel. Then it uses the O2 sensor data to adjust the fuel trim of that bank to correct the air fuel ratio of that bank, by altering the pulse width signal to all the injectors on that bank. If one injector is out of balance to the others on that bank (whether its good or bad) it will miss fire because it has been leaned out beyond the other injectors. In other words 4 'bad' injectors that fail the injector balance test could still operate fine with no miss fires so long as the PCM can trim the fuel to bring them into proper air fuel ratio via pulse width modulation. If those 4 bad injectors get so bad that pulse width modulation is outside of specification or long term fuel trim is too high/low a code would set to that effect. If you have to get into it anyways, I'd put all the OEM injectors back in to get a baseline.

I'm a little inclined to suggest drive the hell out of it for a bit, let the PCM have some time to read sensors and adjust things. Lots of parts have been changed potentially 'surprising' the PCM with new readings that it hasn't fully adjusted to. Drive it an hour in varying conditions, then check the miss fire counts and long term fuel trims. If after doing so, like above, you have what seems to be an obvious fault on cylinder 2. Put one of the other injectors on it and repeat. Since the MIL isn't flashing the problem isn't TOO bad... I would be concerned about killing the catalytic convertors with a significant miss fire over fueling.

Maybe unhook the negative terminal for a bit the reconnect it. Ignition switch has to be in the run position to get codes. This could indicate an issue still with the switch if you can't get codes.

Did the original injectors ever get tested? Presumably somewhere among the 16(?) injectors you have on hand you could compile 8 that pass testing. I would prefer to test parts than buying (more) new ones, but that is your prerogative.

Now the only code is P0300? Is the MIL flashing? What do the miss fire counts look like? (Cylinder 2 looks lean, fuel trims must be leaning that bank out so much that it is miss firing the leanest of the injectors - this is probably happening on both banks to an extent) 5 Injectors fail the balance test... was it the same 5 injectors as before? Despite what has been done, and no other obvious faults, to me it keeps looking like the injectors are still a problem - which seems unlikely that you would get this many that are bad. If the injectors on one bank are not equal or balanced, then the fuel trims will cause one cylinder to be richer/leaner than the others on that bank. Maybe try swapping injectors 3 and 4 so that bank 1 (cylinders 1, 3, 5 and 7) are all failed or 'bad' injectors and bank 2 has mostly passed 'good' injectors (cylinders 2, 4 and 8 except for cylinder 6). Then I would expect the miss fire to move to cylinder 6, since it is the out of balance injector on that bank.

A wheel speed sensor causes lighting issues? I doubt it, the service trailer brakes and ABS light, sure.

Truck needs new catalytic converters (P0420, P0430). This should resolve the P2099.

Did you work through those? What did you find?

Have you checked all fuses? Is there no power at the OBDII port?

I would suspect any number of wiring faults before a bad BCM.

Check the cables for corrosion. Use jumper cables to bypass them if necessary to test. Run a jumper cable from battery positive to starter terminal. Run a jumper cable from engine to battery ground.

If the keys are original a theft issue would be less likely than a bad switch. If it is the start position of the switch, you should be able to put it the run position and jump the starter and the truck will run. How have you ruled out the starter solenoid? A random other failure following a starter replacement would be awfully coincidental.

Why did it sit for a month? Why are you adding fluid? Is the fluid level low? It should only be checked when hot. Was it working when it sat for a month? If it is a transfer case issue, the transmission isn't going to work and vice-versa. Same for the rear differential... So what is the story that you're thinking there is problem with major components just by sitting? Dooping someone by swapping out a major drivetrain component - and putting a faulty one back in its place - is... unusual.

Short answer yes. I wouldn't worry too much about being 'stuck' in open loop. That should correct itself when the problem is corrected. In open loop it is ignoring the O2 sensors, the only problem immune to that would be an ignition problem, cylinder 5. Once that is resolved (cylinder 5 miss fire), you have on hand an assortment of O2 sensors to try on bank 2 to see what is happening.

You must be exhausted... sigh. Current codes are still P0300, P219A, P050D, P0171 and P0174? It looks like that up until January 2024 at around 110k miles all engine misses were ignition related. All 03xxx codes call for a thorough ignition diagnosis prior to moving to a fueling problem. If the ignition problem remains unchecked the fuel injectors are still working as intended and by virtue of the poor ignition sending unburnt fuel into the exhaust. likely fouling O2 sensors and also indicating rich condition that the PCM would try to correct by leaning that bank out. This would be seen in fuel trims. Now the P219A code starts appearing, a fuel trim code. This led to O2 sensor replacement that corrected it, likely because of the sooty/rich unburnt fuel from poor ignition fouling the sensor. Notably the P0300 and P219A codes remain. Meaning the original problem has not been corrected. In mid march the injectors are replaced based on a recommendation from a GM tech. The problem remained and has up to today. It seems to me that after reviewing all this, a complete diagnostic of the ignition system has not been done. The truck has new(ish) plugs in it that might be fouled from poor combustion, I would pull and clean them. The wires are new, I would caution that like sensors 'house' brand are not recommended (I personally have had a brand new set with a bad wire in it). Lastly, the coils are also new but one could still be bad (#5). I'm inclined to think that an ignition (still possibly fuel) problem exists on cylinder 5, the spikes in O2 readings from that bank correspond to those miss fires. Swap 3 and 5 coil, then wire, then plug to see if the miss fires from 5 move to cylinder 3. I think first get the obvious miss fire corrected, then figure out bank 2.

There was another thorough discussion of this problem... I'd start with a search and see if you can find that thread that was full of suggestions and solutions as I recall.

Good! My memory is fuzzy but the upstream sensor should fluctuate as each pulse of cylinder gas passes over it. A steady reading could indicate a sensor fault, or it could be so sooted it up that it can't read. Either case will cause the PCM to not be able to correct the air fuel ratio. If the sensor isn't reading and it doesn't detect anything then it could be assuming incorrectly and leaning out the bank unnecessarily. I would not rule out a thorough diagnosis of the O2 sensor circuit. Can you re-summarize what parts you have replaced when? I might be going in circles not understanding what you have done already, somethings may already be corrected. Have you cleared codes prior to new tests?

Probably wouldn't hurt to take a step back and look everything over, is all the wiring good, sensors plugged in completely, no corrosion, etc. There has been a lot of work performed on the intake of the engine, something may have gotten damaged. Inspect for vacuum leaks, intake leaks, oil cap on and tight, dip stick fully seated. The IAT is a pretty simple sensor, and the code is very specific. I bet this code doesn't repeat. The presence of P0300 and P0219A is odd because P0219A should not set in the presence of P0300. P0219A is sensitive to O2 sensor and intake conditions. P050D is another fueling specific problem. P0171 and 174 should not be present with the P0300 either but indicate lean conditions. Short version... the PCM is having trouble correcting the air fuel ratio either it isn't getting an accurate idea of the amount of air or it isn't able to deliver the correct amount of fuel.

See this link... https://www.gmupfitter.com/wp-content/uploads/2021/05/2004_MD_CSeries.pdf

I would disassemble the IPC and look for shorts. Some careful probing with a multimeter ought to be able to track it down. I suspect the C1 connector has an 'always on' circuit in it that is back feeding the MIL circuit and thus throwing the code. I don't have a diagram to refer to to try narrowing it down further.

Bank 2, with the black O2 sensor also failed all all the injectors on the balance test - over fueling bank 2. I don't think the issue 'moved'. I don't suspect a valvetrain issue. The changes you made could have cleaned up some of the miss firing problem on cylinder 2. Cylinder 5 is definitely a problem. "Some" amount of miss fires are acceptable and normal. It seems that the other 7 cylinders might be with in that tolerance. If you made all the changes to the air intake above then recorded this test I would unplug the battery for a while to reset then retest again. The intake changes may have 'surprised' the PCM. Since you know the LTFT trims... I would definitely repeat the injector balance test. What injector test are you using? Fuel Injector Balance Test with Active Fuel Injector Tester or Fuel Injector Balance Test with Scan Tool This many failed injectors is also suspect, are they from a dealer or could they be from 'somewhere' else that might be counterfeit? If the bank of cylinders fails again, I would look at fuel rails and lines. Also, note that in the above excessive fuel pressure could cause some issues. Is the fuel rail pressure remaining in tolerance?