Is it possible to use VCM Scanner to diagnose P0200 on 2004 Silverado?

[Lil'John]

Title kind of states it.

But for more info:
2004 Silverado LQ4 swapped into a Land Cruiser
Getting P0200 engine code
I have verified +12V at all injectors.
I verified continuity from injector to PCM a while ago but will be doing so again.

Is there some of the live information in the VCM Scanner that can help diagnose which bank or specific injector is having a problem?

[vettemakesemwet]

Use each cylinder misfire data to see if any are in fact misfiring. Log BOTH current and history misfires. If misfires logged on a certain cylinder, focus there, if no logged misfires test each injector and circuit. Do you have a noid light? If so, test each injector at the connector and verify each one is as bright as the rest. If not, then use a halogen bulb to test the circuits on specific or each injector. You can read B+ voltage on a wire that is holding on by a couple strands but it will not carry the full load, just the same as you can read continuity but not have enough load carrying capacity. Bulb may light up, but will be dim on the suspect circuit.

Per the service manual, there are 3 possible issues: Wiring(INCLUDES BAD CONNECTIONS), injector itself, or PCM. Each fuel injector is supposed to have 11-14ohms, with no more than 3ohm difference between them. 1 bad injector resistance wise could still fire good enough to not set a misfire, but PCM detects circuit issue. Did you swap in the underhood fuse box from the truck or make your own? Each bank is supposed to have its own supply from a separate fuse, could be if all set on one fused circuit it could throw off the resistance to the PCM but not actually have an issue.

[Lil'John]

vettemakesemwet, thank you for the information and ideas.

I should have a noid light tomorrow.

I'm fairly certain that the power wires are in good shape. I reworked a stock harness and it was running previously. I changed the 'grouping' of the injectors recently that goes to the fusebox.

Is there an easy method to verify good or sufficient grounding of the PCM? This was the other adjustment recently.

[vettemakesemwet]

Is the engine actually misfiring?

If you adjusted a ground, and now you have a problem, revisit what you "adjusted". lol. High resistance to a ground is bad, even more so in a PCM ground. The PCM grounds alot of stuffs to control what makes an engine run.

Ohms with a meter, then load test is my wire checking M.O.

Load test with halogen bulb usually reveals a weak circuit. Noid light is a small load(light) that is best for showing a control of an output(inj, coil, etc). Both great ways to test.

For multimeter testing: Disconnect battery. Disconnect the PCM completely. Find the ground wires on the PCM connector(s). Meter set to ohms, one lead on battery negative, other lead to probe the grounds on the PCM connector. DO NOT FORCE METER LEADS INTO PCM CONNECTORS! lol, this messes stuff up real bad, repairs are tedious. 0.5ohms is perfectly fine. Anything over 1ohm is suspect to me

For load test: Disconnect the PCM completely. Find the ground wires on the PCM connector(s), hook one wire of halogen to B+, connect other wire to ground(s) on PCM connector(s). DO NOT FORCE METER LEADS/PROBES INTO PCM CONNECTORS! lol, this messes stuff up real bad, repairs are tedious.

As a whole, make sure body is grounded to frame, body to engine, engine to frame, battery to frame and engine, and any harness grounds to a good ground on the engine, frame, or as needed. Clean grounds are paramount. Bare metal to wire lug is best, paint OVER connected ground, not ground wire lug on top of paint. Redundant grounds hurt nothing. These systems are ground sensitive.

In short, wiring diagrams, connector pin-outs, a multimeter, and a halogen light bulb with some wires are your best friends when chasing electrical issues.

The above testing with scanner data should get you pointed in the right direction. Hope this helps.

[Lil'John]

Sadly, the noid light set I got wasn't worth a damn. Ten different fittings none of which fit the stock fuel injection electric plug. Even with partial trying to fit one of them in, every injector showed weak spark if I could even see it. I'm assuming it should be naked to visible eye.

This is junk set: https://www.amazon.com/gp/product/B07QCD5CK8

Is there a better kit to consider?

I double checked the wiring from injector to PCM just to be 100% certain. I also checked my data versus an untouched harness. All eight wires were correct.

I split the injection/coil power wires back into driver and passenger side hot in run circuits. I wired both directly to the battery. This changed nothing.

I double checked the ground wires to the single ground at the back of the block. They had continuity. I'll check ohms as recommended once the engine cools down.

I then ran a 14 gauge wire from the LS engine harness ground at the back of the engine directly to the battery. Again, no difference in running.

According to VCM, O2 b1 and O2 b2 are running extremely rich at 850mV to 900mv. I can go to the tailpipe and smell how bad.

According to VCM, on my latest ~2 mile run, cylinder 3 had 58 misfires, #1 had 16, #7 had 8, and #5 had 1. #2 also had 6 and #6 had 1. This kind of tells me that something on the driverside(US) is having an issue.

[Lil'John]

Issue found and not sure if it is one of those "first things to try" type solutions. I swapped a different PCM with the same tune in and I'll call it minimal issues. I think it still needs an additional round of tuning but it is nice to not have the loss of power.

Still interested in what would be considered a good noid light set that will work with stock 2004 Silverado fuel injector plugs.

[vettemakesemwet]

I bought a matco kit a long time ago. Made a load test bulb setup that can double as a noid light. Use both when I am doing any electrical/engine controls diag in a harness along with a fluke meter. Per the pic, the one 3rd from the left top row should be the one. Pic distorts pin sizes a bit, and if this is a cheap knock off of a knock off, then it may not be to spec. You got it connected in any event.

Dim light, but still a flash is what you are after, it doesn't have to be the brightest bulb in the tanning bed, lol. If all are same dim light flash, ithen all injector drivers seem to be in working order along with power source, not to mention your testing of the harness. Ohm the injectors too, don't have spec in front of me but think I remember it being in the 11-14ohm range.

Minimal issues being still have misfires and P0200? I'm looking for different issues, not same ones. Would lend more credit to the bad PCM theory.

Firing order is 18726543. Cylinder #1 would be sympathy misfires as it fires directly after #3. The rest are some minor random thing, need to figure out why #1 is missing at times, provided it still is with the better PCM in it. The others may be a fueling response to #3 misfires.

Let me know how it goes from here.