carkhz316

Need to scan for system-wide DTCs. My bet is a "Loss of Comms" or "Communication Bus [x] off" , but finding out what is taking which network down will be the bigger challenge. Scan tool Topology can help, but just having a good wiring diagram with data line schematics can tell you what modules talk to one another.

Gosh is this certainly true. I've wasted a bit of time with aftermarket sensors causing repeat and new o2-related DTCs. I've had multiple Denso sensors cause faults. The worst part is some of the GM sensors are made by Denso, but I guess the quality control varies between their own and contract parts.

Are you meaning for the parking sensor/ dome light issue or in general? If the latter, I've replaced dozens of BCMs across GMT 800 through K2 trucks for a variety of concerns and failures.

No you're not doing anything wrong. It continues to warm up even while idling, which expands the fluid and continues to be a steady trickle. As long as its not gushing or glugging out, its fine. If you want to confirm proper fluid level: - top it off and run it to minimum check temp, cycle through the gears down to [1] pausing in each position for a couple seconds and ending back in PARK. Pull the check bolt and when its a thin line stream stick it back in and call it a day.

The HMI also handles switching of the rear camera input/ output, so the fact that the backup camera works on demand generally rules out the HMI as well. If the HMI fails, you'll still have sound coming from the radio, but the infotainment will be blank or unresponsive. Typically, stations and volume can be controlled from the instrument cluster if that happens. The radio, amp, HMI, CD player, and instrument cluster are on their own dedicated communication bus known as the Media Oriented Systems Transport, or MOST bus. It is fairly easy to diagnose with the proper tooling. GDS2 and some aftermarket scan tools will outline which 'node' or module (of the aforementioned components) are not working properly and help to isolate the defective module or circuit portion. The dealer should have been able to find this out without too much effort.

I don't think I've seen a police car WITHOUT holes [strobes] in the handlamp like that; at least up until recent with full LED lamp assemblies that can perform strobe-like functions.

You're likely on the right track. See below:

Need to enhance. We can't see the individual RGB chipsets yet.

I end up using GDS2 for certain GM vehicle functions, including Brake System Plunger Motor Position Sensor Learn and the Hydraulic Circuit Installation Verification when doing some of the brake repairs on Tx trucks and SUVs. Some scan tools won't run the routine(s) properly. I like to flush the brake fluid on my vehicles periodically, but unless you absolutely need to perform an automated bleed to rid the EBCM of fluid, then I would recommend a manual or pressurized flush/ exchange and call it a day. Do this with the battery disconnected and you won't have to run the aforementioned routines.

It'll be fine. I'm in MN too and most of these trucks with that age and mileage are in that condition. I wouldn't sweat it too much.

TL;DR You're likely fine. The mountain climbing makes it work harder so it ran a bit warmer. Anything under 200* is fine.

Your code reader is either not reading body codes, or its not reading the BCM. It won't have anything to do with the transmission. Unless you have an ABS warning or some other fault, I would disregard and instead pursue the transmission issue as a primary focus.

All my previous trucks didn't start to see cooler hose seepage until 10 years/ 150k miles on average. My current truck was dripping at half that. Thats what I'm underwhelmed by. They're actually quite easy to disconnect. Routing them out and back in a bit more work.

I don't know what you're getting at. You mention not knowing much about the transmission and wanting to learn, yet then counter my points despite evidence. The torque converters are the same. There are certain applications of 1-ton trucks and vans utilizing a 6-bolt mounting vs the 3 bolt, but they're otherwise physically the same. Regarding the transmissions themselves: "nearly" identical is a slight exaggeration. They share 'only' 75% of their internal parts https://www.novak-adapt.com/knowledge/transmissions/automatic/6l80.html https://gearstar.com/blog/6l80-vs-6l90-devils-in-the-details/ Key differences of the 6L90 include: A longer case, different output shaft, an additional clutch friction in the clutch packs, and 6-pinion planetaries. Most of the remaining hard parts are the same and interchangeable.

Its not too bad if you're mechanically inclined, but you may as well utilize your warranty if you can. You deserve that privilege when they can't make stupid simple things last anymore.

I mention the 6L80 because they're nearly mechanically identical to the 6L90. They even use the exact same JMBX torque converter. The TCC clutch piston deforms under pressure and causes uneven wear over time. Once the friction lining is worn through on the clutch surface, it then begins grinding metal off the face and sending it with the fluid flow through the oil cooler and back into the transmission. Once the wear sets in, its a cascade affect. This manifests itself in the beginning stages failure as a "shudder" or sometimes torque converter clutch hunting at highway speeds; particularly with high load and low engine speed. The 6L90 does have better shift and TC control strategies because it has to given its design purposes, including towing/ hauling and for performance in the applicable sports cars. Heat exacerbates the issues one sees. 6L90s in particular have lasted much longer historically, because (at least in the trucks) they never utilized a thermal bypass valve like the 6L80 did until the T1X trucks beginning in 2020. For some more reading that goes over the 6L80/ 6L90 issues: https://www.sonnax.com/tech_resources/845-6l80-6l90-transmission-tech-advisory-consider-an-updated-converter-in-your-next-rebuild

The same thing that wrecks the 6L80 generally: A poorly designed torque converter. The TCM control strategy has the TC clutch applying in low gears and to constantly slip so as to insulate the driver from transmission operation. The torque converter itself is very cheaply made and allows the TC clutch piston to deform and exacerbate the slippage causing the clutch to wear out and start churning out metal filings into the rest of the transmission. Valve body issues, such as the AFL valve can start to bind or chatter from dirty fluid, which contributes to the clutch wear issue, as well as the pressure regulator valve in the pump. You can stave off valve wear/ sticking by adopting severe duty maintenance intervals on the trans fluid and filter, such as every 30-40k miles, which sounds extreme, but has been proven to help in the long term.

Its either the engine oil cooler or transmission oil cooler line. Both engine lines and 1 of the trans lines go the right side (as pictured) and the other trans line goes towards the left side (if the gas engine). I can about guarantee its leaking at the crimps. I just had to replace/ repair mine last fall right after warranty expiration (of course). When I had them out, I could spin the hose around on the hard line while it was still crimped. They're just made so cheaply as the hose was also very hard like plastic. I bought new Goodyear oil cooler hose and used crimp-style AC line ferrules to rebuild mine along with a cheap hydraulic crimper. They've been fine since. The dumb thing is that engine oil cooler lines are covered under powertrain warranty, but trans cooler lines are not. But, since you have the CPO b-t-b warranty still, they should be obliged to cover the trans cooler lines as well, though don't be surprised if you're met with the typical bullshit lip service where they tell you that its deemed 'acceptable seepage' and will deny the warranty claim. Then, the day after warranty is expired, suddenly it turns into a danger-critical repair that they need to perform, paid for out of your pocket of course.

Its fairly straightforward. You'll have to lower (not remove) the front diff to get them out and back in.

Seconded.

Is the brake light/ turn signal bulb working on the left side rear? BCM failure is not uncommon for random, trivial concerns as this in the K2 platform for some reason. As mentioned, the rear lamps are directly controlled by the BCM. If there ever is a wiring problem, such as a short to ground, the driver for the rear lights will eventually be destroyed. Why there is no fused protection is beyond me, but it is what it is.

Which one? Front or rear? If rear, and the lamp itself is illuminating properly, then its a failed BCM. I've replaced many for the rear lamp failure in working/ non-working lamp instances. The BCM directly controls the rear brake/ turn combo with no fuse or relay in line.

They're confusing the half tons, which have the integrated service/ parking brake assembly (the actuator engages the disc brake pads) with the HDs that have a separate drum-in-hat style parking brake. Mechanically, its the same as its always been. Its just the foot pedal and cable has been replaced with an electronic actuator like everything else.

If they did indeed voltage drop the entirety of the positive side and the ground side, it honestly doesn't sound excessive. On paper it does, but you have hundreds of amps of current and half a dozen connection points. All that I've measured on healthy trucks have been anywhere from 400mV to 800mV total. I'm betting now that new cables won't change anything. If you're ambitious, you should see if someone can measure the actual current draw of the starter. Typical GM gas V8s are between 200-250 amps while cranking in clear-flood mode (pedal to the floor).

I'm not positive about the bumper harness as I kept my older bumper setup while updating the grille and headlights. The active grille shutters are nearly the same, but have different attachment points for the grille. You don't NEED the newer frame, but if you reuse your older one, a few of the grille clips won't have anything to attach to. It'll still work though.