The various modules communicate with the PCM on a "bus" system, and if a module stops communicating, the PCM flags a communication error. Loss of communication causes problems itself, and a module that's gone offline can cause all sorts of other problems - like disabling the traction control, or signaling the PCM to go into limp mode. If it does it all the time it can be reasonably easy to diagnose, but if does it rarely it can be pretty tricky, to the point of relying on a lucky guess or two. The problem at dealerships is the guys are paid on flat rate and nobody makes any money on this sort of problem, so nobody really wants to deal with it. I'd be inclined to lean towards threatening lawsuit or demanding a loaner car and refusing to take the truck until its fixed. In that case, the service department would be motivated to get someone to do the work, and free up some "internal" funds to cover the time spent.
Probably the IAC valve, but cleaning the throttle body is basic maintenance as well. If you pull off the air horn at the throttle body, look and see if the throttle plate and bore are full of gunk. They usually are, and you can take a clean rag and some brake clean or carb clean and wipe it down until it looks new. That solves all kinds of idling problems, and I'd always give it a try before replacing parts or paying for diagnostics.
You probably have disc all the way around, and probably the inspections have been limited to looking at the calipers and pads. On the rear the e-brake works like a drum brake, inside the rotor. You have to take the rear calipers and rotors off to inspect the e-brake mechanism. The e-brakes on those do fail regularly - there is a clip on each side that holds the shoe assembly in place, and the clip tends to break. Then you have a brake dragging and catching on occasion, and wearing out the inside of the rotor as well as the shoes themselves. Its worth taking apart to have a look, and its a "first check" on any of those rigs with a low e-brake pedal complaint.
Ball joints don't cause that, though if they're loose they should be replaced anyway. Typically its either caster is too high, a tire is out of round (see if rotating them changes anything) or more likely you just need a steering stabilzer.
I'd just replace the axle, its pretty quick and easy. The universal boots are crap, and the oe silicon boots are a real pain to get on; if you don't get the clamp just right, it'll come back apart soon enough. I've put on a bunch of axles of various brands and never had a comeback on a pickup, but if price were reasonably close I'd probably go with an OE model, or at least with a new rather than remanufactured. There's no reason to replace the hub, unless it has play or bearing noise, and you usually don't have to remove it, or the caliper or brakes, to pull the axle.
Replace "Tech" with Service Writer or Salesman and that's about right most of the time. I don't think most sales guys have much of an idea about what an alignment is or does, and I know plenty of 4-wheel alignments get sold on rigs that don't have any adjustments on the rear. I was more comfortable at my old shop where I knew the customers, asked them what the car was in for, sold the work, did the work, and delivered it back with an explanation of what I had to do and how it went. Now I'm at a dealership back in the bays, and I just try do flawless work regardless. Miscommunication is a regular thing, but the best way to avoid problems is to do good work. It pays much better and the equipment is better, and we're up to our ears in work most of the time, but I can understand how much harder it is to get satisfying service, or work done that feels like a good value.
Depends on how picky you want to be. If I test drive one and the steering wheel is cocked one way or another, I'll probably align it, because I know I can get it perfect, and it will be a noticeable difference (assuming the customer is paying attention). If I set one up for readings and its not at the preferred setting for toe, give or take five hundredths of a degree or so, I'll probably align it. A tenth of a degree toe will show noticeable wear after 10k miles or so, though the "green" range is often wider than that. Technically, allowing for the ranges, a lot of rigs can be in alignment, "in the green", but still show tire wear and drive squirrelly. And if you're looking at ride height as a part of the alignment, most GM trucks with torsion bars can stand improvement. So - probably about right with the 95% being either out of alignment or "could be better". But it doesn't always matter much. If you don't put a lot of miles on the rig you can put it off for a couple of years without big issues. Plenty of people have to replace their tires for age before the tread wears out. On the other hand, if you put a lot of miles in its a god idea to have the alignment spot-on.
The first part of the alignment is setting the front ride height, which directly affects the rear ride height. I wouldn't worry about the rear until you've done the front. (If one torsion bar is cranked up, it will drop the opposite rear corner).
I haven't seen that problem from a worn out torsion bar, but it is possible. A worn out spring can cause that, though its not very common at all. In any case, I would start with an alignment, and make sure they begin by setting the ride height. If that can't be set, then the torsion bars would definitely be suspect. If the ride height comes out ok, then there are plenty of other front end parts that wear out on those - idler and pitman arm being the obvious ones. The steering gearboxes on those also loosen up predictably, though its not easy to find someone able to set that up right (I taught myself, having worked in 6 different shops without a tech willing to touch the gearbox except to replace it). If nothing bad is found and it can be aligned its worth doing, and see how it drives from there.
We use a machine to flush the system. Usually you disconnect the upper hose at the radiator and install a bridging hose that has connections for a flush and a return line. Warm up the engine until the t-stat opens, close the bridge, push new coolant into the radiator side, and the old fluid is forced up and out through the thermostat. Pretty simple. I'd also say - pretty unnecessary in many cases, as you could just drain the system by pulling the lower hose, but its reasonably fast and clean with the machine, and no air is introduced into the cooling system (which can be a problem to purge on some vehicles).
If its a newish GM truck there are three or four different clip systems, but at least two of them use clips that are held in place between the pads by a bit that pushes up into the cast iron pad holder. They have to be pushed up into place so don't contact the rotor. Its easy enough if one is rubbing on the rotor to see where its rubbing, and then push it into place so it doesn't. If you've messed up the new clips there's nothing wrong with re-using an old clip; its a good idea to use a little silicon lube on the ears of the pad backing plates (the metal-to-metal contact points), either way.
For the left rear to be not braking currently, but braking enough to wear out the shoes at some other point - I'd say the wheel cylinder is most likely. When a cylinder starts to freeze up it will still apply, but it won't back off under spring tension - so your brakes drag on that wheel. When it fully seizes up, then the shoes won't apply at all. Its easy to check - open the bleeder at that corner while someone presses the brake pedal. If fluid squirts out, then its all good up to the cylinder. With the drum off use a screwdriver or prybar to shift the top of the shoes from side to side. They bear on the wheel cylinder pistons, and if they won't budge then the cylinder is frozen.
Yup. The surface that the seal rides on is the machined part of the axle shaft. If that's worn or damaged at all, it won't seal, so replacing the shaft is the obvious second step. I've never had to replace one on a front diff, but I've never had a repeated comeback with that problem. Inside the housing is the bearing that supports the axle shaft; if that's worn it allows the shaft too much play, and again the seal keeps leaking. I'd probably replace the seal, axle shaft and bearing together - they pretty much work as a set. I've had to do that more than once on rear axles, where a quick seal replacement has come back leaking again.
Ford isn't any better - toe out on every new solid axle one I've looked at. I think they have a machine that spins the adjuster to the correct toe, then another machine that runs the clamp bolts down - which brings the heavy cross bar up and changes the toe. Dodge isn't much better either - every new 2500 and 3500 has crooked steering wheel. And don't get me started on Subarus...one of the few cars, with their new electronic steering assist, that just drives screwy (usually) and there's not a darn thing I've found I can do about it.
The last aftermarket pump I put it a GM wouldn't bleed out or build pressure. I had to fill the high pressure line and force the fluid past the pressure valve with air, after which it worked fine - for a few days, when it came back with no PS assist again. That's the sort of thing that makes for an aggravating day. I put a better pump in it and that worked right out of the box. I'd suspect the pump.
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