The L5P kept the same CP4.2 pump that took out the LML, and as the early trucks pass 150,000 km, the failures are arriving on schedule. We replace the pump and injector set at your home.
When GM launched the L5P Duramax in 2017, it fixed a lot of the LML's weak points, but it kept the Bosch CP4.2 high-pressure pump. The failure mode didn't go anywhere: the pump's roller followers depend entirely on diesel fuel for lubrication, and when that film fails, a roller cocks sideways on its cam lobe and machines itself into metal dust.
Early L5P trucks are now aging past 150,000 km, right into the wear window, and the pattern from the LML is repeating. The pump sheds metal at injection pressures north of 2,000 bar, driving debris into the rails and all eight injectors. Symptoms ramp from subtle (longer cranks, a small power drop) to undeniable (multi-cylinder misfires, hard starts, metal in the filter) over a surprisingly short span.
The repair logic is the same hard lesson the LML taught everyone: a new pump alone, fed by contaminated injectors and rails, fails again. The job is the pump and the full injector set together, with the high-pressure circuit cleaned and verified. On a truck this new and this capable, the repair is absolutely worth doing, these trucks cost serious money new, but it has to be done as a system, not a part.
If your GM is doing any of these, this is the likely cause:
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CP4.2 Pump & Injector Set Replacement is a big job and shops quote $10,000–$15,000 for it. The single most valuable thing you can do before committing that is have the diagnosis confirmed independently, $100–$250 flat, at your location, no hoist needed, because a diagnosis isn't the repair. Plenty of cars arrive at that quote and turn out to need the smaller version of the problem.
And the honest scoping condition, up front: once I've seen it, I tell you straight whether it's something I can do at your place. If it needs a hoist, a press or a machine shop, I say so and point you to someone who has one. I don't take a job and figure it out in your driveway. That's the whole deal, and it's why the diagnosis comes first.
What the car is doing plus what you've been quoted. Fares reads his texts between jobs.
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CP4.2 contamination is progressive and one-directional, metal that reaches an injector never leaves on its own. Caught at the first symptoms, rails and lines can sometimes be verified clean and saved; driven to the no-start, the contamination is total and the parts list is maximal. The difference between acting on the first hard start and acting on the tow truck is thousands of dollars of salvageable hardware.
Yes, two days of driveway work on jack stands. Pump, injectors, rails, and the tank-forward cleanout are all field-serviceable with the right tooling, which we bring. No tow, no shop queue, and you can see every old part that comes out.
Eight injectors plus a pump is a genuinely expensive parts list even at our cost, and dealers price those parts at list and stack thirty-plus book hours on top. What we change is the labour math and the transparency: one flat price for the complete, defined job before we touch the truck.
Check your powertrain warranty first, genuinely, if you're inside it, the dealer is the right answer and we'll tell you so. The trucks coming to us are past warranty by age or kilometres, which on a work truck in the GTA happens fast.
Not always, it depends how far the debris travelled, which we verify rather than guess. Lines and rails that inspect clean can stay; injectors can't be saved once exposed because their tolerances are microscopic. We replace what the contamination dictates and show you why.
Send it over for a free second opinion. I'll tell you straight what the job actually involves, and if their quote is fair, I'll tell you that too.
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