GMC Canyon owner chased sensor codes, then dealer said a new engine would cost what the truck did

A GMC Canyon owner went to a dealership for answers about sensor codes and a no-start issue, only to leave with an estimate of about $25,000 for a full engine replacement.

That estimate was especially frustrating because it was roughly the same amount the owner had originally paid for the 2016 truck.

Here's what to know

According to Guessing Headlights, the owner detailed the situation in a post on Reddit's r/MechanicAdvice, saying the 2016 GMC Canyon's 3.6-liter engine had triggered several trouble codes, including camshaft position sensor faults. 

The owner wrote that they were "Quoted for an engine replacement and looking for second opinion — How to go about this?"

Before going to the dealership, they said they had tried to diagnose the issue themselves because they suspected a wiring-related problem. Once technicians inspected the truck, they reportedly found the timing chain was still intact.

The more conclusive tests were far less encouraging. A leakdown test showed 95% leakage in cylinders one and five, with air reportedly escaping through the exhaust valves, while compression readings came back at 30 pounds per square inch for cylinder one, 100 psi for cylinder three, and zero psi for cylinder five.

Those findings were accompanied by a borescope inspection that technicians said appeared to show possible piston-to-valve contact along with metal debris. Together, the results suggested the engine may have jumped timing internally, which could account for major mechanical damage and the expensive recommendation.

More background

The quote was even harder for the owner to accept because they said the dealership had already damaged their trust. According to the post, earlier disputes involved work performed without approval and unresolved purchase incentives that had already cost them thousands of dollars.

The owner also said the situation came at a particularly difficult time because they were getting ready to move to a city about eight hours away, making it harder to coordinate multiple inspections.

Even with the truck's age and mileage, the owner said they would prefer to repair the Canyon rather than replace it with another vehicle.

Commenters agreed the compression and leakdown figures suggested serious internal engine damage. Still, they questioned whether a dealership estimate that nearly equaled the truck's original purchase price should be treated as the only viable fix.

What can be done?

The owner said they planned to ask for the shop's diagnostic records so another repair facility could review the compression, leakdown, and borescope findings before approving any expensive work.

Commenters encouraged the owner to avoid a dealership replacement and instead compare independent options, including used or remanufactured engines. One commenter estimated that the engine itself might cost about $5,000 and include a five-year, 50,000-mile parts warranty, though installation would be extra and any future swap under warranty would still leave labor uncovered.

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