A Chevy Colorado with GM’s 2.8-liter Duramax diesel kept shaking itself nearly to a stall, dropping two cylinders at a time before the engine shut down. The cause turned out to cost almost nothing in parts: a wire harness that had spent a long time rubbing on an air-conditioning line.
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The case surfaced on Nov. 7 through a repair video from Dave’s Auto Center, a shop that took in the pickup after the owner drove it over from Arizona. Two other shops had already looked at the truck and had done the obvious thing, swapping the injector fuse that kept blowing. The fuse was never the problem, and each replacement bought only a short reprieve.
A fuse that blew only when the truck moved
According to Autoblog’s account of the video, the fault was intermittent, which is the worst kind for a diagnostic bay. The injector fuse would open, the Colorado would lose two cylinders, shake hard and eventually quit. Parked and idling, the truck behaved. The technician, identified only as DQ, worked from wiring diagrams, measured injector resistance and watched amperage during test drives without catching the fault on demand.
What finally broke the case was physical. Moving the harness near the firewall made the injector fuse blow immediately, which pointed the search away from the injectors themselves and toward the copper feeding them. A fault that appears only when wires flex is a classic chafe signature, and it explains why bench measurements of the injectors looked healthy.
Two damaged wires behind the firewall
With the harness exposed, DQ found it had been rubbing against the low-pressure AC line for a long time, wearing through the insulation on two wires. One served the injectors. The other carried the fan clutch signal. When bare copper touched the metal line, the injector circuit shorted, the fuse opened, and the engine dropped half its cylinders, since this Duramax is an inline four.
The repair was modest. DQ repaired the two wires, reinforced the harness and added protection at the contact point, all without pulling the cab. Afterward he test drove the truck and wiggle-tested the harness again, and no fuses blew. The shop’s cost was not stated in the coverage, and the model year and mileage were not given either, so the story is best read as a single documented case rather than a defect rate.
What GM has said about 2.8-liter harness chafing
The failure is not unknown to the manufacturer. A GM service bulletin posted on GM TechLink in November 2020 covers some 2016-2021 Chevrolet Colorado and GMC Canyon trucks with the 2.8-liter diesel, listed under engine code LWN. It says harness chafing can produce a no-start or misfire, plus symptoms as varied as warm air from the AC, a jumping oil pressure gauge, repeated diesel exhaust fluid messages and a pile of warning lamps.
The bulletin tells technicians to finish the normal diagnostics first and then inspect the engine harness and connectors at specific points. The AC compressor, lines and clutch head the list, followed by the serpentine belt area, the rear of the engine near the exhaust heat shield, the bell housing, coolant pipe clamp tabs, the brake fluid level switch, the transfer case encoder motor and the turbocharger vane actuator. Its remedy is to repair the wiring and reroute the harness. It names an open fuse on the AC side as one possible outcome, close to what the Arizona truck showed.
A small diesel with a crowded engine bay
The engine at the center of this is GM’s global four-cylinder turbo-diesel. GM’s powertrain page for the 2.8-liter describes a 2,776 cc inline four built in Thailand, rated at 181 horsepower and 369 pound-feet of torque in the Colorado, with a variable-geometry turbocharger, common-rail direct injection and a balance shaft. Autoblog’s 2015 launch coverage and Equipment World’s rundown of the engine both put the diesel in the Colorado and Canyon crew cabs at a $3,730 premium over the V6.
That packaging matters here. Diesel emissions hardware, a fan clutch, an AC compressor and a turbo actuator all send wires through the same cramped corridor beside the firewall, and every one of those circuits has a fuse and a connector to chase. A harness that sits a few millimeters from a vibrating metal line will eventually lose its insulation, which is why GM’s bulletin reads like a map of contact points.
For owners, the practical lesson from Dave’s Auto Center is about sequence. A fuse that blows twice means something is drawing current it should not, and swapping it again only resets the clock. Asking a shop to flex and inspect the harness near the AC lines and firewall before replacing injectors or modules is a cheap first step, and the bulletin supports it. What remains unknown is how many trucks carry a similar rub point, a number neither GM’s notice nor the shop’s video supplies.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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