2020-2024 GMC Sierra 2500HD Ignition and Engine Management: What Wears and When to Replace It

The ignition and engine management system on the 2020-2024 Sierra 2500HD is not complicated, but it is easy to spend money in the wrong place on it. This is the version we give people at the counter.

What You Will Notice First

A rough idle that smooths out above 2,000 rpm
A misfire code that follows the coil when you swap it to another cylinder
Fuel economy that drifts down a mile or two per gallon over a few months
A check engine light that flashes under load, which means raw fuel is going into the converter

None of these are emergencies on day one. All of them get more expensive if you sit on them.

The Parts Involved

Spark plugs.
Ignition coils.
Camshaft position sensors.
Crankshaft position sensors.
Oxygen sensors.
MAF sensors.

Why the Factory Part Matters Here

Plug gap, heat range and electrode material are specified per engine, and GM’s Active Fuel Management and Dynamic Fuel Management engines are sensitive to it.
Coil primary resistance affects dwell, and the ECM is calibrated for the factory value.
Oxygen sensor response time is what the fuel trim strategy is built around; slow generic sensors cause driveability problems that never set a clean code.

Service Interval

Iridium plugs on most modern GM engines are a 90,000 to 100,000 mile item. Coils are replaced on failure, not on a schedule.

Ordering Notes

The same nameplate can have three different engines in one model year. VIN is the only reliable way to get the right plug. On the Sierra 2500HD specifically, trim and package content is the thing that trips people up.

Genuine GM parts, dealer priced, shipped from Dallas. our GMC OEM parts catalog has the full catalog, or search for spark plugs.