Flickering Check Engine Light & Rough Idle on Your Volvo S60 III

First, What a Flickering Check Engine Light Really Means

A steady check engine light says "something's off, but I'll wait." A light that flickers or flashes says something very different — it usually means the engine is misfiring badly enough that unburned fuel is being dumped straight into the catalytic converter. On your Volvo S60 III (the 2019-and-up car on the SPA platform, mostly with the 2.0L Drive-E four-cylinder), that converter is expensive. So treat a flickering CEL as a "get it looked at today" warning, not a "next oil change" warning. The rough idle you're feeling is the other half of the same story: one or more cylinders aren't firing properly, especially at low RPM where the engine has the least momentum to hide it.

The Usual Suspects on a Drive-E S60

Rough idle plus a flashing light almost always points to a misfire. When this combination rolls into the shop, I check these in roughly this order:

• Ignition coils and spark plugs. The most common cause by far. Drive-E coil packs break down under heat, and worn plugs widen the gap and stress them further. A single failing coil gives a distinct shake at idle that smooths out as RPMs rise.
• Fuel injectors and the high-pressure fuel pump. Direct injection means dirty or leaking injectors cause lean misfires. A stumble with a fuel smell points here.
• Vacuum and intake leaks. A cracked intake boot, a leaking manifold gasket, or a torn PCV diaphragm leans out one cylinder or the whole engine.
• Mass airflow (MAF) sensor and throttle body. A dirty MAF or a carboned-up throttle plate gives lumpy idle and hesitation, but usually smooths out once you're moving.
• Compression or valve issues. Less common, but carbon buildup on the intake valves of a direct-injection engine can cause a stubborn misfire on one cylinder.

What to Check First — and How

Please don't start swapping parts. Have the codes pulled with a proper scan tool and look for P0300, P0301, P0302, P0303, or P0304 — the misfire codes. The cylinder number tells you a lot: a single-cylinder misfire points to that coil, plug, or injector, while multiple cylinders point to fuel delivery, air leaks, or a sensor shared across the engine. From there, watch live misfire counters and fuel trims at idle. A misfire that only shows up at idle and clears off-idle is classic for a vacuum leak or a weak coil. Beyond that: a smoke test for leaks, a fuel pressure check, and — if the misfire won't follow a known-good coil — a compression and leak-down test.

Is It Safe to Keep Driving?

Honest answer: no. A flashing or flickering check engine light means raw fuel is hitting the catalytic converter, and that's a danger to your wallet — converters on these cars are not cheap, and repeated misfires can wash cylinder walls and dilute your oil. If the light is flickering and the car is shaking, stop driving as soon as it's safe, then have it towed or drive it straight to a shop at low speed and light load. If the light only flickers briefly under acceleration and the idle is just slightly lumpy, you can limp it in for diagnosis — but don't put it off for weeks. In almost every case, catching this early is the difference between a coil pack and a four-figure repair.

This material is AI-generated and for informational purposes only — it does not replace an in-person diagnosis by a qualified mechanic.