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2020 S60 T5 Rough Idle and CEL - P0301 Code

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Mike T. · rep 0 · May 24, 2:53 PM · 1 replies · solved · Question

Vehicle: 2020 Volvo S60 T5 Momentum

Hey everyone,

My 2020 Volvo S60 T5 Momentum has developed a rough idle lately, especially when cold. It feels like a slight stumble and sometimes the engine shakes a bit more than usual.

The Check Engine Light came on yesterday. I used my OBD-II scanner and pulled a P0301 code, which indicates a misfire on cylinder 1.

Has anyone experienced this with their S60? What are the common culprits for a P0301 on these engines? I'm trying to figure out if it's something I can tackle myself or if I need to take it to the dealership. Any advice on troubleshooting steps would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 2:53 PM

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ClearTheCode admin answer:

A P0301 code on your 2020 Volvo S60 T5 Momentum indicates a misfire detected in cylinder 1. This is a common diagnostic trouble code (DTC) that can stem from several issues.

Here are the typical causes and troubleshooting steps:

  1. Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. Even on a 2020 model, a faulty plug can occur.
  2. Ignition Coil: A failing ignition coil for cylinder 1 would prevent proper spark. These can degrade over time or fail prematurely.
  3. Fuel Injector: A clogged or faulty fuel injector for cylinder 1 could lead to an improper fuel-air mixture, causing a misfire.
  4. Vacuum Leaks: Less common for a single cylinder misfire, but a significant vacuum leak near cylinder 1 could affect its air-fuel ratio.
  5. Compression Issues: In more severe cases, low compression in cylinder 1 (due to valve issues, piston rings, or head gasket) can cause a misfire. This is less likely on a newer vehicle but shouldn't be entirely ruled out.

Troubleshooting Steps:

  • Swap Components: A good diagnostic step is to swap the ignition coil from cylinder 1 to another cylinder (e.g., cylinder 2). Clear the code and drive the car. If the misfire moves to cylinder 2 (P0302), you've identified a faulty coil. You can do a similar swap with spark plugs if they are easily accessible.
  • Inspect Spark Plug: Remove the spark plug from cylinder 1 and visually inspect it for signs of fouling, damage, or improper gap.
  • Fuel System Check: If coils and plugs check out, consider having the fuel injector for cylinder 1 tested or replaced.

When to See a Shop:

If you've tried swapping plugs and coils without success, or if you're not comfortable performing these diagnostics yourself, it's best to take your S60 to a qualified Volvo specialist or dealership. They have advanced diagnostic tools (VIDA/DICE) that can perform more in-depth tests, such as fuel pressure checks, injector pulse tests, and compression tests, to accurately pinpoint the root cause of the P0301 code and rough idle. Continuing to drive with a persistent misfire can potentially damage the catalytic converter over time.

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