Meaning

The ECU has detected misfire events isolated to a single cylinder but cannot conclusively identify which cylinder is responsible. This code is set when the misfire is intermittent, migrates between cylinders, or when the crankshaft position sensor signal does not allow unambiguous localisation. It frequently appears alongside other P030X codes.

Common causes

• Rotating misfire caused by low common-rail fuel pressure affecting cylinders in sequence
• Crankshaft/camshaft correlation out of tolerance preventing precise cylinder identification
• Intermittent fault on a spark plug or ignition coil manifesting across different cylinders
• Compression loss on multiple adjacent cylinders (compromised head gasket)
• Distorted or noisy CKP sensor signal degrading misfire detection resolution

Symptoms

• Check Engine light on, possibly flashing during misfire episodes
• Vibration or rough running felt in the cabin
• Variable, inconsistent power loss
• Shuddering or instability at idle or under partial load
• Presence of additional P030X codes or absence of any cylinder-specific code

Severity

What to do

1. Perform a full scan for associated P030X codes and freeze-frame data
2. Monitor per-cylinder misfire counters in real time with a scan tool to identify any pattern
3. Check fuel pressure and injector flow rate, especially on common-rail engines
4. Inspect the CKP sensor signal and CKP/CMP correlation with an oscilloscope
5. Carry out a compression test and leak-down test on all cylinders to rule out mechanical causes

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