P0302
Cylinder 1 Misfire Detected
Powertrain Ignition System Cylinder misfire 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

Cylinder 1 isn't firing properly, causing incomplete combustion—like one cylinder in your engine is misfiring while the others work fine. This disrupts smooth engine operation and increases emissions.

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Symptoms You May Notice
3 known symptoms for this code
Engine hesitation or stumbling under acceleration
Rough idle with noticeable vibration
Check Engine Light illuminated
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors crankshaft speed variation between cylinder firings using the crankshaft position sensor. When cylinder 1 fires, the engine accelerates slightly; if that acceleration is missing or delayed, the ECU detects a misfire. The system counts misfire events over a drive cycle and triggers a fault when thresholds are exceeded.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Crankshaft acceleration (Cyl 1) Expected RPM rise within 10ms of spark event Insufficient or delayed RPM rise detected across multiple combustion cycles
Misfire count per 1000 revolutions 0-2 misfires acceptable ≥3 misfires triggers P0302
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Spark plug (cylinder 1)
Remove and inspect for wear, carbon buildup, or incorrect gap; replace if worn.
2
Ignition coil pack (cylinder 1)
Test for continuity and proper voltage output; swap with another coil to confirm failure.
3
Fuel injector (cylinder 1)
Check for clogs or weak spray pattern; clean or replace if fuel delivery is compromised.