Cylinder 4 Misfire or Contribution Fault
The P0272 code indicates that the Engine Control Module (ECM) has detected a cylinder power balance fault, specifically that cylinder 4 is not contributing its fair share of power compared to the other cylinders. This is often caused by a misfire due to fuel, ignition, or mechanical issues. The ECM monitors crankshaft acceleration to detect imbalances, and when cylinder 4's contribution falls below a threshold, this code is set.
1. Most Common Causes
- Faulty fuel injector on cylinder 4
- Ignition system issue (spark plug, coil, or wire) on cylinder 4
- Low compression in cylinder 4 (worn rings, valves, or head gasket)
- Vacuum leak affecting cylinder 4
- Engine mechanical problem (e.g., camshaft, timing chain)
2. Symptoms You Will Notice
- Check Engine Light on
- Engine misfire or rough idle
- Reduced power and acceleration
- Poor fuel economy
- Engine vibration at idle
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Perform a cylinder contribution test using a scan tool to confirm cylinder 4 is weak.
Step 3: Inspect spark plug and ignition coil on cylinder 4; swap with another cylinder to see if misfire follows.
Step 4: Check fuel injector on cylinder 4; listen for clicking or perform a balance test.
Step 5: Perform a compression test on cylinder 4 and compare to others.
Step 6: Inspect for vacuum leaks and check engine mechanical timing.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause catalytic converter damage and reduced fuel economy. Short trips to a repair shop are okay.
How much does it cost to fix?▼
Cost varies: spark plugs $50-$150, ignition coil $100-$200, fuel injector $200-$500, compression repairs $500-$1500. Diagnosis fee $100-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.