01 How Low Can Tire Pressure Be Before It Becomes Unsafe to Dr… • 02 These Simple Car Maintenance Hacks Have Never Been This Easy • 03 Fix This First If Your Car Won’t Start (Before Calling a Me… • 04 The 30-60-90K Maintenance Schedule Explained: What Your Dea… • 05 How to Fix a Car Engine That Stops Abruptly and Won't Start • 06 Direct Injection's Dark Secret: How Modern Engines Destroy … • 07 The Sneaky Mechanical Piece That Increases Fuel Consumption… • 08 Why Your Car Revs High But Doesn’t Go Fast • 09 The Hidden Truth About Why Rear Brake Pads Wear Out So Quic… • 10 Why Your Car Shakes After Repairs and What It Really Means •

DTC codes / P21xx · Fuel and air metering / P21A0

P21A0Cylinder 5 Air-Fuel Ratio Imbalance

P21A0 indicates that the powertrain control module has detected an air-fuel ratio imbalance on cylinder 5, meaning that cylinder's combustion is not matching the fuel and air delivered to the other cylinders. The computer monitors crankshaft speed fluctuations and oxygen sensor feedback to flag this specific cylinder as deviating from the expected balance.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage