What Does P02A4 Mean?
The ECM has determined that the fuel injector on cylinder 3 is restricted, meaning it is not delivering the full amount of fuel commanded by the ECM. The individual cylinder fuel trim for cylinder 3 has maxed out its enrichment capability, and the ECM has identified the injector as the source of the lean condition. The driver may experience rough idle, cylinder 3 misfire, hesitation, and potential lean-related exhaust issues.
Common Causes
45%
Clogged cylinder 3 injector nozzle from fuel deposits, varnish, or carbon buildup on the tip
20%
Fuel contamination (water, rust, or sediment) partially blocking the injector internal passages
15%
Injector needle or pintle partially seized from internal corrosion, limiting fuel flow
10%
Fuel supply irregularity at the cylinder 3 position on the fuel rail
10%
Electrical fault causing reduced injector solenoid pull force or shortened on-time
Diagnostic Steps
1
Perform an injector balance test by disabling each injector individually and comparing RPM drops; cylinder 3 should show a smaller RPM drop if the injector is restricted.
2
Remove the cylinder 3 injector and test on a flow bench; compare spray pattern, atomization, and flow volume against specification and other injectors from the engine.
3
If flow is reduced, attempt professional ultrasonic cleaning of the injector; retest flow. If flow does not recover to within 5% of spec, replace the injector.
4
Replace the fuel filter and inspect a fuel sample for water, sediment, or discoloration that could indicate contaminated fuel supply.
5
Verify injector electrical operation: measure coil resistance, check for 12V supply at the connector, and use a noid light to confirm the ECM is commanding proper pulse width.
Estimated Repair Cost
$50 - $500
Parts + labor, varies by vehicle and location
The ECM has determined that the fuel injector on cylinder 3 is restricted, meaning it is not delivering the full amount of fuel commanded by the ECM. The individual cylinder fuel trim for cylinder 3 has maxed out its enrichment capability, and the ECM has identified the injector as the source of the...
The most common cause of P02A4 (Cylinder 3 - Injector Restricted) is: Clogged cylinder 3 injector nozzle from fuel deposits, varnish, or carbon buildup on the tip
Typical repair costs for P02A4 range from $50 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Limited driving is acceptable. A restricted injector creates a persistent lean condition on cylinder 3 that elevates exhaust temperature and can damage the catalytic converter. Avoid sustained high-load driving (towing, mountain passes) as the lean condition worsens under load.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02A4 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Generic (SAE)
Recommended Tools
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