What Does P02A8 Mean?
The ECM has determined that the fuel injector on cylinder 4 is restricted, delivering less fuel than the commanded amount. The individual cylinder fuel trim for cylinder 4 has reached its maximum positive correction, and the ECM has identified the injector as the root cause of the lean condition. The driver may notice rough idle, a cylinder 4 misfire, hesitation during acceleration, and potential lean exhaust conditions.
Common Causes
45%
Clogged or partially blocked cylinder 4 injector nozzle from fuel varnish, deposits, or contamination
20%
Contaminated fuel with water, sediment, or ethanol separation blocking the injector passages
15%
Injector needle or pintle partially seized from internal corrosion or deposit accumulation
10%
Fuel rail supply issue or localized pressure drop at the cylinder 4 position
10%
Electrical fault reducing injector solenoid pull strength or effective pulse width
Diagnostic Steps
1
Perform an injector balance test by disabling each injector individually; cylinder 4 should show a reduced RPM drop compared to other cylinders if the injector is restricted.
2
Remove the cylinder 4 fuel injector and test on an injector flow bench; compare spray pattern quality, atomization, and flow volume against specification and other injectors.
3
Attempt professional ultrasonic cleaning of the cylinder 4 injector; retest flow after cleaning. If flow does not recover to within 5% of specification, replace the injector.
4
Inspect the fuel filter and replace if overdue; pull a fuel sample from the rail or filter to check for water, rust, or sediment contamination.
5
Check injector electrical circuit integrity: measure solenoid resistance (compare to spec), verify 12V supply at connector, use a noid light to confirm ECM is commanding correct pulse width.
Estimated Repair Cost
$50 - $500
Parts + labor, varies by vehicle and location
The ECM has determined that the fuel injector on cylinder 4 is restricted, delivering less fuel than the commanded amount. The individual cylinder fuel trim for cylinder 4 has reached its maximum positive correction, and the ECM has identified the injector as the root cause of the lean condition. Th...
The most common cause of P02A8 (Cylinder 4 - Injector Restricted) is: Clogged or partially blocked cylinder 4 injector nozzle from fuel varnish, deposits, or contamination
Typical repair costs for P02A8 range from $50 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven short distances at reduced load. A restricted injector creates a lean cylinder that runs hotter than normal, risking catalytic converter damage from elevated exhaust temperatures. Avoid sustained high-load driving until the injector is serviced or replaced.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02A8 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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