What Does P029C Mean?
The ECM has determined that the fuel injector on cylinder 1 is restricted, delivering less fuel than commanded. The ECM detects this through individual cylinder fuel trim analysis, where cylinder 1 consistently requires maximum positive fuel correction but still runs lean. This can cause rough idle, misfire on cylinder 1, reduced power, and potential catalytic converter overheating from a lean condition.
Common Causes
45%
Clogged or partially blocked fuel injector nozzle on cylinder 1 from fuel contaminants, varnish, or carbon deposits
20%
Fuel contamination (water, debris, or ethanol separation) blocking the injector's internal passages
15%
Injector pintle or needle valve sticking partially closed due to internal corrosion or deposit buildup
10%
Kinked or restricted fuel supply line to the fuel rail near cylinder 1
10%
Electrical issue causing reduced injector on-time or incomplete valve opening
Diagnostic Steps
1
Perform an injector balance test by individually disabling each injector and measuring RPM drop; cylinder 1 will show a smaller RPM drop than others if restricted.
2
Remove cylinder 1 fuel injector and test on an injector flow bench; compare spray pattern and volume to specification and to other injectors. A restricted injector will show reduced volume and irregular spray.
3
Try a professional fuel injector cleaning service (ultrasonic cleaning) on the cylinder 1 injector; retest flow afterward to see if restriction is cleared.
4
Inspect the fuel filter for contamination and replace if overdue; contaminated fuel is a common root cause for injector restrictions.
5
Measure injector resistance and check for proper voltage supply; an electrical issue reducing the solenoid pull strength can mimic a restricted injector.
Estimated Repair Cost
$50 - $500
Parts + labor, varies by vehicle and location
The ECM has determined that the fuel injector on cylinder 1 is restricted, delivering less fuel than commanded. The ECM detects this through individual cylinder fuel trim analysis, where cylinder 1 consistently requires maximum positive fuel correction but still runs lean. This can cause rough idle,...
The most common cause of P029C (Cylinder 1 - Injector Restricted) is: Clogged or partially blocked fuel injector nozzle on cylinder 1 from fuel contaminants, varnish, or carbon deposits
Typical repair costs for P029C 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 but cylinder 1 will be running lean, which causes elevated exhaust temperatures and can damage the catalytic converter. A lean misfire at highway speeds creates a potential fire risk if the catalytic converter overheats. Repair within a few days.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P029C 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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