What Does P029A Mean?
The ECM has detected that the individual cylinder fuel trim correction for cylinder 1 has reached its maximum enrichment limit. This means the ECM is adding as much extra fuel as it can to cylinder 1, and the air/fuel ratio is still too lean. This indicates a significant lean condition specific to cylinder 1 that the adaptive fuel system cannot fully compensate for. The driver may notice rough idle, misfire, or reduced performance.
Common Causes
35%
Vacuum leak at the cylinder 1 intake port, runner gasket, or nearby intake manifold seal allowing unmetered air
30%
Partially clogged or restricted cylinder 1 fuel injector reducing fuel delivery
15%
Exhaust leak near cylinder 1 causing false lean reading at the oxygen sensor
12%
Low fuel pressure from a weak fuel pump or partially clogged fuel filter affecting cylinder 1 delivery
8%
Cylinder 1 compression issue causing poor combustion and lean exhaust readings
Diagnostic Steps
1
Monitor cylinder 1 individual fuel trim percentage via the scan tool; confirm it is at or near the positive (rich correction) limit, typically +25% to +30%.
2
Perform a smoke test on the intake manifold with focus on the cylinder 1 intake port and runner area; look for smoke escaping from gasket surfaces, vacuum connections, or cracked manifold.
3
Test cylinder 1 injector flow by performing an injector balance test; compare the RPM drop when disabling cylinder 1 vs. other cylinders. A smaller RPM drop suggests reduced fuel delivery.
4
Check fuel system pressure at idle and under load (key-on-engine-running); compare to spec (typically 35-65 psi depending on application). Pressure should hold steady without dropping.
5
Inspect the exhaust manifold at cylinder 1 for cracks or a blown gasket using a visual inspection and by feeling for exhaust pulses with your hand at cold startup.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
The ECM has detected that the individual cylinder fuel trim correction for cylinder 1 has reached its maximum enrichment limit. This means the ECM is adding as much extra fuel as it can to cylinder 1, and the air/fuel ratio is still too lean. This indicates a significant lean condition specific to c...
The most common cause of P029A (Cylinder 1 - Fuel Trim at Max Limit) is: Vacuum leak at the cylinder 1 intake port, runner gasket, or nearby intake manifold seal allowing unmetered air
Typical repair costs for P029A range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven cautiously for short distances. A persistent lean condition on cylinder 1 can cause the catalytic converter to overheat from unburned oxygen, and may eventually cause a misfire leading to catalytic converter damage. Schedule repair within days.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P029A to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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