What Does P1148 Mean?
This code indicates the oxygen sensor-based fuel control system on Bank 2 is running too rich. The ECM has determined that the fuel trim corrections on Bank 2 have reached or exceeded the rich limit, meaning the system is delivering more fuel than needed and cannot compensate further. This code is often manufacturer-specific and commonly seen on Nissan and Infiniti vehicles, where it relates to closed-loop fuel control system performance.
Common Causes
25%
Leaking fuel injector(s) on Bank 2 delivering excess fuel
25%
Faulty Bank 2 upstream O2 or A/F sensor providing inaccurate feedback
20%
Excessive fuel pressure from a failing fuel pressure regulator
15%
EVAP purge valve stuck open introducing excess fuel vapors
15%
MAF sensor contamination causing underreporting of airflow (ECM adds too much fuel relative to actual air)
Diagnostic Steps
1
Monitor Bank 2 short-term and long-term fuel trim values; large negative values confirm the ECM is attempting to remove fuel (rich condition).
2
Compare Bank 1 and Bank 2 fuel trims; if only Bank 2 is rich, the issue is isolated to that side.
3
Check fuel pressure with a gauge; verify it is within spec and drops appropriately when vacuum is applied to the regulator.
4
Inspect Bank 2 spark plugs for black sooty deposits indicating rich combustion.
5
Monitor the Bank 2 upstream O2/A/F sensor output to verify proper operation and response time.
6
Perform an injector balance test to identify any injectors on Bank 2 that may be leaking or flowing excessively.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
This code indicates the oxygen sensor-based fuel control system on Bank 2 is running too rich. The ECM has determined that the fuel trim corrections on Bank 2 have reached or exceeded the rich limit, meaning the system is delivering more fuel than needed and cannot compensate further. This code is o...
The most common cause of P1148 (O2 Control (Bank 2) System too rich) is: Leaking fuel injector(s) on Bank 2 delivering excess fuel
Typical repair costs for P1148 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A rich condition dilutes engine oil with fuel, accelerating engine wear. Excess unburned fuel can overheat the catalytic converter, potentially creating a fire risk in severe cases. Reduced fuel economy is also expected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1148 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel System / Emissions
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
