What Does P1151 Mean?
This code indicates the upstream heated oxygen sensor on Bank 2 is not switching between lean and rich as expected and is stuck indicating a persistent lean condition. The ECM has detected that the Bank 2 Sensor 1 voltage remains below 0.45V for an extended period. This is the Bank 2 equivalent of P1131 and indicates either a genuine lean running condition on Bank 2 or a sensor that has become biased toward lean readings.
Common Causes
35%
Vacuum leak at Bank 2 intake manifold gasket, vacuum hoses, or PCV connections
25%
Faulty Bank 2 upstream O2 sensor biased lean or with slow response
18%
Low fuel pressure or restricted fuel delivery to Bank 2 cylinders
12%
Clogged or partially restricted fuel injector(s) on Bank 2
10%
Exhaust leak upstream of the Bank 2 O2 sensor allowing false air readings
Diagnostic Steps
1
Monitor Bank 2 short-term and long-term fuel trim values; high positive values confirm a lean condition on that bank.
2
Perform a thorough smoke test focusing on the Bank 2 side of the intake manifold, vacuum hoses, and PCV system.
3
Watch the Bank 2 Sensor 1 O2 voltage waveform at 2500 RPM steady state; verify it oscillates between 0.1V and 0.9V.
4
Compare Bank 1 and Bank 2 fuel trims; if both banks are lean, suspect a common component (fuel pump, MAF).
5
Check fuel pressure with a mechanical gauge at idle and under load.
6
Inspect the Bank 2 exhaust manifold and flange connections for exhaust leaks near the upstream O2 sensor.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
This code indicates the upstream heated oxygen sensor on Bank 2 is not switching between lean and rich as expected and is stuck indicating a persistent lean condition. The ECM has detected that the Bank 2 Sensor 1 voltage remains below 0.45V for an extended period. This is the Bank 2 equivalent of P...
The most common cause of P1151 (Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2) is: Vacuum leak at Bank 2 intake manifold gasket, vacuum hoses, or PCV connections
Typical repair costs for P1151 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A persistent lean condition on Bank 2 can cause elevated combustion temperatures, increasing the risk of engine misfires and potential catalytic converter overheating. Extended operation may cause piston or valve damage in severe cases.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1151 to identify the root cause.
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Quick Info
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Powertrain
System
Fuel System / Emissions
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