P1151 Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
Quick Answer
The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Common causes include Faulty Upstream Oxygen Sensor Bank 2, Fuel pressure high or low, MAF sensor dirty/defective. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P1151 indicates Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2.
- Common causes
- Common causes include Faulty Upstream Oxygen Sensor Bank 2, Fuel pressure high or low, MAF sensor dirty/defective.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P1151 Description
• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.
• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.
• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.
• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.
• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by
measuring the current going through the heater circuit.
• The MIL is activated after a fault is detected on two consecutive OBD II drive cycles.
What are the Possible Causes of the DTC P1151?
- Faulty Upstream Oxygen Sensor Bank 2
- Fuel pressure high or low
- MAF sensor dirty/defective
- Vacuum leak on engine
- Leaking fuel injector or fuel pressure regulator
- Faulty Powertrain Control Module (PCM)
How to Fix the DTC P1151?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1151 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific Makes
- P1151 Audi — Bank 1 Long Term Fuel Trim Range 1 Lean Lower Limit Exceeded
- P1151 BMW — O2 Sensor Heater Circuit Signal Intermittent Bank 2 Sensor 1
- P1151 Chrysler — Fuel Rail Pressure Malfunction Maximum Positive Deviation
- P1151 Dodge — Fuel Rail Pressure Malfunction Maximum Positive Deviation
- P1151 Ford — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
- P1151 Hyundai — Electronic Throttle System Main Accel Position Sensor 2 Malfunction
- P1151 Jeep — Fuel Rail Pressure Malfunction Maximum Positive Deviation
- P1151 Lexus — Coolant Heat Storage Tank
- P1151 Lincoln — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
- P1151 Mazda — HO2S-21 Lean Condition Correcting For Over Rich Condition
- P1151 Mercury — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
- P1151 MINI — O2 Sensor Heater Circuit Signal Intermittent Bank 2 Sensor 1
- P1151 Subaru — Rear Oxygen Sensor Heater Circuit High Input
- P1151 Suzuki — HO2S21 Circuit Low Voltage Shift/High Voltage Shift/Circuit Continuity/High Voltage
- P1151 Toyota — Coolant Heat Storage Tank
- P1151 Volkswagen — Bank 1 Long Term Fuel Trim Range 1 Lean Lower Limit Exceeded
Frequently Asked Questions about P1151 Code
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