P0151 Low signal level in the oxygen sensor circuit B2S2

Datasheet P0151

P0151 - O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

What does trouble code P0151 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

Essentially the same as P0136, P0137, and P0131, the P0151 code refers to the first oxygen sensor on bank 2. P0151 means the O2 oxygen sensor voltage has remained low for more than 2 minutes.

The ECM interprets this as a low voltage condition and sets the MIL. Bank 2 Sensor 1 is located in front of the catalytic converter.

Symptoms

The driver may not see any visible symptoms other than the MIL (Check Engine / Service Engine Soon) lighting.

• A low O2 sensor voltage causes the ECM to richen the mixture in the engine.
• The Check Engine light will come on.
• You may have exhaust leaks up to or near the O2 sensor in question. Exhaust leaks can be larger when the engine is cold and decrease as the engine warms up.

Causes of the P0151 code

The P0151 code may mean that one or more of the following events have occurred:

• The engine control module (ECM) sees that the O2 sensor voltage for bank 1 sensor 2 is below 0,21 V when the ECM has commanded a rich fuel on that bank.
• Exhaust leaks before the sensor introduces excess oxygen into the exhaust, causing the O2 sensor to read excess oxygen and the ECM running on enrichment.
• Defective oxygen sensor o2
• Short circuit on voltage in a signal chain O2
• High resistance or open in O2 signal circuit

Possible solutions

• Repair the short, open, or high resistance in the o2 signal circuit.
• Replacing the O2 Sensor for Bank 1 Sensor 2 If All Tests Point to a Bad Sensor
• Repair or replace wiring or connection to O2 sensor bank 2 sensor 1
• Elimination of exhaust gas leaks in front of the sensor, due to which excess oxygen enters the exhaust gases.

How does a mechanic diagnose a P0151 code?

• Scans codes and documents, captures frame data, then clears codes to confirm failure
• Monitors O2 sensor data to see if voltage switches between low and high at a high rate compared to other sensors.
• Checks O2 sensor wiring and harness connections for corrosion at the connections.
• Checks the O2 sensor for physical damage or fluid contamination; repairs any leaks before replacing the O2 sensor
• Checks for exhaust leaks ahead of the sensor, repairs the leaks, and retests the sensor.

Common Mistakes When Diagnosing Code P0151

Follow these simple guidelines to prevent misdiagnosis:

• Repair any exhaust leaks upstream of the sensor to prevent excess oxygen from entering the exhaust stream causing low voltage readings.
• Repair oil or coolant leaks that may contaminate or clog sensors.

How serious is the P0151 code?

• The output voltage of the O2 sensor may be due to an exhaust leak, causing the O2 sensors to produce low output voltages indicating excess oxygen in the exhaust stream.
• The ECM cannot control the fuel/air ratio in the engine if the O2 sensor is defective. This will result in poor fuel economy and excess fuel will foul the spark plugs over time.

Additional comments to consider regarding code P0151

The O2 sensor circuit for bank 1 sensor 2 is used to provide voltage feedback to the ECM indicating how much oxygen is in the exhaust stream to help the engine control the air/fuel ratio. A low voltage condition indicates an excess of oxygen in the exhaust gases.

How to Fix P0151 Engine Code in 4 Minutes [3 DIY Methods / Only $9.65]

Need more help with your p0151 code?

If you still need help with DTC P0151, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.