Fix P0158: Mechanic’s solutions that WORKED

The code P0158: O2 Sensor Circuit High Voltage (Bank 2, Sensor 2) indicates a high voltage issue in the oxygen sensor circuit on Bank 2, Sensor 2. This fault is typically caused by a malfunctioning oxygen sensor or problems in the associated wiring and can lead to decreased fuel efficiency and increased emissions.

P0158 quick overview

Meaning	P0158: O2 Sensor Circuit High Voltage (Bank 2, Sensor 2)
Is it serious?	Yes, it can affect the vehicle’s fuel efficiency and emissions.
Possible causes	– Faulty or contaminated oxygen sensor – Exhaust leaks near the oxygen sensor – Short to voltage in the oxygen sensor signal circuit – Corroded or poor oxygen sensor connector – Faulty fuel pressure or leaking injectors – Damaged or faulty wiring to the oxygen sensor – Issues with the engine control module (ECM)
How to diagnose?	Scan for Codes: Use an OBD-II scanner to confirm the presence of the P0158 code and check for any other related codes. Visual Inspection: Inspect the wiring and connectors related to the oxygen sensor for damage, corrosion, or disconnections. Check Exhaust System: Look for leaks in the exhaust system, particularly near the oxygen sensor. Test Oxygen Sensor: Measure the voltage output of the oxygen sensor to see if it is within the normal range. Fuel System Evaluation: Check the fuel pressure and inspect for leaking injectors that could be affecting the oxygen sensor readings. Load Test Wiring: Perform a load test on the sensor wiring to ensure it can handle the required current. Check for TSBs: Look for any Technical Service Bulletins related to the P0158 code for your specific vehicle model. ECM Check: Consider the possibility of a faulty engine control module if all other diagnostics do not reveal the issue.

How to fix P0158 – learn from mechanics

I looked into P0158 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Toyota

Vehicle Information 2007 Toyota RAV4 Limited 3.5L

Issue + Repair History

• Initially came in for right rear wheel speed no output causing brake light to stay on and set code for right rear.
• Replaced right hub and harness.
• Customer returned with codes P0158 (O2 sensor) and P1578 (brake malfunction).

Other OBD2 Codes + Test Results

• P0158: O2 sensor
• P1578: Brake system

What Are People Suggesting to Fix Issue

• Engine misfire or any ABS system fault may cause VSC MIL back on.
• Toyota’s VSC light comes on anytime the check engine light is on.
• VSS light is triggered when the engine ECU malfunction happens.
• Rear O2 sensor high voltage codes on a newer Toyota might be caused by a faulty front O2 sensor.
• VSC light can come on with a pending code.
• For P0158, check if the O2 sensor has set with a reading over 1 volt, indicating a short in the O2 sensor.
• For P1578, check for codes set in the VSC/ABS ECU.

What Was the Final Fix

• Replaced both bank 2 sensors for O2 sensor codes.
• Replaced pigtail for right rear sensor not reading speeds at times.

Case #2: Dodge

Vehicle Information 2004 Dodge Dakota SLT 3.7L

Issue + Repair History

• Came in with codes P0440 (EVAP malfunction) and P0158 (bank 2 sensor 2 voltage too high).
• Replaced NVLP assembly, purge valve, and gas cap.
• Ran EVAP test on MODIS, failed with same code P0440.

What Are People Suggesting to Fix Issue

• Check the wiring between the NVLD and the PCM, especially near the left front wheel well.
• Check for rotted rubber hoses or elbows, especially at the top of the vapor storage canister.
• Replace the O2 sensor with one from the dealer.
• Check for broken NVLD wiring on the left side above the frame.
• Ask the customer about fueling habits, as a fuel-soaked canister could be an issue.

What Was the Final Fix

• The problem was a corroded connector in front of the door; wire was corroded in the connector.
• Fixed wire, ran EVAP test, and it passed.
• Replaced O2 sensor from the dealer for code P0158.

Case #3: Nissan

Vehicle Information 2001 Nissan Pathfinder LE 3.5L

Issue + Repair History

• MIL lamp on with codes P0420 (cat efficiency below threshold) and P0158 (rear O2 voltage high).
• Signals on front and rear O2 sensors indicated possible cat deterioration.
• O2 code appeared to be lazy at idle.

What Are People Suggesting to Fix Issue

• Replace the rear O2 sensor.
• Send to the dealer for an ECM reprogram for the P0420.
• Replace both sensors on bank one side.

What Was the Final Fix

• Replaced both rear O2 sensors for code P0138.
• This also helped with the P0420 code as the O2 signal was cleaner.
• All monitors complete and vehicle is gone.

Case #4: Jeep

Vehicle Information 2004 Jeep Wrangler Rubicon 4.0L

Issue + Repair History

• Initially had a no-start condition; confirmed and replaced a bad fuel pump.
• Vehicle returned with stalling condition.
• Codes P0157 and P0158 for bank 2 sensor 2 O2 sensor.
• Fuel pressure drops intermittently from 49psi to 10psi.
• Replaced fuel pump relay and ASD relay with no change.

Other OBD2 Codes + Test Results

• P0157: O2 Sensor short to ground bank 2 sensor 2.
• P0158: O2 Sensor short to power bank 2 sensor 2.
• Fuel pressure fluctuating between 50-10 psi.

What Are People Suggesting to Fix Issue

• Disconnect the rear O2 sensor and drive to see if there’s a change.
• Check the fuel regulator for potential issues.

What Was the Final Fix

• Disconnected O2 sensor with no change.
• Found the middle ECM connector filled with engine oil traced back to a leaking oil pressure switch.
• Cleaned terminals, but a new problem with the data bus from the key sentry arose.
• Sent to the dealer, who replaced the ECM, BCM, and programmed new keys.

Case #5: Lexus

Vehicle Information 2011 Lexus ES350 3.5L

Issue + Repair History

• Check engine light on with code P0138 (Oxygen sensor circuit high voltage, Bank 1 Sensor 2).
• Replaced sensor twice with Denso and NGK brands, waiting on a factory sensor.
• Found voltage discrepancy between Bank 1 Sensor 2 and Bank 2 Sensor 2.
• Swapped rear sensors, issue moved to Bank 2 Sensor 2.
• Wiring load tested for 11 amps and found to be good.
• Suspected ECM issue but had the newest software.

Other OBD2 Codes + Test Results

• P0138: Oxygen sensor circuit high voltage (Bank 1 Sensor 2).
• Smoke check: No leaks found.

What Are People Suggesting to Fix Issue

• Replace or swap upstream sensors (B1S1).
• Drive or flatbed to a shop that will cover the warranty.
• Research the problem on Identifix.
• Replace all sensors as a preventative measure.
• Load test wires, especially near the exhaust pipe.
• Check the earth system.

What Was the Final Fix

• Replaced Bank 1 Sensor 1 (B1S1) after Identifix research indicated it as the cause.
• Fuel trim values improved and Bank 1 Sensor 2 voltage normalized.
• Road tested for 7 miles, readiness monitors passed except for the evap system.

Advice	Description of Diagnostic Step
Check O2 Sensor Wiring	Inspect the wiring and connectors for the O2 sensors, looking for damage, corrosion, or loose connections.
Replace O2 Sensor	If the O2 sensor is faulty, replace it with a new one, preferably an OEM part.
Inspect Fuel System	Check for issues with the fuel system, including the fuel pump, fuel pressure, and injectors.
Check for Exhaust Leaks	Inspect the exhaust system for any leaks, especially between the engine and the O2 sensor.
Consider Related Components	Evaluate components that might affect O2 sensor readings, such as catalytic converters or upstream O2 sensors.
Perform ECM/PCM Software Updates	Ensure the vehicle’s computer has the latest software updates, as this can sometimes resolve sensor issues.
Load Test Wiring	Conduct a load test on the O2 sensor wiring to ensure it can handle the required current without issues.
Check for Technical Service Bulletins (TSBs)	Look for any manufacturer TSBs related to the fault code, as they may provide specific repair guidance.