Fix P0152: Mechanic’s solutions that WORKED

The code P0152: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1) points out a fault in the oxygen sensor circuit, indicating that the voltage signal from the oxygen sensor in Bank 2, Sensor 1, is higher than normal. This typically suggests a rich-running condition, where the engine is burning more fuel than air. It’s most likely caused by issues with the oxygen sensor itself or problems in the fuel system.

P0152 quick overview

Meaning	P0152: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
Is it serious?	Yes, it can lead to poor engine performance, increased emissions, and reduced fuel economy.
Possible causes	– Faulty or contaminated oxygen sensor – Exhaust leak near the oxygen sensor – Short to voltage in the oxygen sensor signal circuit – Fuel pressure too high – Leaking fuel injectors – Faulty fuel pressure regulator – Engine coolant temperature sensor issues – PCM software needing an update
How to diagnose?	1. Verify the code with an OBD-II scanner. 2. Inspect the oxygen sensor and its wiring for any visible damage or contamination. 3. Check for exhaust leaks near the sensor. 4. Measure the fuel pressure to ensure it’s within the manufacturer’s specifications. 5. Perform a fuel injector leak down test. 6. Check the engine coolant temperature sensor readings. 7. Look for any Technical Service Bulletins (TSBs) or recalls related to the issue. 8. Consider updating the PCM software if applicable.

In simple terms, this code means that one of the sensors measuring the amount of oxygen in the exhaust is sending a signal that’s too high, which usually means there’s too much fuel in the mix. It’s like your car is eating too much and not exercising enough, which isn’t healthy for it. It’s important to get it checked out and fixed to keep your car running smoothly and efficiently.

How to fix P0152 – learn from mechanics

I looked into P0152 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: Dodge

Vehicle Information
1998 Dodge Ram 2500 8.0L

Issue + Repair History

• Customer noticed a gas smell and suspected misfire.
• Drove approximately 8 miles before the MIL (Malfunction Indicator Lamp) illuminated.
• Code P0152 (O2 sensor voltage high) was retrieved.
• Both O2 sensors initially stuck at 1.2V on startup for 10-15 seconds, then began switching normally.
• Concern about the sensors hitting 0.040V for a low and 0.950V for a high.
• Uncertainty about the code setting criteria for this truck.

Other OBD2 Codes + Test Results

• Sensor test passed.

What Are People Suggesting to Fix Issue

• Ensure engine runs for more than 2 minutes with coolant temp above 170 degrees F, as DTC sets when voltage is above 1.2 volts.
• Possible intermittent short in O2 sensor heater causing high voltage reading.
• Check fuel pressure regulator for leak into vacuum and leakdown of injectors after shutoff.

What Was the Final Fix

• Oxygen sensor was found to flatline at 1.2V after about 15 minutes of run time.
• Replacing the oxygen sensor resolved the issue.

Case #2: Chrysler

Vehicle Information
2002 Chrysler Concorde LX 2.7L

Issue + Repair History

• Initially came in with P0155 (B2S1 heater malfunction).
• Sensor tested bad, replaced, and vehicle released.
• MIL returned with P0152 stored; all O2 sensors flatlining at 0.3V.
• Replaced B2S1 with a known good sensor; other 3 sensors still flatline at 0.3V.
• After road test, P0152 returned with B2S1 flatlining at 0.1V and others at 0.3V.
• All splices, connectors, and grounds tested okay.
• Voltage at heater control 9.8V, 0.1 OHM to ground.
• O2 sensor signal 4.9V, return 2.5V (measured with sensor unplugged).
• Replaced both upstream O2 sensors and PCM reflash performed.
• Vehicle released but returned with P0300 (random misfire) and flashing MIL light.
• All OBD monitors complete with no sign of initial problem returning.
• Unable to reproduce the new problem, checked all engine and PCM grounds, even soaked engine bay with water.

Other OBD2 Codes + Test Results

• P0152- O2 sensor voltage high B2S1

What Are People Suggesting to Fix Issue

• Check for software update for O2 codes.
• Use NTK or Mopar O2 sensors.
• TSB 18-031-02 calls for PCM reflash for similar O2 sensor codes.
• Test for continuity between the PCM and sensors.
• Hard wiring the O2 circuits can fix issues with internal wiring breakdown.
• Flashing the PCM and replacing sensors as one bad sensor can affect others.

What Was the Final Fix

• Found a poor ground connection at the PCM.
• Cleaned and repaired the connection.
• After test driving and checking monitors, the issue seemed resolved.

Case #3: Jeep

Vehicle Information
2004 Jeep Wrangler X 4.0L

Issue + Repair History

• Vehicle brought in for cutting out issue.
• Customer insisted on replacing the fuel pump without testing, based on dealership diagnostics.
• Fuel pump replaced, but the problem persisted.
• Scanned for DTCs and found O2 sensor codes (P0151, P0152) and TPS voltage high (P0123).
• Tested TPS sensor with no signs of flat spots or dropouts.
• Replaced crank sensor and both O2 sensors, but the issue remained.
• Vehicle cuts out at about 2000 to 2500 RPMs, suspected TPS issue.
• Exhaust and fuel pressure retested, both okay.

Other OBD2 Codes + Test Results

• P0151- O2 sensor voltage high
• P0152 – O2 sensor voltage high
• P0123- TPS voltage high
• Wiring and connections to TPS sensor okay.
• O2 sensors wiring and connections test okay.

What Are People Suggesting to Fix Issue

• Check if the vehicle is running rich and adjust accordingly.
• Inspect coolant sensor, MAP, or MAF for issues causing increased fuel.
• Ensure ECM pins are not bent and check for intermittent connections.
• Capture data stream during failure to see if CRK signal drops out.
• Use dealer parts, especially for O2 sensors, as aftermarket ones can cause repeat codes.
• Check wiring at PCM and wiggle connectors to induce the problem.

What Was the Final Fix

• The problem was the ASD (Automatic Shutdown) relay back feeding and killing the spark.
• Swapped with the starter relay which fixed the concern.
• Noted that the vehicle had aftermarket Bosch O2 sensors and advised the customer to get factory parts.

Case #4: Pontiac

Vehicle Information
1998 Pontiac Firebird Trans Am 5.7L

Issue + Repair History

• Car runs fine until it gets hot and is left to sit for 15-20 minutes.
• Upon restart, it develops a misfire mostly on bank 2 cylinders 4, 6, 8.
• Misfire not always detected by scan tools.
• Fuel pressure readings consistent, hot or cold engine.
• Codes P0154 and P0300 were in memory upon arrival.
• After hot soak, code P0152 set in, but vehicle has not set misfire code again.
• Misfire resolves after 3-5 minutes of running.
• No ignition leakage found in plugs and boots.
• Calibration update performed by dealer, which improved vehicle performance.

Other OBD2 Codes + Test Results

• P0300- Random misfire
• P0154- O2 sensor no activity bank 2 sensor 1
• P0152- O2 sensor high bank 2 sensor 1
• Fuel pressure KOEO pump run – 61 psi
• Fuel pressure KOEO pump stop – 55 psi
• Fuel pressure KOER – 60-62 psi
• KOEO fuel pressure drops – 15-25 psi in 10 min.

What Are People Suggesting to Fix Issue

• Check for an injector bleeding down when hot.
• Inspect O2 sensor operation and wiring.
• Check for recalls and TSBs; consider warranty coverage.
• Investigate possible intake leak on the affected head.
• Look for water in the distributor from a leaking water pump.
• Check for moisture in O2 connector or replace O2 sensor.
• Check for leaking injectors on affected cylinders.

What Was the Final Fix

• Sent car to dealer for control module update.
• After receiving the vehicle from the dealer, it ran better with no more MIL or missing cylinders.

Case #5: Chevrolet

Vehicle Information
1997 Chevrolet Blazer 4.3L

Issue + Repair History

• Intermittent check engine light with code P0152 (O2 signal high bank 2 sensor 1).
• Replaced fuel pressure regulator, both forward O2 sensors, and completed a full tune-up.
• Bank 2 fuel trim goes very negative, indicating a rich condition.
• After replacing several parts, the issue persisted.
• Eventually found a leaking injector on the right bank after several tests.
• Initially assumed no fuel pressure drop after key off meant no leaking injectors, which was incorrect.

Other Test Results

• Fuel pressure – 55 lbs.

What Are People Suggesting to Fix Issue

• Check for raw fuel around the injector, and inspect the EGR for dirt due to overfueling.
• Inspect the O2 sensor harness for chafing or melting near the right side exhaust manifold.
• Check for water entry into the O2 sensor harness connector causing corrosion.
• Watch O2 voltages on the scanner, especially during cold start.
• Perform an injector flow/balance test to ensure good injectors.
• Check if fuel pressure holds after the pump shuts off.
• Inspect the fresh air boot for leaks before the MAF sensor.
• Look for a clean area in the intake manifold, which could indicate a leaking fuel regulator.

What Was the Final Fix

• Found a leaking injector on the right bank.
• Replaced the injector, which resolved the rich condition and the check engine light.

Common Advice	Diagnostic Step Description
Check O2 Sensors	Inspect O2 sensors for proper operation and wiring issues.
Inspect Fuel Pressure	Test fuel pressure to ensure it’s within the proper range and holds after the engine is turned off.
Examine Fuel Injectors	Perform a leak down or flow test on injectors to check for leaks or malfunction.
Update Calibration/Software	Check for updates to the vehicle’s control module or PCM and perform updates if available.
Verify Wiring and Connectors	Inspect wiring harnesses, especially those near hot components like exhaust, for damage or corrosion.
Use OEM Parts	Prefer original equipment manufacturer (OEM) parts, especially for O2 sensors, to avoid repeat issues.
Check for TSBs or Recalls	Look up any Technical Service Bulletins (TSBs) or recalls that might pertain to the issue.