What Does Code P0158 Mean?
- P0158 definition: O2 Sensor Circuit High Voltage (Bank 2, Sensor 2)
- Issue Severity: MODERATE– Extended driving with this code can cause internal engine damage.
- Repair Urgency: Get this code fixed as soon as possible.
- Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0158 code. This DTC can be triggered by a faulty oxygen sensor, damaged wiring, faulty coolant temperature sensor, or high fuel pressure.
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Oxygen sensor 2 is the downstream oxygen sensor in relationship to the catalytic converter. It measures the amount of air and fuel coming out of the catalytic converter to ensure the catalytic converter is functioning properly. If the voltage is high (approx. .9V) there is an excess of fuel in the mixture. If the voltage is low (approx. .1V) then there is an excess of air in the mixture. Therefore, the downstream oxygen sensor (sensor 2) should produce a steady voltage of approximately 0.45 volts. When trouble code P0158 is set, this indicates that there is a high voltage (steadily above .9 volts) for more than 10 seconds indicating a lack of oxygen in the exhaust stream and an abundance of fuel at sensor 2 on bank 2 of the engine.
- Faulty O2 Sensor
- Short to battery voltage in O2 sensor signal circuit
- Corroded wiring
- Fuel pressure too high
- Engine coolant temperature sensor
- Check Engine Light
- Engine runs rich
- Lower fuel economy
- Rough idle
- Strong fumes
How Do I Fix Code P0158?
With a P0158 code, the first step is to get it properly diagnosed to figure out what is causing the malfunction in the downstream oxygen sensor system. Using the live data function of the FIXD sensor and app allows you to read and analyze engine data to properly diagnose a P0158 code.
If the sensors are all reading correctly, check for any damaged wiring or high fuel pressure. If any of these conditions exist and you’re not comfortable further diagnosing this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs.
These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.
How Much Does It Cost to Fix Code P0158?
If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0158 code.
Possible Repair Costs for P0158
When it comes to making repairs associated with the P0158 code, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.
- Oxygen sensor $200-$300
- Fuel pressure regulator $200-$400
- Engine coolant temperature sensor $150-$200
DIY Steps to Diagnose Code P0158
If you’d like to try to fix code P0158 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Complete diagnosis may require some specialized equipment beyond what the FIXD Sensor can provide, but the biggest challenge for this repair is that internal engine issues could be the root cause of this code. As such, this diagnosis and repair should not be attempted by beginner DIYers.
DIY difficulty level: Beginner
This repair can be attempted by beginner DIYers.
Tools/parts needed (our top picks from Amazon):
STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.
Scan your vehicle to verify P0158 is the only code present. If other codes are present, they must be addressed first.
STEP 2: INSPECT O2 SENSORS AND WIRING.
Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages. If any damage is found, replace the oxygen sensor.
STEP 3: CHECK OXYGEN SENSOR(S) WITH MULTIMETER.
Check voltage at the O2 sensor; if the voltage is steadily high (.9V or higher) the O2 sensor may be faulty. Before replacing, check the following:
- Verify coolant temperature is reading properly (consult vehicle manual for specification)
- Verify fuel pressure is within spec.
STEP 4: CONSULT A PROFESSIONAL.
If at this point the vehicle is still setting the same code, you may have a more serious problem with your car’s oxygen sensor system, and you should bring the vehicle to a certified shop to have further diagnostic work performed.
Common P0158 diagnosis mistakes
Replacing the O2 sensor without checking to see if the vehicle is running rich due to another problem.
Still Need Help Fixing Code P0158?
If you’ve followed the steps above and are still experiencing issues with the oxygen sensor system and code P0158, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals