Check engine light w/ code P0158

nonlocality · **Joined:** Tue Mar 24, 2020 1:27 pm **Posts:** 11

My check engine light has been on for quite some time, and the first code was read at Autozone, and they told me it was my O2 sensor. I replaced all 4 O2 sensors, bought my own scan tool to check the check engine light, and now I get P0158 code which is high voltage bank 2 sensor 2. I've tried switching the O2 sensors around to see if it was maybe a bad O2 sensors, but still the same code. I've also checked all fuses and the wiring/ connectors for any visible signs of damage, and nothing. I'm completely stumped, and don't know where to go from here. I'd rather exhaust all options before I take it to a mechanic or a dealership. Any suggestions, advice, or help would be very much appreciated. Thank you!

WWDiesel · **Posted:** Sat Apr 09, 2022 10:10 pm

FYI:
A P0158 code is not typically serious. It simply means that there is a problem in the bank 2, sensor 2 circuit and the power control module (PCM) has stored a code for future reference. There are little to no adverse effects on vehicle performance when this trouble code is present.
See this:> https://www.engine-codes.com/p0158_jeep.html

Does your scanner provide real time data so you can monitor the voltage signal coming from the O2 sensors on that bank? If the downstream sensor is high, then the upstream should also be running high.

From EngineCodes.com wrote:

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases (lean condition), the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below <0.45 V. If the oxygen in the exhaust gas decreases (rich condition), the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above >0.45 V.

In your situation, you are getting a "Rich" condition (high voltage) signal to the PCM.
Since you have ruled out the O2 sensor by replacing it,
These are some of the possible causes listed:

Failed rear oxygen sensor

Image from https://www.engine-codes.com/p0158_jeep.html

nonlocality · **Joined:** Tue Mar 24, 2020 1:27 pm **Posts:** 11

WWDiesel wrote:

FYI:
A P0158 code is not typically serious. It simply means that there is a problem in the bank 2, sensor 2 circuit and the power control module (PCM) has stored a code for future reference. There are little to no adverse effects on vehicle performance when this trouble code is present.
See this:> https://www.engine-codes.com/p0158_jeep.html

Does your scanner provide real time data so you can monitor the voltage signal coming from the O2 sensors on that bank? If the downstream sensor is high, then the upstream should also be running high.

From EngineCodes.com wrote:

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases (lean condition), the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below <0.45 V. If the oxygen in the exhaust gas decreases (rich condition), the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above >0.45 V.

In your situation, you are getting a "Rich" condition (high voltage) signal to the PCM.
Since you have ruled out the O2 sensor by replacing it,
These are some of the possible causes listed:

Failed rear oxygen sensor

Image from https://www.engine-codes.com/p0158_jeep.html

Thank you for info. So all four O2 sensors provide a voltage reading of 1.27 with the ignition on and the car off. When I start it, the readings for all but one O2 sensor jump around, while the bank 2 sensor 2 reading stays at 1.27, which makes me think something might be wrong with the connectors or wiring of that sensor. I wouldn't care to much about it, but I need it fixed in order to pass emissions and renew my registration! Thank you again for all the help and info.

WWDiesel · **Posted:** Sun Apr 10, 2022 3:44 pm

With the voltage remaining constant, you have a broke wire or a bad connection at the O2 sensor or at the PCM, or somewhere in-between.
Should be quite simple to find!
I would check for continuity of the wire between the sensor and the PCM using an ohm meter.

nonlocality · **Joined:** Tue Mar 24, 2020 1:27 pm **Posts:** 11

Cheers, will do, and thank you again!

Check engine light w/ code P0158

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