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P0158 and P0137 OBD2 Fault Codes in 2007 FJ Cruiser: Causes and Fixes

Model: 2007 FJ Cruiser Fault Code: P0137 Posted: 2012-08-26 14:57

Hi everyone, I've been experiencing recurring OBD2 fault codes P0158 and P0137 on my 2007 FJ Cruiser. These codes usually appear individually or occasionally together—though it's unusual for both to occur simultaneously. Is this a rare occurrence, or am I missing something? I suspect faulty oxygen (O2) sensors are the root cause, but I'd like to confirm if there could be another underlying issue. Previously, I had P0420 and P0430 codes due to modifications such as an air intake system and long-tube headers with catalytic converters removed. After those changes, the fault codes shifted to P0158 and P0137. I'm now wondering if removing the catalytic converter is affecting sensor readings. Any insights or troubleshooting steps would be greatly appreciated!

Related fault codes

P0137P0158

Comments (3)

Anonymous 2012-08-26 15:59

If you're in the U.S., it's important to note that catalytic converters are legally required. Removing them can cause O2 sensor codes like P0158 and P0-137 because the sensors operate outside their intended environment. Both P0158 and P0137 relate to post-catalyst oxygen sensors—without a functioning catalytic converter, these sensors cannot read properly due to abnormal exhaust gas composition. The engine control module (PCM) detects this mismatch and triggers the codes. Recommended steps: - Inspect wiring harnesses and sensor connections for damage, fraying, or shorts. - Check the heater circuit of each O2 sensor—ensure proper heating function. - Verify reference voltage and signal integrity. - Confirm whether any other diagnostic trouble codes (DTCs) are present. If not, this may point to a sensor or wiring issue specifically related to post-cat sensors.

Anonymous 2012-08-28 04:42

I’ve checked my sensors—sensor 2 on bank 2 shows low voltage, while sensor 2 on bank 1 reads high voltage. This seems inconsistent because both sides should typically show similar voltage behavior (either both high or both low). So why am I getting P0137 and P0158 instead of the expected P0137/P0157 or P0158/P0138? I’m not very familiar with O2 sensor operation, so any clarification on this would be really helpful. The codes usually appear within the first 15 minutes of driving—sometimes both at once. Is this a sign of a deeper issue like faulty wiring or sensor failure?

Anonymous 2012-08-28 08:29

As mentioned, knowing the actual voltage readings from each O2 sensor as reported by the PCM is essential for accurate diagnosis. Without live data, troubleshooting becomes challenging. Start with a basic inspection of all sensors: check wiring integrity, look for chaffing or shorts, verify heater circuit functionality (heater to signal), and ensure reference voltage and ground connections are intact. Also, confirm whether the O2 sensor heater fuses are properly connected—these can fail silently. I’m curious—why did you remove the catalytic converters? This modification may be directly contributing to erratic sensor readings and triggering these specific codes.