P0131 and P0151 O2 Sensor Low Voltage Issue - 1996 Chevy Silverado 1500 5.7L

Since there are two oxygen sensors on different engine banks, the most likely cause might be that both sensors have failed. This is uncommon unless one sensor failed and was ignored before the second one failed—though not impossible. I’d suspect a wiring problem or an exhaust restriction more than a faulty sensor. Also, it’s possible someone replaced the original sensors with aftermarket ones (like Bosch) that aren’t properly functioning.

I recently replaced both oxygen sensors, and they were the original equipment manufacturer (OEM) parts—still showing the same P0131 and P0151 codes after replacement.

If replacing the sensors didn’t resolve the issue, then the problem may lie in the wiring harness leading to those sensors. Check for blown fuses or damaged wires, especially near the exhaust manifold or sensor locations.

If it's not a wiring issue, a common cause in older vehicles is a clogged catalytic converter. A blocked cat can cause oxygen sensors to register low voltage because they don’t receive enough exhaust gas flow to generate accurate signals. This leads to a rich fuel mixture, which may result in reduced engine performance and poor fuel economy.

I'm experiencing a noticeable power loss when accelerating—my truck almost loses speed and feels like it's hopping. Is there any way to test the catalytic converters to see if they're clogged?

Try removing both oxygen sensors and driving the vehicle again. If the fault codes disappear or engine performance improves, then the issue is likely a restricted exhaust system. Alternatively, install a vacuum gauge on the intake manifold and monitor for positive pressure during acceleration—this can indicate backpressure from a clogged cat.