1996 Chevy S10 4.3L V6 P0143 Bank 1 Sensor 3 Low Voltage Issue After O2 Sensor Replacement
I have a 1996 Chevrolet S10 ZR2 with a 4.3L V6 Vortec engine. The check engine light activated, and the diagnostic scan revealed code P0143 — Bank 1 Sensor 3 Oxygen Sensor indicating low voltage. Previously, there was a weld defect in the exhaust pipe before the catalytic converter, which I had repaired to fix pinhole leaks. After replacing the Bank 1 Sensor 3 (B1S3) oxygen sensor, I cleared the codes and the check engine light initially went off. However, within an hour, the check engine light returned, and the code P0143 reappeared — specifically indicating low voltage from B1S3. I inspected all wiring connections to the O2 sensor and found no signs of fraying or melting. A local mechanic suggested checking the single-pin connection between the Powertrain Control Module (PCM) and the B1S3 oxygen sensor. Are there any other recommended troubleshooting steps for this issue? Any insights on how to properly diagnose a P0143 fault in a 1996 Chevy S10 V6?
Please confirm all stored diagnostic codes. Use your OBD2 scanner to measure the actual voltage output from the B1S3 oxygen sensor and review the freeze frame data. Also check key parameters like ECT (Engine Coolant Temperature), MAP (Manifold Absolute Pressure), and FTP (Fuel Trim) values during the fault condition. Any modifications to the exhaust system — especially non-stock changes — could interfere with O2 sensor readings. Please share if your vehicle has any aftermarket parts or modifications installed.