1996 Grand Am 2.4L Engine P0134 O2 Sensor Code Reappears After Replacement
My 1996 Grand Am with a 2.4L engine is consistently throwing a P0134 oxygen sensor code for Bank 1, Sensor 1. I've replaced the sensor twice and cleared the code using my OBD-II scanner, but the fault returns every time. The spark plugs appear normal, and the oxygen sensor tip shows no visible damage. I'm at a loss as to what might be causing this. Does the oxygen sensor ground directly to the engine in older 1996 Grand Am models? If so, could a poor ground connection be the root cause? Any guidance or troubleshooting steps would be greatly appreciated.
What exact code are you seeing? P0134 is common in 1996 Grand Am models, which used a single-wire oxygen sensor with the ground connected to the exhaust manifold. Later model years had a separate ground wire running to an engine compartment stud. P0133 can also be triggered by other components. If you're seeing P0134, circuit testing is required. Without a scan tool that provides live data, you'll need to perform backprobing using test pins or a wire piercing probe to measure voltage at various points with a digital multimeter. If you don't have the right tools, it's best to visit a shop specializing in electrical diagnostics and certified ASE technicians. You can't diagnose this issue by guessing—actual testing is essential. First, confirm the exact code and its enabling conditions before proceeding.