I'm looking for information about the P1133 fault code on my 2001 Buick Regal with a 3800 engine. This code relates to an oxygen (O2) sensor. Where is this sensor located? What tools are required to remove and replace it? Can I test it using a digital multimeter (DVOM)? Any recommendations for reliable replacement sensors like Denso, Bosch, or Standard? Thanks! djjsc@juno.com
The P1133 code points to the upstream oxygen sensor on Bank 1 of the 2001 Buick Regal. This vehicle typically has three O2 sensors: two upstream (before the cat) and one downstream (after). The correct sensor is Bank 1 Sensor 1, located on the driver's side, just in front of the catalytic converter. Some sources suggest this car model may have a 4-wire O2 sensor, which is common in later models. Testing with a DVOM isn't reliable for diagnosing P1133 — the issue lies in sensor signal switching, not voltage readings. I recommend avoiding universal-fit sensors unless you're prepared to use your new O2 socket repeatedly. For reliability, choose Denso over Bosch, which has known quality control issues. Standard may be acceptable but less proven. I'm not willing to pay $400 for OEM parts — a quality aftermarket sensor is more cost-effective. Always get the right part for your specific engine model. Thanks for the insight!
Bank 1 Sensor 1 — this is the upstream O2 sensor on the driver's side (Bank 1). Avoid universal-fit sensors; they often don't perform well in long-term use. Instead, opt for a Denso sensor, which offers better reliability and performance compared to Bosch. This choice reduces failure rates and improves engine efficiency. Good luck with your repair!
Bank 1 Sensor 1 — upstream position on the driver's side. Avoid universal-fit sensors unless you're okay using your new O2 socket repeatedly. I recommend Denso over Bosch due to consistent quality and fewer defects. Thanks for the advice! I found a reliable replacement at a wrecker, and it seems only late-model Buick Regals have the 4-wire version. All is well now — thanks again!
Great to hear you've resolved the issue! Wishing you continued success with your vehicle maintenance.
The O2 sensor is located on or near the exhaust manifold, specifically in front of the catalytic converter. The P1133 code indicates the sensor is not switching properly between rich and lean engine conditions — testing with a digital multimeter (DVOM) is not effective for diagnosing this issue. Always ensure you install a high-quality replacement part. You'll need an O2 sensor socket, which is available at most auto parts stores.