2004 Nissan 350Z O2 Sensor Circuit High (P0152/P0132) - Fix & Diagnosis Guide

What are the exact fault codes? Sometimes generic explanations differ from manufacturer-specific diagnostics. Check the actual O2 sensor voltage readings using live data. Try introducing a vacuum leak (e.g., disconnecting the PCV hose) and observe if the sensor voltage drops — this can help identify whether the issue is due to a rich mixture or an electrical short. Are you using a scanner with live data capabilities? If so, monitor real-time O2 sensor voltages and fuel trims for more accurate diagnosis.

Hi Kev, Thank you for the reply. The codes I received are P0152 and P0132. I'm using an Aurolink AL-319 scanner. In Dubai, catalytic converters aren't legally required — when my previous cat failed, a mechanic simply removed it, which caused multiple issues. I’m planning to replace both front and rear O2 sensors (Bank 1 and Bank 2), but these parts are costly from dealerships. I’ve had to order American-made sensors via international shipping due to availability. I expect that installing the new catalytic converter will resolve the issue, but I'm worried about whether the 'O2 Sensor Circuit High' codes (P0152) could damage the new cat or cause future problems. Is there any additional diagnostic step I can take with my AL-319 scanner to get more insight into what’s happening? Many thanks, Andrew

Let's focus on the O2 sensor codes before addressing the catalytic converter. For P0152 (O2 Sensor Circuit High, Bank 2 Sensor 1) and P0132 (O2 Sensor Circuit Low, Bank 1 Sensor 1): - The PCM detects higher-than-expected voltage from the O2 sensor. - Possible causes: a rich fuel mixture or an electrical short in the sensor wiring. - For Bank 1 Sensor 1: likely R/Y wire - For Bank 2 Sensor 1: likely L/G wire It's unlikely both sensors failed simultaneously due to electrical faults. First, use your scanner to check real-time O2 sensor voltages. Then, simulate a vacuum leak (e.g., disconnect the PCV hose) and observe if the voltage drops — this can help determine whether it’s a fuel mixture or wiring issue. Also, review Fuel Trims (FTs). Check Short-Term and Long-Term Fuel Trim values to identify if there's an underlying rich condition. If STFT is high (e.g., +25%), that suggests a vacuum leak or fuel pressure problem. Note: In some cases, measuring voltage directly at the sensor wire may be necessary — but start with live data from your scanner first.

Hi Kev, I just started my car at idle and recorded several parameters. The values fluctuated slightly as the engine idled. DTC: P0152 Fuel System Control (CL): Normal Load %: 34.1% ECT: 90°C STFT Bank 1: +22%, Bank 2: +25% LTFT Bank 1 & 2: 0% RPM: 825 Spark Advance: 15.0° IAT: 43°C MAF: 4.53 g/s TP%: 0% O2 B1S1 (V): 0.0 V STFT B1S1: 3%-20% O2 B1S2 (V): 0.340 V STFT B1S2: N/A O2 B2S1 (V): 0.840 V STFT B2S1: -18.8% O2 B2S2 (V): 0.340 V STFT B2S2: 99.2% OBDSUP: OBD11 I’m not sure what all these readings mean, but I started the car and let it idle without driving. Any additional data or interpretation you’d recommend? Many thanks for your help! Andrew

Did you disconnect the battery at any point? A zero voltage reading on B1S1 (Bank 1 Sensor 1) is concerning. The STFT values are high (+22% and +25%) while LTFT remains near zero — this strongly suggests a vacuum leak or fuel pressure issue. B1S1 showing 0.0 V is abnormal; it should typically be between 0.1–0.9 V during idle. B2S1 at 0.840 V indicates a rich condition, which may point to an underlying fuel delivery or vacuum leak problem.

Thanks Kev! I’ll have my mechanic inspect the system once the catalytic converter arrives. I’ve noticed that the car sometimes accelerates on its own while driving — this could be due to erratic fuel pressure or a vacuum leak. I originally thought it was caused by removing the cat and having no downstream O2 sensor readings, leading to incorrect rich/lean signals. I’ll have them check for vacuum leaks and verify fuel pressure before any further work. I’ll update you in about two weeks with the results. Many thanks again for your guidance! Andrew