2001 Chrysler 300M P0140 and P0161 O2 Sensor Codes: Wiring Issue Diagnosis and Smog Readiness Fix
Hi there, I recently noticed my check engine light is on in my 2001 Chrysler 300M with a 3.5L V6 engine (approximately 82,500 miles). A diagnostic scan revealed two trouble codes: P0140 (O2 sensor circuit no activity detected — Bank 1 Sensor 2) and P0161 (O2 sensor heater circuit — Bank -2 Sensor 2). The car was involved in a minor accident over a year ago, which coincided with the first appearance of intermittent check engine light issues. Based on this history, I suspect the problem may lie in the electrical circuit—such as connectors, fuses, or wiring—rather than faulty oxygen sensors. I’d like to understand how to accurately diagnose and resolve this issue. Specifically: What steps should I take to identify whether it’s a wiring fault or sensor failure? And where are these two O2 sensors physically located in the 2001 Chrysler 300M? Thank you for any guidance!
While the accident might have contributed to a wiring fault, it's not uncommon for older 2001-era Chrysler vehicles with over 80k miles to experience multiple O2 sensor issues. The P0140 code refers to the upstream O2 sensor in Bank 1, and P0161 relates to the downstream heater circuit in Bank 2. To determine which bank corresponds to cylinder #1, check the wiring harness sticker that labels injector or coil numbers—cylinder #1 side is typically Bank 1. Some 2001 Chrysler 300M models require a software update for accurate O2 sensor code interpretation. My recommendation: replace the upstream O2 sensor first with a dealer-part, clear the codes, then drive the vehicle to see if the issue returns before investing in the downstream sensor replacement.