The P2238 diagnostic trouble code (DTC) indicates a problem with the Air/Fuel (A/F) sensor circuit range/performance bank 1 sensor 1 on a 2008 Toyota Corolla S. This article documents troubleshooting steps taken to resolve this persistent issue.
Testing Procedures and Results
Following Toyota’s recommended diagnostic procedure for the P2238 code, multiple tests were conducted using a Fluke 87 multimeter with new leads. These tests included checking voltage, resistance, and ground connections within the A/F sensor circuit. All measurements fell within the manufacturer’s specified parameters as outlined in the Toyota procedure document.
Component Replacement
Despite passing all diagnostic tests, the P2238 code persisted. Initially, a DL WIDEBAND O2 sensor from AutoZone was installed. When this failed to resolve the issue, a Denso brand O2 sensor was used, based on research suggesting potential performance differences between brands. However, the P2238 code remained. To further eliminate the sensor as the culprit, a known-good A/F sensor was borrowed from a 2003 Corolla and tested. The P2238 code persisted even with this sensor.
ECM Consideration
Toyota’s official procedure suggests ECM replacement if all other tests pass. However, consultation with an experienced Lexus technician (with 12 years of experience) advised against immediately replacing the ECM. Despite re-running the entire Toyota diagnostic procedure three times with consistent results, the P2238 code remains unresolved. All tests point to a functioning A/F sensor and associated circuitry.
Seeking Further Guidance
After exhausting standard diagnostic procedures and component replacements, the root cause of the P2238 code in this 2008 Toyota Corolla S remains elusive. Further suggestions and insights from experienced technicians are welcome. While ECM replacement is a possibility, confirming its necessity before incurring the expense is desired.
