97 VW Jetta P0422 and P0440 Codes: Causes and Solutions After Front O2 Sensor Replacement
I recently replaced the front oxygen sensor on my 1997 VW Jetta with 170,000 miles. Since the replacement, my fuel efficiency has remained strong at around 30 mpg, but I've noticed that the engine sometimes drops RPMs significantly while idling and nearly stalls. What should I be checking for when diagnosing P0422 and P0440 codes? Could an incorrect torque setting on the new O2 sensor be contributing to these fault codes?
Replacing only the front oxygen sensor without also replacing the one located behind the exhaust converter often triggers P0422 and P0440 codes. It's important to ensure both sensors are properly addressed for accurate emissions control and code clearance.