Code result
P0139
O2 Sensor Circuit Slow Response
Moderate severity
What it means
The ECU detects that the downstream oxygen sensor on bank 1 reports an abnormally high voltage signal, suggesting a persistently rich exhaust condition past the catalyst, a shorted sensor, or wiring shorted to a voltage source.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Engine running rich (leaking injector, high fuel pressure)
highOne of the most commonly reported causes for this code — check this first.
Sensor signal wire shorted to voltage
mediumA plausible cause — test and verify before replacing parts.
Downstream O2 sensor failed
mediumA plausible cause — test and verify before replacing parts.
Related help
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