Code result
P0134
O2 Sensor Circuit No Activity Detected
Moderate severity
What it means
The ECU detects that the upstream oxygen sensor on bank 1 shows no switching activity or responds too slowly to changing exhaust gas composition. Often the sensor is aged, contaminated by silicone or fuel additives, or the heater circuit is degraded.
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
Sensor aged or poisoned (silicone, lead, coolant)
highOne of the most commonly reported causes for this code — check this first.
Sensor heater circuit weak
mediumA plausible cause — test and verify before replacing parts.
Exhaust leak upstream of sensor diluting reading
mediumA plausible cause — test and verify before replacing parts.
Related help
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