| DTC Data Sheet | |
| System | Powertrain |
| Standard | SAE J2012 / ISO 15031-6 |
| Fault type | Performance |
| Official meaning | O2 Sensor Circuit Slow Response (Bank 2, Sensor 2) |
Bank 2 downstream O2 sensor responds too slowly to mixture changes. Aged sensor or contamination.
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P0159 Quick Answer
Bank 2 downstream O2 sensor responds too slowly to mixture changes. Aged sensor or contamination.
What Does P0159 Mean?
O2 Sensor Circuit Slow Response (Bank 2, Sensor 2). Bank 2 downstream O2 sensor responds too slowly to mixture changes. Aged sensor or contamination.
Symptoms
- Check engine light
- Catalyst monitor slow to run
Common Causes
- Aged O2 sensor
- Contamination (silicone gasket sealer, coolant, oil)
- Marginal heater operation
Diagnosis Steps
You’ll need a scan tool capable of reading live powertrain data, a digital multimeter, and access to the wiring diagram for the specific platform.
- Graph bank 2 downstream voltage during a forced rich-lean transition (snap-throttle, then steady cruise). Slow recovery confirms slow response.
- Compare to bank 1 downstream sensor.
Possible Fixes
- Bank 2 downstream O2 sensor replacement
- Repair contamination source
Can I Still Drive With P0159?
The vehicle will usually still drive with P0159 stored, but performance, drivability, or emissions will be degraded. The PCM may inhibit emissions monitors and limit closed-loop fueling adjustments. Drive to a workshop, but don’t ignore the code long-term — degraded sensor data can mask other faults and shorten catalyst life.
How Serious Is This Code?
P0159 is a moderate-priority fault. It will not prevent the engine from running but unaddressed it can damage the catalytic converter, reduce fuel economy, or cause failed emissions testing. Address within a few drive cycles.
Brand-Specific Guides for P0159
Manufacturer-specific diagnostic procedures with factory data and pin-level details for vehicles where this code commonly sets:
FAQ
Will P0159 clear itself?
Only if the underlying fault was intermittent and self-corrected. Most root causes are persistent and require physical repair.
Can I clear P0159 without fixing it?
You can clear it with a scan tool, but it will return as soon as the fault condition reappears — typically within one or two drive cycles.
Is P0159 related to other codes?
Often, yes. Adjacent codes in the same circuit or system frequently set together — if P0159 is present, scan for related codes and address them as a group.