| DTC Data Sheet | |
| System | Powertrain |
| Standard | SAE J2012 / ISO 15031-6 |
| Fault type | Circuit |
| Official meaning | O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1) |
The PCM has detected a fault in the heater circuit of the bank 2 upstream oxygen sensor. The internal heater element warms the sensor for fast light-off — without it the sensor will not switch reliably.
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P0155 Quick Answer
The PCM has detected a fault in the heater circuit of the bank 2 upstream oxygen sensor. The internal heater element warms the sensor for fast light-off — without it the sensor will not switch reliably.
What Does P0155 Mean?
O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1). The PCM has detected a fault in the heater circuit of the bank 2 upstream oxygen sensor. The internal heater element warms the sensor for fast light-off — without it the sensor will not switch reliably.
Symptoms
- Check engine light
- Reduced fuel economy after cold starts
- Slow O2 monitor readiness
- Often co-codes with P0154
Common Causes
- Failed heater element inside the sensor (most common)
- Open or shorted heater wiring
- Blown sensor heater fuse
- Connector corrosion at the sensor
- PCM driver failure (rare)
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.
- Disconnect the sensor and measure resistance across the two heater pins. Typical 4–14 ohms (verify against spec). Open or shorted reading indicates internal failure.
- Verify 12 V supply and PCM ground command at the harness.
- Check the heater fuse if multiple O2 sensors share the same circuit.
Possible Fixes
- O2 sensor replacement (heater is integral to the sensor)
- Heater circuit wiring repair
- Fuse replacement
Can I Still Drive With P0155?
The vehicle will usually still drive with P0155 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?
P0155 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 P0155
Manufacturer-specific diagnostic procedures with factory data and pin-level details for vehicles where this code commonly sets:
FAQ
Will P0155 clear itself?
Only if the underlying fault was intermittent and self-corrected. Most root causes are persistent and require physical repair.
Can I clear P0155 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 P0155 related to other codes?
Often, yes. Adjacent codes in the same circuit or system frequently set together — if P0155 is present, scan for related codes and address them as a group.