P0155: O2 Sensor Heater Circuit (Bank 2 Sensor 1)
The heater inside the upstream oxygen sensor on bank 2 is not working.
What P0155 means
P0155 is the bank 2 upstream version of the heater code P0135. Every modern oxygen sensor has a heater so it reaches working temperature soon after starting, which lets the computer switch to precise fuel control sooner. The engine computer powers the heater and monitors the current it draws. P0155 sets when that current is too low, too high or missing on the bank 2 upstream sensor. A burned out heater element is the most common cause, and because the heater is built into the sensor, the fix is a new sensor. If several heater codes show up together, look for a shared fuse or power wire instead, since it is unlikely that multiple sensors failed at once. KBB notes that heater codes can cause poor fuel economy and carbon build up over time. Shops measure the heater resistance, check the fuse and power feed, and confirm the ground before replacing anything.
Common symptoms
- Check engine light on
- Slightly worse fuel economy after cold starts
- Higher emissions
- Possible rough running when cold
- Usually no other symptoms
Most common causes
- Burned out heater element in the bank 2 upstream sensor
- Blown oxygen sensor heater fuse
- Open or shorted heater wiring
- Corroded connector
- Engine computer heater control fault (rare)
What to check yourself first
Check the oxygen sensor heater fuse. If P0135 is also present, both upstream heaters may share a fuse or power feed. Measure heater resistance at the sensor connector with a meter.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace oxygen sensor | $440-$523 | Replacing the sensor is the normal fix for a dead heater. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For a fuse, relay or wiring fault, especially if more than one heater code is set. |
| Check engine light diagnosis at a shop | $125-$183 | Confirms the heater failure before parts are bought. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0135 O2 Sensor Heater Circuit (Bank 1 Sensor 1)
- P0150 O2 Sensor Circuit (Bank 2 Sensor 1)
- P0161 O2 Sensor Heater Circuit (Bank 2 Sensor 2)
- P0141 O2 Sensor Heater Circuit (Bank 1 Sensor 2)
- P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)