OBD-II Code · Sensors
P0155
O2 Sensor Heater Circuit (B2S1)
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$150–$350
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Bank 2 upstream heater failure.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Likely causes
- Failed heaterMost common
- Fuse
- Wiring
Read the full diagnostic procedureP0155 is a heater-circuit fault on bank 2 upstream — bank-2 mirror of P0135.
P0155 is a heater-circuit fault on bank 2 upstream — bank-2 mirror of P0135.
Heater current draw outside spec window
open, shorted, or implausible. Ohm the heater pins (6-15Ω cold narrow-band, 2-4Ω wideband); open = sensor heater coil failed (replace sensor). Verify B+ at heater feed pin and pulsed ground at heater control pin from the ECU. Frequently sets together with P0135 (bank 1) when both sensors are the same age and a shared O2 heater fuse blows — check the fuse before swapping parts. On longitudinal pickup trucks, bank 2 is usually passenger side; on transverse V6, bank 2 is the front bank. Verify before reaching for the sensor.
Vehicle-specific patterns2003-2008 Toyota Tundra / Sequoia 4.7L 2UZ-FE — longitudinal, bank 2 is passenger side; throws P0155 around 130k miles routinely.
- 2003-2008Toyota Tundra / Sequoia 4.7L 2UZ-FE — longitudinal, bank 2 is passenger side; throws P0155 around 130k miles routinely.
- 2005-2010Chrysler 300 / Charger 5.7L Hemi — TIPM relay failure causes simultaneous P0135 + P0155 (sensors fine; TIPM is the actual problem).
- 2007-2014Cadillac CTS / SRX 3.6L LFX — transverse, bank 2 is front; throws P0155 from connector corrosion in the road-spray zone.
- 2010-2016Audi Q5 / A4 2.0T quattro — sets P0155 from a chafed bank-2 wideband harness against the engine cradle. Cost band: $200-$500 sensor; up to $700+ if TIPM-related on Mopar; $25-$80 if just a fuse or connector.
Look up another code
P0155 — frequently asked
What does a P0155 code mean?
Bank 2 upstream heater failure.
What causes a P0155 code?
Common causes: Failed heater; Fuse; Wiring.
What are the symptoms of a P0155 code?
Typical symptoms: Check engine light.
Is it safe to drive with a P0155 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $150-$350.
How do I diagnose a P0155 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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