EngineLightCodes
Powertrain code

P0155 O2 Sensor Heater Circuit Bank 2 Sensor 1

Severity
Fix soon
Typical repair cost
$10–$330
Do it yourself
Possible, medium
Shop time
0.2–2 hours

The upstream oxygen sensor on bank 2 (sensor 1) has its own electric heater.

How the engine computer detects it

P0155 is the bank 2 counterpart of P0135: the heater current is outside its window or the driver voltage does not follow the command. GM fails it outside 0.3–3.1 A (8 s or 8 of 10 samples, two trips); Ford outside roughly 0.22–0.465 A minimum to 3 A, with related codes for heater temperature control (P0050) and resistance (P0059). Closed loop on bank 2 then starts late after a cold start, and the sensor checks are suspended. P0135 together with P0155 points to a shared supply or fuse.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light on
  • Higher emissions and consumption after cold start
  • Follow-up codes P0153/P0154 possible

Common causes

  1. Heater element of the sensor burnt out (sensor must be replaced) Most likely
  2. Fuse or relay of the heater supply faulty Possible
  3. Heater wiring or connector open, corroded or shorted Possible
  4. Heater driver in the control module faulty Less likely

How to diagnose P0155

  1. Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
  2. Inspect the parts involved: oxygen sensor heater bank2 sensor1, oxygen sensor heater circuit, fuses.
  3. Work through the causes above from most to least likely, cheapest checks first.
  4. Clear the code and drive a full drive cycle to confirm the repair held.

Reading the code

P
Powertrain
0
Generic (SAE) code
1
Fuel and air metering
55
Specific fault

Questions drivers ask

Can I drive with code P0155?

Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.

Will my car pass an emissions inspection with P0155?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0155 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0155 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.