P0155 code meaning
O2 Sensor Heater Circuit Bank 2 Sensor 1
Powertrain system Generic code P01xx codes Check engine light
What P0155 means
The upstream oxygen sensor on bank 2 (sensor 1) has its own electric heater. 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.
P0155 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.2 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0155
- Check engine light on
- Higher emissions and consumption after cold start
- Follow-up codes P0153/P0154 possible
Common causes of P0155
- Most likelyHeater element of the sensor burnt out (sensor must be replaced)
- PossibleFuse or relay of the heater supply faulty
- PossibleHeater wiring or connector open, corroded or shorted
- Less likelyHeater driver in the control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor heater bank2 sensor1Oxygen sensor heater circuitFuses
What each part of P0155 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 55 | The exact fault in that area. |
What to do next
- Note P0155 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0155
What does P0155 mean?
P0155 means "O2 Sensor Heater Circuit Bank 2 Sensor 1". The upstream oxygen sensor on bank 2 (sensor 1) has its own electric heater. It is a generic code, so it means the same on every make.
Is it safe to drive with P0155?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0155 fail an emissions test?
Yes, it can. P0155 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0155 to fix?
Difficulty: medium. A typical repair takes 0.2 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0155 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.