Is It Safe to Drive With a P0155 Code?
Common Symptoms of a P0155 Fault
EML on
No significant driveability issues
Higher cold-start emissions on bank 2
Possible Causes of P0155
A P0155 code can be triggered by faults across several systems. Identifying the exact root cause requires proper diagnostic equipment and live data — not just reading the code.
O2 Heater Wiring Fault — Bank 2
Wiring to bank 2 upstream O2 heater is damaged.
Blown Fuse
Fuse protecting bank 2 O2 heater circuit.
Heater Element Failure
Bank 2 upstream O2 sensor heater element failed.
ECU Output Fault
ECU controlling bank 2 O2 heater.
Why we don't list the exact part: A P0155 code tells you what's happening but not why. Replacing parts based on the code alone is the most common way drivers waste money. A proper diagnosis identifies the specific cause first.
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P0155 and Your MOT
A stored P0155 fault code will cause your car to fail its MOT. The engine management light will be illuminated during the test — an automatic failure under current MOT standards. Even if the light temporarily clears, the code remains in ECU memory and can be read by testers.
Get the fault diagnosed and repaired first, then have the code cleared and confirm the light stays off before booking your MOT.