Downstream sensor voltage too high.
P0138 — also written PO138, P 0138, 0138 — is the OBD-II code for o2 sensor high voltage (bank 1 sensor 2). Same code, same fix: this page covers every spelling of it.
P0138 is a sensors fault code, typically costing £80–£800 to put right in a UK garage.
What causes P0138?
- Sensor failure
- Cat fault
How P0138 is fixed
- Sensor swap
- Cat inspection
P0138 repair cost in the UK
Most P0138 repairs land between £80–£800 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P0138?
Drivable.
Urgency: low.