Possible causes

– Faulty HO2S Bank 1 Sensor 2
– HO2S Bank 1 Sensor 2 harness is open or shorted
– HO2S Bank 1 Sensor 2 circuit poor electrical connection

When is the code detected?

The test fails if the Powertrain Control Module (PCM) does not detect the output of the HO2S in a calibrated amount of time.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1138 FORD Description

Sensor Indicates Lean The downstream HO2S sensors are forced rich and lean and monitored by the Powertrain Control Module (PCM)

FORD Technical Service Bulletins for P1138 code