OBD-II Fault Code

P1152: Lack Of HO2S21 Switch - Sensor Indicates Rich

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1152.

System family

Powertrain

Manufacturer-specific

Repair category

Fuel trim / rich condition

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What P1152 usually means

Lack Of HO2S21 Switch - Sensor Indicates Rich.

Common symptoms

Check Engine light; Poor drivability or reduced fuel economy depending on fault; Poor fuel economy; Fuel smell; Black smoke in severe cases

Likely causes

Leaking injector; Faulty fuel pressure regulator; Contaminated MAF/MAP reading; EVAP purge stuck open

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check fuel trims, fuel pressure, injector leak-down and purge valve operation

Repair guidance

Repair leaking injector/pressure issue, clean/replace faulty airflow sensor, repair purge system fault

Verification after repair

Clear code, road-test through the same drive condition, then rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.