OBD-II Fault Code

P1157: Lack Of HO2S22 Switch - Sensor Indicates Lean

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1157.

System family

Powertrain

Manufacturer-specific

Repair category

Fuel trim / lean 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 P1157 usually means

Lack Of HO2S22 Switch - Sensor Indicates Lean.

Common symptoms

Check Engine light; Poor drivability or reduced fuel economy depending on fault; Rough idle; Hesitation; Higher fuel trims

Likely causes

Vacuum/intake leak; Dirty or faulty MAF/MAP sensor; Low fuel pressure; Exhaust leak before O2 sensor

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check fuel trims at idle and under load; Smoke-test intake system; Inspect MAF/MAP data and fuel pressure

Repair guidance

Repair intake/vacuum leaks, clean/replace faulty sensor, correct fuel pressure or exhaust leak

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.