P0157
System
Powertrain (Fuel/Air)
Scanner required
Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)

Understand P0157, common causes, and the right TOPDON scanner to diagnose it.

Bank 2 post-cat O2 circuit low.

Common symptoms

  • Failed smog test
  • Check engine light

Typical causes

  • Short in O2 circuit
  • Failed sensor
  • Connector corrosion

What scanner do you need?

Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Recommended TOPDON scanners

Frequently asked questions

Can I diagnose P0157 with a basic code reader?
P0157 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with P0157?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.