P0174
System
Powertrain (Fuel/Air)
Scanner required
Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

System Too Lean (Bank 2)

Understand P0174, common causes, and the right TOPDON scanner to diagnose it.

Same as P0171 but detected on bank 2 of a V-engine. Often appears together with P0171 when there is a common cause like a vacuum leak or MAF issue.

Common symptoms

  • Rough idle
  • Poor acceleration
  • Often paired with P0171

Typical causes

  • Vacuum leak affecting both banks
  • MAF sensor out of range
  • Fuel delivery problem
  • Exhaust leak affecting O2 readings

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 P0174 with a basic code reader?
P0174 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 P0174?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.