Error code

OBD2 P0173

OBD2P0173
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Fuel Trim.

Severity

moderateCan be driven, but performance may suffer. Addressing the issue is recommended.

Summary

P0173 indicates a malfunction in the long-term fuel trim for engine bank 2. This code is often related to issues with the Mass Airflow Sensor (MAF) on European vehicles due to oil contamination.

Symptoms

  • Reduced fuel economy
  • Hard starting
  • Misfiring, rough idling, and poor acceleration
  • Visible black smoke from tailpipe
  • Hesitation upon acceleration

Common Causes

  • Oil contamination of the MAF sensor element
  • Defective or fouled oxygen sensors
  • Use of fuel and oil additives with silicone compounds
  • High or low fuel pressure issues
  • Vacuum leaks allowing unmetered air to enter the engine

Diagnosis

  1. Record all codes and freeze frame data.
  2. Inspect and clean the MAF sensor element if applicable.
  3. Test the operation of the MAF sensor with a scanner.
  4. Check oxygen sensors for resistance, reference voltage, continuity, and ground issues.
  5. Verify fuel pressure is within specifications.

Fixes

  • Clean or replace the Mass Airflow Sensor (MAF) if contaminated by oil.

FAQ

What does P0173 mean?

P0173 indicates a malfunction in the long-term fuel trim for engine bank 2, often due to issues with the Mass Airflow Sensor (MAF) on European vehicles.

How do I fix P0173?

Clean or replace the MAF sensor if contaminated by oil. Check and clean oxygen sensors, verify fuel pressure is within specifications.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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