Error code

OBD2 P0170

OBD2P0170
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Fuel Trim.

Severity

moderateCan drive, but symptoms may worsen over time and cause additional damage.

Summary

P0170 indicates a malfunction in the fuel trim (adjustment of air/fuel mixture) for engine bank 1. This code is common on European vehicles, especially those with high oil consumption rates.

Symptoms

  • Reduced fuel economy
  • Hard starting
  • Misfiring, rough idling, and poor acceleration
  • Visible black smoke from the tailpipe
  • Hesitation upon acceleration
  • Engine may shut off immediately after start-up

Common Causes

  • Oil contamination of the MAF sensor element
  • Defective Mass Airflow Sensor (MAF)
  • Faulty oxygen sensors
  • Vacuum leaks allowing unmetered air to enter the engine
  • High or low fuel pressure issues
  • Clogged catalytic converter

Diagnosis

  1. Check and clean the MAF sensor element if oil contamination is suspected.
  2. Inspect all associated wiring for damage or corrosion.
  3. Test oxygen sensors and their control circuits.
  4. Verify fuel pressure within specifications.
  5. Clear codes and retest after repairs to ensure resolution.

Fixes

  • Clean the MAF sensor element with an approved solvent if oil contamination is present.
  • Replace faulty oxygen sensors or their control circuits as needed.

FAQ

Why does P0170 occur more often on European vehicles?

European vehicles, especially those with high oil consumption rates like BMW, Audi, and Mercedes-Benz, are prone to this code due to issues like MAF sensor contamination from engine oil.

What should I do if cleaning the MAF sensor doesn't fix P0170?

Inspect other components such as oxygen sensors, wiring, fuel pressure regulators, and catalytic converters for any faults or issues.

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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