Fuel and air

P00BC — Mass Air Flow (MAF) Sensor "A" Range/Performance – Air Flow Too Low

Severity: medium Drive with care, to a shop

What P00BC means

The engine control module compares the reading from mass air flow (MAF) sensor "A" with the airflow it expects based on engine speed, throttle position and load. When the measured airflow is clearly lower than expected, it stores P00BC. The cause can be the sensor or its circuit, or a real problem with air moving through the intake.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Reduced power or hesitation
  • Higher fuel consumption
  • Hard starting or stalling
  • Abnormal fuel trim values

Possible causes

  1. Dirty or contaminated MAF sensor element
  2. Intake air leak or vacuum leak
  3. Failed or failing MAF sensor
  4. Damaged wiring or corroded connector at the MAF sensor
  5. Clogged air filter or restricted intake duct
  6. Rarely, ECM software or calibration issue

How to diagnose

  1. Read stored codes and freeze frame data and look for related intake, throttle or fuel trim codes
  2. Inspect the air filter, intake ducting, boots and clamps, especially downstream of the sensor
  3. Check the MAF connector and harness for corrosion, damage, power and ground
  4. Compare live MAF airflow at idle and under load with the expected values for the engine
  5. Review short and long term fuel trims: a large positive value suggests a leak or under-reading sensor
  6. Smoke test the intake and check vacuum lines for leaks
  7. Clean the sensor with dedicated MAF cleaner and see if readings change
  8. If still unsure, compare with a known good MAF sensor

Common fixes

  • Replace the air filter
  • Clean the MAF sensor with dedicated cleaner
  • Replace cracked intake hoses, boots or clamps
  • Repair the wiring or connector
  • Replace the MAF sensor
  • Update ECM software if the manufacturer has a fix

Questions and answers

Can I drive with P00BC?

Briefly and carefully, to get it diagnosed. The engine may run rough, lose power or stall, and fuel economy will suffer.

Will cleaning the MAF sensor fix P00BC?

It can, if contamination is the cause. Check the air filter and look for intake leaks first, or the code will likely return.

What most often causes P00BC?

A dirty MAF sensor and intake air leaks are the most common. A failed sensor, wiring faults or a clogged filter are less frequent.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.