P0102 medium Severity

P0102: Mass Air Flow (MAF) Sensor Circuit Low Input

The engine may idle rough, run inefficiently, hesitate on acceleration, or stall, and fuel economy can decrease.

Overview

P0102 indicates the Engine Control Module detected a low-voltage signal from the Mass Air Flow sensor circuit, often caused by sensor faults, wiring issues, air leaks, or airflow restrictions.

Common Symptoms

  • Check Engine Light illuminated
  • Rough or uneven engine idle
  • Poor acceleration or hesitation
  • Reduced fuel efficiency
  • Hard starting or stalling

Most Common Causes

Contaminated or dirty MAF sensor high

Dirt, oil, or debris on the MAF sensing element can lower the output signal.

Faulty MAF sensor high

Internal failure of the sensor itself leading to low voltage readings.

Wiring harness issues (open/short/poor connection) high

Damaged electrical connections between the MAF and ECM can cause low signal.

Air intake restriction or leaks medium

Intake leaks downstream of the MAF or clogged filters may affect readings.

Faulty engine control module (ECM) low

Rare but possible that ECM misreads the MAF input.

Diagnostic Steps

  1. Use an OBD-II scanner to confirm P0102 and check for related codes.
    Expected: Code P0102 present with no other unrelated codes.
    Interpretation: Validates that the MAF circuit is reporting low input.
  2. Visually inspect MAF sensor and wiring harness for damage or contamination.
    Expected: No frayed wires, corrosion, or debris on sensor.
    Interpretation: Physical damage or contamination can explain low signal.
  3. Check and clean the MAF sensor with approved cleaner.
    Expected: Cleaner removes grime; sensor looks free of deposits.
    Interpretation: Cleaning often restores correct signal range.
  4. Test MAF output voltage with a multimeter under various engine loads.
    Expected: Voltage within manufacturer spec for idle and higher RPM.
    Interpretation: Abnormal low values point to sensor or circuit fault.
  5. Inspect intake system and replace air filter if dirty; check for leaks.
    Expected: No leaks or restrictions; filter is clean.
    Interpretation: Airflow issues can distort MAF readings.
  6. If sensor and wiring are good, consider ECM testing or replacement.
    Expected: ECM provides stable readings.
    Interpretation: Eliminates rare control unit faults.

Repair Solutions

Clean MAF sensor easy
Estimated Cost: $10 - $30

Cleaning with appropriate MAF cleaner often resolves low input signals.

Repair wiring/connectors medium
Estimated Cost: $20 - $150

Includes fixing shorts, opens, corrosion, or poor pins.

Replace MAF sensor medium
Estimated Cost: $90 - $400

OEM sensor recommended for accurate readings.

Fix air intake leaks or replace filter easy
Estimated Cost: $15 - $100

Ensures accurate airflow measurement.

ECM repair or replacement hard
Estimated Cost: $500 - $1500

Uncommon; only if confirmed defective.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing only the MAF sensor when the actual issue is wiring or air leaks
  • Attributing rough running solely to engine mechanical issues without checking airflow
  • Misreading vacuum leaks as a bad MAF sensor

Frequently Asked Questions

What does a P0102 diagnostic trouble code signify?

The P0102 code stands for Mass Air Flow (MAF) Sensor Circuit Low Input. This generally indicates an issue with the Air Intake system.

Reflecting on severity: How bad is P0102?

The P0102 code is considered medium severity. The engine may idle rough, run inefficiently, hesitate on acceleration, or stall, and fuel economy can decrease.

What are the symptoms of P0102?

Common symptoms include: Check Engine Light illuminated, Rough or uneven engine idle, Poor acceleration or hesitation. You might also notice the Check Engine Light is on.

Common triggers for the P0102 error

The most common causes are: Contaminated or dirty MAF sensor, Faulty MAF sensor, Wiring harness issues (open/short/poor connection).

Repair cost breakdown for P0102

The cost varies significantly based on the root cause. For example, replacing a Clean MAF sensor typically costs between $10 and $30, while fixing a ECM repair or replacement can range from $500 to $1500.

Is the P0102 code specific to BMW?

This is a universal code. You might see P0102 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

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