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P1109 Manufacturer-specific Basic entry

MAF Ground Malfunction

Updated 2026-10-10 · Manufacturer-specific powertrain

Severity
Medium
Typical repair cost
40 – 350 EUR
System
Powertrain

This is a manufacturer-specific code. Its exact meaning can differ between makes; the definition below follows the most common usage.

What it means

P1109 is a general fault for the MAF Ground circuit: the engine control module has detected a condition it cannot classify as low, high or open, often because the fault changes during the test.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Check engine light on
  • Rough or unstable idle
  • Hesitation or poor acceleration
  • Increased fuel consumption
  • Possible limp mode with reduced power

Common causes

  1. Damaged, chafed or corroded wiring in the MAF Ground circuit
  2. Corroded, loose or water-damaged connector terminals
  3. Failed MAF Ground component (sensor, solenoid or actuator)
  4. Poor ground connection for the module or component
  5. Faulty control module driver (rare, confirm all else first)

How to diagnose

  1. Read freeze frame data and note when the code set (cold start, under load, after rain)
  2. Inspect the MAF Ground connector for bent pins, corrosion and water; wiggle the harness with the engine running and watch live data
  3. Measure supply voltage and ground at the connector with the key on
  4. Check the signal wire for shorts to ground or battery and for continuity to the control module
  5. Test or substitute the MAF Ground only after wiring and connectors are confirmed good
  6. Clear the code and complete a drive cycle to confirm the repair

Frequently asked questions

Can I keep driving with P1109?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing P1109 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

P1107P1108P1110P1111

Nearby codes in this group