P1146

What it means

P1146 on a Volkswagen means the engine control unit has found a fault in the power supply to the mass air flow (MAF) sensor circuit. The control unit monitors the supply voltage to the sensor, and the code sets when that voltage is missing, too low or outside the expected range. Without a reliable airflow signal the engine management falls back on a default air mass value.

Symptoms

• Engine warning light on
• Poor or hesitant acceleration
• Reduced power, possibly with the engine in limp-home mode
• Rough or unstable idle
• Hard starting or occasional stalling
• Higher than normal fuel consumption

Possible causes

• Damaged, corroded or loose connector at the MAF sensorlikely
• Wiring fault in the sensor supply or earth wire (open circuit, short or high resistance)likely
• Faulty MAF sensor with an internal fault affecting its supplypossible
• Fault in the supply relay or fuse feeding the sensor, where fitted (depends on model and engine)possible
• Poor earth connection or low system voltage from a weak battery or charging faultpossible
• Fault inside the engine control unitrare

How to diagnose

1. Read all stored fault codes and freeze frame data, noting any other codes for air flow, throttle or system voltage, then check for related technical service information for the model and engine.
2. Check the battery condition and charging voltage, as low system voltage can set supply faults.
3. Visually inspect the MAF sensor connector and wiring for chafing, corrosion, bent pins, oil contamination or loose terminals.
4. View the live MAF reading and air mass value with the engine at idle and while revving, and compare with expected values for the engine.
5. With the connector unplugged and ignition on, measure the supply voltage and earth at the harness side against the wiring diagram for that model.
6. Check the relevant fuses and relay, if fitted, and test the supply wire for voltage drop under load.
7. Test the wiring between the sensor and the control unit for continuity and for shorts to earth or to supply.
8. If the wiring and supply are good, substitute a known good sensor or test the sensor to confirm it is at fault before suspecting the control unit.

How to fix

• Clean, repair or replace the damaged MAF connector or terminals.
• Repair or replace the faulty wiring in the supply or earth circuit.
• Replace the MAF sensor if it is confirmed faulty.
• Replace the faulty fuse or relay and find out why it failed.
• Correct the battery or charging system fault, and clean or repair poor earth connections.
• Repair or replace the engine control unit only after all other causes are ruled out and the fault is confirmed.

Can I keep driving?

This code for other makes

• P1146SubaruPressure Sensor Circuit Range Performance Problem High Input

Nearby codes

• P1145VolkswagenMass Or Volume Air Flow Circuit Short To B+
• P1147VolkswagenOxygen Sensor Control Bank 2 System Too Lean