DTC 1-2-1 Mass Air Flow Sensor Signal

1-2-1 MASS AIR FLOW SENSOR SIGNAL

Preconditions for DTCs
^ If the signal from the Mass Air Flow (MAF) Sensor is lower than 0.2 Volts or greater than 2.2 Volts at idling speed, or is considered unsatisfactory according to RPM and throttle angle, this is interpreted by the control module as a fault and DTC 1-2-1 is set.

Substitute values
^ The control module uses engine speed and throttle angle to determine the load.
^ The Idle Air Control (IAC) valve's idle air trim is inhibited.
^ Long term fuel trim inhibited.
^ Only initial charge pressure is permitted.
^ The EVAP diagnosis is inhibited.

Fault sources
^ Signal too high:
- Signal lead short circuited to voltage supply.
- Break in lead to signal or power ground.
- Defective MAF sensor.
- Contact resistance in connections.

^ Signal too low:
- Break in signal or voltage lead.
- Signal lead short circuited to ground.
- Damaged or loose fresh-air hose, upper charge air cooler pipe or lower charge air cooler pipe.
- Defective MAF sensor.
- Contact resistance in connections.

Fault symptoms
^ Uneven idling and/or jerky operation.
^ Poorer performance from initial charge pressure limit.