DTC EFI-121

1-2-1 MASS AIR FLOW SENSOR, SIGNAL





Trouble Code Conditions
- Diagnostic trouble code (DTC) EFI-121 is stored 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 unreasonable for engine speed (RPM) and throttle angle.

Substitute value(s)
- The engine control module (ECM) uses engine speed and throttle angle to determine load.
- Idle air trim adaptation disabled.
- Long-term fuel trim disabled.
- EVAP diagnostic is disabled.

Possible source(s)
Signal too high:
- Short-circuit to supply voltage in signal cable.
- Open-circuit in cable to signal or power ground.
- Defective mass air flow sensor.
- Contact resistance in terminals.

Signal too low:
- Open-circuit signal or power cable.
- Short-circuit to ground in signal cable.
- Fresh air hose damaged or loose.
- Defective mass air flow sensor.
- Contact resistance in terminals.

Fault symptom(s)
- Uneven idling and/or running.