Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information

Condition




Diagnostic trouble code (DTC) EFI-121 is stored if the mass air flow (MAF) sensor circuit is short-circuited to ground / voltage or if there is an open-circuit in the circuit that the control module interprets as a fault.

Substitute value
- Initial boost pressure.
- Throttle position and engine speed (RPM) are used to calculate mass air flow.
- DSA is disabled.

Possible source

Signal too high:
- Short-circuit to supply voltage in the signal cable.
- Open-circuit in the ground lead.
- Faulty mass air flow (MAF) sensor.
- Faulty turbocharger (TC) control system (boost pressure too high).

Signal too low:
- Short-circuit to ground in signal cable
- Open-circuit in the signal cable or the power supply.
- Faulty mass air flow (MAF) sensor.

Fault symptom[s]
- Engine cooling fan (FC) continues operating for 10 minutes.