Air Flow Sensor Terminal Identification Second Design Sensor

Constant Control

Regulated 5 volt reference


Voltage Signal

Signal voltage representing air flow


Earth Ground

Sensor ground return

The air flow meter and ECU are wired as shown in the diagram; signal characteristics are depicted by the accompanying graph. The use of a regulated 5 volt reference eliminates the need for the VB terminal with this sensor circuit.

Resistors R1 and R2 provide self diagnostic capabilities and allow for a fail-safe voltage at the ECU in the event of an open circuit. These two resistors have a very high resistance value (relative to r1 and r2) and essentially have no electrical effect on the circuit under normal operating conditions. They will, however, affect the open circuit voltage measured on the Vs wire at the ECU.

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