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Home >> Chevrolet >> 2018 >> Trax Premier, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 10 (Engine Controls And Fuel - 1.4L (LE2) - Diagnostic Information And Procedures (P0325-P2635) And Symptoms) >> Diagnostic Information and Procedures >> DTC P121A >> Circuit/System Description

Circuit/System Description

WARNING: This page is about a different car, the 2018 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.

The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A large quantity of air entering the engine indicates a high load condition.

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore.

The MAF sensor is supplied power through the powertrain relay and a fuse. The ECM enables the MAF sensor only during engine run mode by grounding the MAF control circuit via a solid state devise called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM monitors the status of the driver. If the ECM detects an incorrect voltage for the commanded state of the driver, a MAF sensor supply voltage low side driver control circuit DTC is set.

The sensors listed below are integrated within the mass air flow/multifunction intake air sensor:

The sensors listed below share an ECM supplied 5 V reference circuit:

The sensors listed below share an ECM supplied low reference circuit:

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