7GR-FKS ENGINE CONTROL  SFI SYSTEM  P010012  Mass or Volume Air Flow Sensor "A" Circuit Short to Battery  P010014  Mass or Volume Air Flow Sensor "A" Circuit Short to Ground or Open  

The mass air flow meter sub-assembly is a sensor that measures the intake air volume using the following built-in components:

Intake air flows past the temperature sensor (before heater), the heater, and then the temperature sensor (after heater) of the silicon chip sensor in the by-pass duct. As the intake air is warmed up when it is exposed to the heater, the temperature of the intake air as it flows past the temperature sensor (after heater) is higher than when it flows past the temperature sensor (before heater). The difference in temperature of the intake air at each temperature sensor varies depending on the velocity of the intake air that flows past the silicon chip sensor. The temperature sensor bridge circuit detects the difference in temperature and the control circuit converts it into a pulse signal and outputs it to the ECM. When the temperature detected by the temperature sensor (before heater) is higher than that detected by the temperature sensor (after heater), backflow of the intake air is detected.

The ECM calculates the intake air volume based on the pulse signal received from the mass air flow meter sub-assembly, and uses it to determine the fuel injection duration necessary for an optimal air-fuel ratio.

The heater control bridge circuit has a temperature sensor and power transistor, and maintains the heater temperature at a specific temperature.

HINT:

When DTCs is stored, the ECM enters fail-safe mode. During fail-safe mode, the ECM calculates the fuel injection duration based on the engine speed and throttle valve angle. Fail-safe mode continues until a pass condition is detected.

5.479,1.854 6.333,2.75 6.333,2.75 6.583,2.75 true 5.917,2.906 6.333,3.417 6.333,3.417 6.583,3.417 true 5.25,2.333 4.917,2.667 4.917,2.667 4.667,2.667 true 2.688,2.083 3.083,2.333 3.083,2.333 3.333,2.333 true 3.063,2 3.25,2.083 3.25,2.083 3.5,2.083 true 2.333,1.333 2.917,1.583 2.917,1.583 3.167,1.583 true 1.417,1.583 1.667,1.583 1.667,1.583 2.094,1.417 true 1.25,2.25 1.5,2.25 1.5,2.25 1.802,2.083 true 4.667,0.583 4.917,0.75 0.25,0.167 10 false *1 6.667,2.677 6.917,2.833 0.25,0.156 10 false *a 4.5,2.583 4.75,2.75 0.25,0.167 10 false *b 3.25,1.51 3.5,1.667 0.25,0.156 10 false *c 1.25,1.5 1.5,1.667 0.25,0.167 10 false *d 3.583,2.01 3.896,2.167 0.313,0.156 10 false *e 3.417,2.26 3.729,2.417 0.313,0.156 10 false *f 1.083,2.167 1.333,2.323 0.25,0.156 10 false *g 6.667,3.344 6.917,3.5 0.25,0.156 10 false *h

*1	Mass Air Flow Meter Sub-assembly	-	-
*a	Silicon Chip Sensor	*b	By-pass Duct
*c	Heater	*d	Heater Thermistor
*e	Intake Air	*f	Temperature Sensor (After Heater)
*g	Temperature Sensor (Before Heater)	*h	Air Flow

If there is a defect or an open or short circuit in the mass air flow meter sub-assembly, the frequency level deviates from the normal operating range. The ECM interprets this deviation as a malfunction in the mass air flow meter sub-assembly circuit and stores a DTC.

Example:

When the sensor output frequency remains less than 0.1 kHz, or higher than 9.8 kHz for 3 seconds or more, the ECM stores a DTC.

HINT:

Read Freeze Frame Data using the GTS. The ECM records vehicle and driving condition information as Freeze Frame Data the moment a DTC is stored. When troubleshooting, Freeze Frame Data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.