COMPONENT LOCATION |
GENERAL DESCRIPTION |
The Mass Air Flow Sensor (MAFS) is located between the air cleaner assembly and the throttle body. The MAFS uses a hot film type sensing element to measure the mass of intake air entering the engine. This hot film type air flow sensor consists of a hot film sensor, housing and metering ducts. Mass air flow rate is measured by detection of heat transfer from a hot film probe. The change in air flow rate causes change in the amount of heat being transferred from the hot film probe surface to the air. A large amount of intake air represents acceleration or high load conditions while a small amount of intake air represents deceleration or idle. The mass of intake air should increase at acceleration and be stable during constant engine speed. The ECM uses this information to determine the injection duration and ignition timing for the desired air/fuel ratio.
DTC DESCRIPTION |
The ECM compares the airmeter input frequency to low and high limits. When the frequency is outside the allowable limits, the circuit is determined to be failed. If ECM detects that frequency signal of MAFS is higher thatn 11900Hz for more than 75 second failure during 125 second dignostic test while enable condition is met, ECM determines that a fault exists and a DTC is stored.MIL(Malfunction Indicatin Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC DETECTING CONDITION |
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Compares the airmeter input frequency to a high limit | ● Noise ● MAFS ● ECM | |||||
Enable Conditions | ● Engine Speed ≥ 500 rpm ● Engine Running Time ≥ 5 second ● Ignition Voltage ≥ 11V | ||||||
Threshold value | ● MAF frequency signal > 11900Hz | ||||||
Diagnosis Time | ● Continuous (More than 75 second failure for every 125 second tests ) | ||||||
MIL On Condition | ● 2 Driving Cycles |
SPECIFICATION |
Air Flow (kg/h) | Frequency (Hz) | Air Flow (kg/h) | Frequency (Hz) | Air Flow (kg/h) | Frequency (Hz) |
0 kg/h | 720 ~ 880Hz | 43.2 kg/h | 3,975Hz | 270.0 kg/h | 7,219Hz |
12.6 kg/h | 2,595Hz | 57.6 kg/h | 4,361Hz | 360.0 kg/h | 7,945Hz |
18.0 kg/h | 2,930Hz | 72.0 kg/h | 4,683Hz | 486.0 kg/h | 8,736Hz |
23.4 kg/h | 3,208Hz | 108.0 kg/h | 5,362Hz | 666.0 kg/h | 9,660Hz |
32.4 kg/h | 3,609Hz | 198.0 kg/h | 6,527Hz | 900.0 kg/h | 10,613Hz |
SCHEMATIC DIAGRAM |
TERMINAL AND CONNECTOR INSPECTION |
1. | Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage. |
2. | Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. |
3. | Has a problem been found? YES ▶ Repair or replace if necessary NO ▶ Go to “Ground Circuit Inspection” procedure. |
GROUND CIRCUIT INSPECTION |
1. | IG “OFF” |
2. | Disconnector MAFS connector. |
3. | Measure the voltage between terminal 1 of MAFS harness connector. |
4. | Measure the voltage between terminal 1 and 3 of MAFS harness connector.
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5. | Is the measured voltage within the specification? YES ▶ Go to “Component Inspection”. NO ▶ After repairing or replacing contact resistance in ground circuit and open in the MAFS circuit |