Description
The mass air flow (maf) meter is a sensor that measures the amount of air flowing through the throttle valve.
The ecm uses this information to determine the fuel injection time and to provide the appropriate air-fuel ratio.
Inside the maf meter, there is a heated platinum wire which is exposed to the flow of intake air.
By applying a specific electrical current to the wire, the ecm heats it to a given temperature. The flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ecm varies the voltage applied to these components in the maf meter. The voltage level is proportional to the airflow through the sensor, and the ecm uses it to calculate the intake air volume.
The circuit is constructed so that the platinum hot wire and the temperature sensor create a bridge circuit, and the power transistor is controlled so that the potentials of a and b remain equal to maintain the predetermined temperature.
Hint:
When any of these dtcs are set, the ecm enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ecm, according to the engine rpm and throttle valve position. Fail-safe mode continues until a pass condition is detected.
Hint:
When any of these dtcs are set, check the air-flow rate by selecting the following menu items on the intelligent tester: diagnosis / enhanced obd ii/ data list / primary / maf.
Monitor description
If there is a defect in the maf meter or an open or short circuit, the voltage level deviates from the normal operating range. The ecm interprets this deviation as a malfunction in the maf meter and sets a dtc.
Example: when the sensor output voltage remains less than 0.2 V, or more than 4.9 V, for more than 3 seconds, the ecm sets a dtc.
If the malfunction is not repaired successfully, a dtc is set 3 seconds after the engine is next started.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Component operating range
Wiring diagram
Inspection procedure
Hint:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. 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.
Result
Hint:
*1: The value must change when the throttle valve is
open or closed with the engine running.
Standard voltage
Standard voltage
Standard resistance (check for open)
Standard resistance (check for short)
Check harness and connector (mass air flow meter - integration relay)
Standard resistance (check for open)
Standard resistance (check for short)
Standard resistance (check for open)
Standard resistance (check for short)
Brake Hold
The brake hold system
keeps the brake applied
when the shift lever is in D,
S or N with the system on
and the brake pedal has
been depressed to stop the
vehicle. The system
releases the brake when the
accelerator pedal is
depressed with the shift
lever in D or S to allow
smooth start off.
Enabling t ...
Spiral cable
Components
Removal
Caution:
Be sure to read the precautionary notices concerning the
srs airbag system before servicing it (see page rs-1).
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery ...
Evaporative emission system reference orifice
Dtc summary
Hint:
The reference orifice is located inside the canister pump module.
Description
The description can be found in the evap (evaporative emission) system (see
page es-335).
Inspection procedure
Refer to the evap system (see page es-340).
Monitor description
5 Hours* af ...