MAF SEN/CIRCUIT
COMPONENT DESCRIPTION
The mass air flow sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot wire that is supplied with electric current from the ECM. The temperature of the hot wire is controlled by the ECM a certain amount. The heat generated by the hot wire is reduced as the intake air flows around it. The more air, the greater the heat loss.
Therefore, the ECM must supply more electric current to maintain the temperature of the hot wire as air flow increases. The ECM detects the air flow by means of this current change.
CONSULT REFERENCE VALUE IN DATA MONITOR MODE
Specification data are reference values.
Terminals 54 Thru 55:
ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values and are measured between each terminal and 32 (ECM ground).
ON BOARD DIAGNOSIS LOGIC
DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE
Perform "PROCEDURE FOR MALFUNCTION A" first.
If the 1st trip DTC cannot be confirmed, perform "PROCEDURE FOR MALFUNCTION 5".
If there is no problem on "PROCEDURE FOR MALFUNCTION B", perform "PROCEDURE FOR MALFUNCTION C".
If there is no problem on "PROCEDURE FOR MALFUNCTION C", perform "PROCEDURE FOR MALFUNCTION D".
NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.
PROCEDURE FOR MALFUNCTION A
With Consult
1. Turn ignition switch "ON".
2. Select "DATA MONITOR" mode with CONSULT.
3. Wait at least 6 seconds.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure".
With Generic Scan Tool
1. Turn ignition switch "ON", and wait at least 6 seconds.
2. Select "MODE 7" with GST.
3. If 1st trip DTC is detected, go to "Diagnostic Procedure".
Without Scan Tool
1. Turn ignition switch "ON", and wait at least 6 seconds.
2. Turn ignition switch "OFF", wait at least 5 seconds and then turn "ON".
3. Perform "Diagnostic Test Mode II (Self-diagnostic results)" with ECM.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure".
PROCEDURE FOR MALFUNCTION B
With Consult
1. Turn ignition switch "ON".
2. Select "DATA MONITOR" mode with CONSULT.
3. Start engine and wait 5 seconds at most.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure".
With Generic Scan Tool
1. Start engine and wait 5 seconds at most.
2. Select "MODE 7" with GST.
3. If 1st trip DTC is detected, go to "Diagnostic Procedure".
Without Scan Tools
1. Start engine and wait 5 seconds at most.
2. Turn ignition switch "OFF", wait at least 5 seconds and then turn "ON".
3. Perform "Diagnostic Test Mode II (Self-diagnostic results)" with ECM.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure".
NOTE: If 1st trip DTC is confirmed after more than 5 seconds, there may be malfunction C.
PROCEDURE FOR MALFUNCTION C
NOTE: If engine will not start or stops soon, wait at least 10 seconds with engine stopped (Ignition switch "ON") instead of running engine at idle speed.
With Consult
1. Turn ignition switch "ON".
2. Select "DATA MONITOR" mode with CONSULT.
3. Start engine and warm it up to normal operating temperature.
4. Run engine for at least 10 seconds at idle speed.
5. If 1st trip DTC is detected, go to "Diagnostic Procedure".
With Generic Scan Tool
1. Start engine and warm it up to normal operating temperature.
2. Run engine for at least 10 seconds at idle speed.
3. Select "MODE 7" with GST.
4. If 1st trip DTC is detected, go to "Diagnostic Procedure".
Without Scan Tools
1. Start engine and warm it up to normal operating temperature.
2. Run engine for at least 10 seconds at idle speed.
3. Turn ignition switch "OFF", wait at least 5 seconds and then turn "ON".
4. Perform "Diagnostic Test Mode II (Self-diagnostic results)" with ECM.
5. If 1st trip DTC is detected, go to "Diagnostic Procedure".
PROCEDURE FOR MALFUNCTION D
CAUTION: Always drive vehicle at a safe speed.
With Consult
1. Turn ignition switch "ON".
2. Start engine and warm it up to normal operating temperature.
If engine cannot be started, go to "Diagnostic Procedure".
3. Select "DATA MONITOR" mode with CONSULT.
4. Check the voltage of MAS AIR/FL SE with "DATA MONITOR".
5. Increases engine speed to about 4,000 rpm.
6. Monitor the linear voltage rise in response to engine speed increases.
If NG, go to "Diagnostic Procedure". If OK, go to following step.
7. Maintain the following conditions for at least 10 consecutive seconds.
8. If 1st trip DTC is detected, go to "Diagnostic Procedure".
OVERALL FUNCTION CHECK
PROCEDURE FOR MALFUNCTION D
Use this procedure to check the overall function of the mass air flow sensor circuit. During this check, a 1st trip DTC might not be confirmed.
With Generic Scan Tool
1. Start engine and warm it up to normal operating temperature.
2. Select "MODE 1" with GST.
3. Check the mass air flow sensor signal with "MODE 1".
4. Check for linear mass air flow sensor signal value rise in response to increases to about 4,000 rpm in engine speed.
5. If NG, go to "Diagnostic Procedure".
Without Scan Tools
1. Start engine and warm it up to normal operating temperature.
2. Check the voltage between ECM terminal 54 (Mass air flow sensor signal) and ground.
3. Check for linear voltage rise in response to increases to about 4,000 rpm in engine speed.
4. If NG, go to "Diagnostic Procedure".
WIRING DIAGRAM
DIAGNOSTIC PROCEDURE
COMPONENT INSPECTION
1. Reconnect harness connectors disconnected.
2. Start engine and warm it up to normal operating temperature.
3. Check voltage between ECM terminal 54 (Mass air flow sensor signal) and ground.
4. If the voltage is out of specification disconnect mass air flow sensor harness connector and connect it again.
Then repeat above check.
5. If NG, remove mass air flow sensor from air duct. Check hot wire for damage or dust.