P0505
Idle Air Control (IAC) Motor Circuit:
Connectors: A-21X, B-34, C-51 <M/T>, C-52 <A/T>:
CIRCUIT OPERATION
- The idle air control motor power is supplied from the MFI relay (terminal 1).
- The ECM (terminals 14,15, 28, 29)
TECHNICAL DESCRIPTION
- The amount of air taken in during idling is regulated by the opening and closing of the servo valve located in the air passage that bypasses the throttle body.
- If there is a malfunction of the IAC system, the actual engine speed will not be identical to the target engine speed.
- The ECM
DTC SET CONDITIONS
Check Conditions
- Vehicle speed has reached 1.5 km/h (0.93 mph) or more at least once.
- Under the closed loop idle speed control.
Judgment Criteria
- Actual idle speed has continued to be higher than the target idle speed by 300 r/min or more for 12 seconds.
Check Conditions
- Vehicle speed has reached 1.5 km/h (0.93 mph) or more at least once.
- Under the closed loop idle speed control.
- The maximum atmospheric temperature is lower than 45°C (113°F) during closed loop idle speed control.
- The engine coolant temperature is more than approximately. 82°C (180°F).
- Battery positive voltage is higher than 10 volts.
- Barometric pressure is higher than 76 kPa (11 psi).
- Intake air temperature is higher than -10°C (14°F).
Judgment Criteria
- The actual idle speed is more than 200 r/min higher than the target idle speed for 12 seconds.
Check Conditions
- Under the closed loop idle speed control.
- The engine coolant temperature is more than approximately 82°C (180°F).
- Battery positive voltage is higher than 10 volts.
- Power steering pressure switch: "OFF."
- Volumetric efficiency is lower than 40 percent.
- Barometric pressure is higher than 76 kPa (11 psi).
- Intake air temperature is higher than -10°C (14°F).
Judgment Criteria
- The actual idle speed is more than 100 r/min lower than the target idle speed for 12 seconds.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Idle air control motor failed.
- Open or shorted idle air control motor circuit, or loose connector.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools:
MB991502: Scan Tool (MUT-II)
MB991709: Test Harness Set
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 1. Check the idle air control motor using scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 22, Crankshaft Position Sensor.
4. Check the idle speed.
Standard value: 700 ± 100 r/min
5. Check the air conditioning idle up speed.
Standard value: 900 ± 100 r/min
If within specifications, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope With Intermittent Malfunction.
If not within specifications, go to Step 2.
STEP 2. Check the power supply line at idle air control motor connector B-34.
1. Disconnect connector B-34, and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 2 and ground.
- Voltage should be battery positive voltage.
4. Measure the voltage between terminal 5 and ground.
- Voltage should be battery positive voltage.
5. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 3.
If not within specifications, repair the harness wire between MFI relay connector A-21 X and idle air control motor connector B-34. Then go to Step 9.
STEP 3. Check the idle air control motor coil resistor.
1. Disconnect idle air control motor connector B-34.
2. Measure resistance between idle air control motor connector terminal 2 and either terminal 1 or terminal 3.
Standard value: 28 and 33 ohms at 20°C (68°F)
3. Measure resistance between the idle air control motor connector terminal 5 and either terminal 6 or terminal 4.
Standard value: 28 and 33 ohms at 20°C (68°F)
If within specifications, go to Step 4.
If not within specifications, replace the idle air control motor assembly. Then go to Step 9.
STEP 4. Check the idle air control motor operation using special tool MB991709.
1. Remove the idle air control motor.
2. Connect special tool MB991709 to the idle air control motor. (All terminals should be connected.)
3. Use the jumper wires to connect terminal 2 of the idle air control motor connector to the positive battery terminal.
4. Check to ensure that the motor operates when the terminals 1 and 3 of the idle air control motor connector are connected to the negative battery terminal using a jumper wire.
5. Use jumper wires to connect positive terminal 5 of the idle air control motor connector to the positive battery terminal.
6. Check to ensure that the motor operates when the terminals 4 and 6 of the idle air control motor connector are connected to the negative battery terminal using a jumper wire.
7. Install the idle air control motor.
If vibration is detected at each application of voltage to terminal combinations, the stepper motor is operating properly. Then go to Step 5.
If vibration is not detected at each application of voltage to terminal combinations, replace the idle air control motor. Then go to Step 9.
STEP 5. Check harness connector B-34 at the idle air control motor for damage.
If harness connector B-34 is in good condition, go to Step 6.
If harness connector B-34 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then go to Step 9.
STEP 6. Check the circuits at ECM connector C-51
1. Disconnect connector C-51
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 14, 15, 28, 29 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to "LOCK" (OFF) position.
If within specifications, go to Step 7.
If not within specifications, repair the harness wire between idle air control motor connector B-34 and the ECM connector C-51
STEP 7. Check harness connector C-51 at the ECM
If harness connector C-51
If harness connector C-51
STEP 8. Using the oscilloscope, check the idle air control motor.
NOTE: keep in mind that the waveform can only be observed when the idle air control motor is in operation.
1. Disconnect idle air control motor connector B-34, and connect test harness special tool (MB991709) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to the idle air control motor-side connector terminal 1, terminal 3, terminal 4, terminal 6 respectively.
NOTE: When measuring at the ECM or PCM side connector connect an oscilloscope probe to terminal 14, terminal 15, terminal 28 and terminal 29 in that order
3. Start the engine.
4. Turn the air conditioning switch to "ON" position.
5. Check the waveform when the idling speed increases by the idle air control. The waveform display lasts less than one second.
- The waveform should show a normal pattern similar to the illustration.
6. Turn the ignition switch to "LOCK" (OFF) position. If the waveform shows a normal pattern, it can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope With Intermittent Malfunction.
If the waveform does not show a normal pattern, replace the ECM or PCM. Then go to Step 9.
STEP 9. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0505 does not reset.