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P0505

Idle Air Control (IAC) Motor Circuit:




Connectors:




CIRCUIT OPERATION
- The idle air control motor power is supplied from the MFI relay (terminal 1).
- The PCM (terminals 14, 15, 28, 29) drives the stepper motor by sequentially turning "ON" the power transistors in the PCM and providing ground to the idle air control motor (terminals 1, 3, 4, 6).

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 PCM checks the difference between the actual engine speed and the target engine speed.

DTC SET CONDITIONS

Check Area
- 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 Area
- 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 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 Area
- Under the closed loop idle speed control.
- Engine coolant temperature is more than approximately 82° C (180° F).
- Battery 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.
- PCM failed.

DIAGNOSIS
Required Special Tools:
MB991502: Scan Tool (MUT-II)
MD998463: Test Harness

STEP 1. Check the idle air control motor in one of the following two ways.
1. Using scan tool MB991502, go to Step 2.
2. Using an analyzer, go to Step 3.

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.




STEP 2. Check the idle air control motor using scan tool MB991502 or a tachometer.
1. Connect scan tool MB991502 to the data link connector or set up the tachometer.
2. Check the idle speed.
Standard value: 700 ± 100 r/min

3. Check the air conditioning idle up speed.
Standard value: 900 ± 100 r/min

If not within specifications, go to Step 4.

If within specifications, it can be assumed that this malfunction is intermittent. Refer to vehicle level Testing and Inspection.

STEP 3. Using the analyzer, 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 the idle air control motor connector A-40, and connect the test harness special tool (MD998463) in between.




2. Connect the analyzer special patterns pickup to the idle air control motor side connector terminal 1 (red clip on the special tool), terminal 3 (blue clip), terminal 4 (black clip), terminal 6 (yellow clip) respectively.

NOTE: When measuring at the PCM side connector, connect to terminal 14, terminal 15, terminal 28 and terminal 29 in that order.

3. Start the engine.
4. Turn the air conditioning switch "ON".




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. Stop the engine.
If the waveform shows an abnormal pattern, go to Step 4.

If the waveform shows a normal pattern, it can be assumed that this malfunction is intermittent. Refer to vehicle level Testing and Inspection.

STEP 4. Check the idle air control motor coil resistance using test harness special tool MD998463.
1. Disconnect the idle air control motor connector and connect the test harness special tool MD998463 to the idle air control motor.




2. Measure the resistance between the idle air control motor connector terminal 2 (the white clip on the special tool) and either terminal 1 (red clip) or terminal 3 (blue clip).

Standard value: 28 and 33 ohms at 20° C (68° F)

3. Measure the resistance between the idle air control motor connector terminal 5 (green clip on the special tool) and either terminal 6 (yellow clip) or terminal 4 (black clip).
Standard value: 28 and 33 ohms at 20° C (68° F)

If within specifications, go to Step 5.

If not within specifications, replace the idle air control motor.

Then go to Step 10.

STEP 5. Check the idle air control motor operation using special tool MD998463.
1. Remove the idle air control motor.
2. Connect special tool MD998463 to the idle air control motor.




3. Connect the positive terminal of the 6-volt DC power supply to the white and green clips of the special tool.




4. Check for idle air control motor vibration as you connect the negative terminal of the 6-volt DC power supply to each of these combinations of the special tool test clip in sequence.

a. Red and black
b. Blue and black
c. Blue and yellow
d. Red and yellow
e. Red and black
f. Red and black
g. Red and yellow
h. Blue and yellow
i. Blue and black
j. Red and black

- Vibration should be present at each application of voltage to test clip combination.

5. Install the idle air control motor.
If vibration is detected at each application of voltage to test clip combinations, the stepper motor is operating properly. Go to Step 6.
If vibration is not detected at each application of voltage to test clip combinations, replace the idle air control motor. Then go to Step 10.

STEP 6. Check the power supply line at the idle air control motor connector A-10.
1. Disconnect connector A-10 and measure at the harness side.
2. Turn the ignition switch "ON".




3. Connect terminal 2 with the ground via a 20-ohms resistor.
Measure the current at this time.

- The current should be 0.5 ampere or more.

4. Connect terminal 5 with the ground via a 20-ohms resistor.
Measure the current at this time.

- The current should be 0.5 ampere or more.

5. Turn the ignition switch "OFF".
If within specifications, go to Step 7.

If not within specifications, check the intermediate connector C-14, and repair or replace as required. Refer to vehicle level Testing and Inspection. If the intermediate connector C-14 is in good condition, repair the harness wire between the MFI relay connector C-59 and the idle air control motor connector A-40. Then go to Step 10.




STEP 7. Check the circuits at the PCM connector C-89.
1. Disconnect the connector C-89 and measure at the harness side.




2. Disconnect PCM connector C-90. Using a jumper wire, connect terminal 49 to ground and activate the MFI relay.
3. Turn the ignition switch "ON".
4. Connect the 14,15, 28 and 29 terminals with the ground via a 20-ohms resistor. Measure the current at this time.

- The current should be 0.3 ampere or more.

5. Turn the ignition switch "OFF".
If not within specifications, go to Step 8. If within specifications, go to Step 9.




STEP 8. Check the harness connector A-40 at the idle air control motor for damage.
If harness connector A-40 is damaged, repair or replace it.

Refer to vehicle level Testing and Inspection.

If harness connector A-40 is in good condition, repair the harness wire between the idle air control motor connector A-40 and the PCM connector C-89.

Then go to Step 10.




STEP 9. Check harness connector C-89 at the PCM for damage.
If harness connector C-89 is damaged, repair or replace it.

Refer to vehicle level Testing and Inspection.

If harness connector C-89 is in good condition, replace the PCM.

Then go to Step 10.

STEP 10. 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 a diagnostic trouble code is not being output.






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