P0506
DTC P0506: Idle Control System RPM Lower Than ExpectedIdle Air Control (IAC) Motor Circuit Part 1:
Idle Air Control (IAC) Motor Circuit Part 2:
CIRCUIT OPERATION
- The idle air control motor power is supplied from the MFI relay (terminal 4).
- 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
DESCRIPTIONS OF MONITOR METHODS
Difference between actual and target idle speed is over the specified value.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Misfire monitor
- Exhaust gas recirculation (EGR) system monitor
- Fuel system monitor
Sensor (The sensor below is determined to be normal)
- Volume airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Conditions
- Under the closed loop idle speed control.
- The engine coolant temperature is more than approximately 77 °C (171 °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 (22.4 in.Hg).
- Intake air temperature is higher than -10 °C (14 °F).
- 60 seconds have elapsed from the start of the previous monitoring.
- Target idle air control motor position is more than 100 steps.
Judgment Criteria
- The actual idle speed is more than 100 r/min lower than the target idle speed for 12 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to, Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists
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 harness damage, or connector damage.
- ECM failed.
- PCM failed.
- Throttle valve area is dirty.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
- MB991709: Test Harness
STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958, read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P0506 set?
YES: Refer to Diagnostic Trouble Code Chart.
NO: Go to Step 2.
STEP 2. Check the throttle body (throttle valve area).
Q: Is the throttle valve area dirty?
YES: Perform cleaning. Refer to Throttle body (throttle valve area) cleaning. Then go to Step 14.
NO: Go to Step 3.
STEP 3. Check connector B-34 at idle air control motor for damage.
Q: Is the connector in good condition?
YES: Go to Step 4.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 4. Check the idle air control motor coil resistance.
1. Disconnect the idle air control motor connector B-34.
2. Measure the resistance between idle air control motor connector terminal No. 2 and either terminal No. 1 or terminal 3.
Standard value: 28 - 33 Ohms [at 20 °C (68 °F)]
3. Measure the resistance between idle air control motor connector terminal No. 5 and either terminal No. 4 or terminal No. 6.
Standard value: 28 - 33 Ohms [at 20 °C (68 °F)]
Q: Is the measured resistance between 28 and 33 Ohms?
YES: Go to Step 5.
NO: Replace the idle air control motor. Then go to Step 14.
STEP 5. Check the power supply voltage at idle air control motor harness side connector B-34.
1. Disconnect the connector B-34 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 2, No. 5 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 7.
NO: Go to Step 6.
STEP 6. Check connector A-18X at MFI relay for damage.
Q: Is the connector in good condition?
YES: Repair harness wire between MFI relay connector A-18X (terminal No. 4) and idle air control motor connector B-34 (terminal No. 2, No. 5) because of open circuit or short circuit to ground. Then go to Step 14.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 7. Check the power supply voltage at ECM connector C-51
1. Do not disconnect the connector C-51
2. Measure the voltage between terminal No. 14, No. 15, No. 28, No. 29 and ground by backprobing.
- The voltage is 1 volt or lower for approximately 3 seconds, then changes to the battery positive voltage when the Ignition switch is turned from the "LOCK" (OFF) position to the "ON" position.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 10.
NO: Go to Step 8.
STEP 8. Check connector C-51 at ECM
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 9. Check for open circuit and short circuit to ground between idle air control motor connector B-34 and ECM connector C-51
a. Idle air control motor connector B-34 terminal 1 and ECM connector C-51 (terminal No. 14)
b. Idle air control motor connector B-34 (terminal No. 3) and ECM connector C-51 (terminal No. 28)
c. Idle air control motor connector B-34 (terminal No. 4) and ECM connector C-51 (terminal No. 15)
d. Idle air control motor connector B-34 terminal 6 and ECM connector C-51 (terminal No. 29)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 10. Check connector C-51 at ECM
Q: Is the connector in good condition?
YES: Go to Step 11.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 11. 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 battery (+) terminal.
4. Check the ensure that the motor operates when the terminals No. 1 and No. 3 of the idle air control motor connector are respectively connected to the battery (-) terminal using a jumper wire.
- Vibration should be present at each application of voltage to test clip combination.
5. Then. Use jumper wires to connect the terminal No. 5 of the idle air control motor connector to the battery (+) terminal.
6. Check the ensure that the motor operates when the terminals No. 4 and No. 6 of the idle air control motor connector are respectively connected to the battery (-) terminal using a jumper wire.
- Vibration should be present at each application of voltage to test clip combination.
7. Install the idle air control motor. Refer to Throttle Body - Disassembly and Assembly.
Q: Is the idle air control motor operating properly?
YES: Go to Step 12.
NO: Replace the idle air control motor. Then go to Step 14.
STEP 12. Check for harness damage between MFI relay connector A-18X (terminal No. 4) and idle air control motor connector B-34 (terminal No. 2, No. 5).
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair it. Then go to Step 14.
STEP 13. Check for harness damage between idle air control motor connector B-34 and ECM connector C-51
a. Idle air control motor connector B-34 (terminal No. 1) and ECM connector C-51 (terminal No. 14)
b. Idle air control motor connector B-34 (terminal No. 3) and ECM connector C-51 (terminal No. 28)
c. Idle air control motor connector B-34 (terminal No. 4) and ECM connector C-51 (terminal No. 15)
d. Idle air control motor connector B-34 (terminal No. 6) and ECM connector C-51 (terminal No. 29)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 14. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0506 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.