P0505

P0505

Component Location:

General Description
When the TP sensor's signal indicates closed throttle position and the engine is idling, the ECM adjusts the idle speed control actuator so that the engine runs at the correct idling speed, regardless of coolant temperature, load and etc. When the additional load applied in the engine, the air flow through the idle speed control actuator is increased momentarily to raise the idling speed.

DTC Description
The temperature of catalyst has an effect on emissions. Also, the PCM estimates the temperature of catalyst by intake air mass. By the way, the intake air mass is controlled by ISCA during idling. So, if the Integral of intake air mass is below the threshold value, the PCM judges that ISCA doesn't work properly.

DTC Detecting Condition:

Signal Waveform:

Monitor DTC Status

CAUTION: If any MAFS or ISCA codes are present, do ALL REPAIRS associated with them before proceeding with this troubleshooting tree.

1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode
2. Press F4(DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
4. Read "DTC Status" parameter
5. Is parameter displayed "History (Not Present) fault"?

CAUTION:
- History (Not Present) fault : DTC occurred but has been cleared.
- Present fault : DTC is occurring at present time.

YES
a. Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for loose or poor connections, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure

NO
a. Go to next step as below

System Inspection

Check for Restricted Intake or Exhaust System
1. Visually/physically inspect the following items:
- Air cleaner filter element for excessive dirt or for any foreign objects
- Throttle body inlet for damage or for any foreign objects
- Restricted exhaust system

2. Was a problem found in any of the above areas?

YES
a. Repair as necessary and go to "Verification of Vehicle Repair" procedure

NO
a. Go to "Air Leakage Inspection" procedure.

Air Leakage Inspection
1. Visually/physically inspect the air leakage in intake/exhaust system as following items,
If OK, go to next step
If NG, repair as necessary and go to "Verification of Vehicle Repair" procedure
- Vacuum hoses for splits, kinks and improper connections.
- Throttle body gasket
- Gasket between intake manifold and cylinder head
- Seals between intake manifold and fuel injectors
- Exhaust system between HO2S and Three way catalyst for air leakage

2. Check for air leakage in EVAP. Purge control valve
1. Remove the manifold side vacuum hose from the EVAP canister purge valve.
2. Using a hand vacuum pump apply specified vacuum (Approx. 15 in, Hg) to the manifold side of the valve
3. Does the valve hold vacuum?

YES
a. Go to "W/harness Inspection" procedure

NO
a. Repair as necessary and go to "Verification of Vehicle Repair" procedure

Terminal and Connector Inspection
1. Many malfunctions in the electrical system are caused by poor harness(es) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage
3. Has a problem been found?

YES
a. Repair as necessary and go to "Verification of Vehicle Repair" procedure

NO
a. Go to next step as below

Component Inspection

ISCA Inspection
1. Ignition "OFF".
2. Remove ISCA from Throttle body and Check for throttle bore, throttle plate and the ISCA passages for chocking and for any foreign objects. Repair or clean as necessary.
3. Ignition "ON" & Engine "OFF".
4. Connect scan tool and select "IDLE SPEED ACTUATOR" parameter on the "ACTUATION TEST" mode.
5. Activates ISCA by pressing "STAT" key.
6. Check the ISCA for clicking sound and visually verifying valve closes and opens.

CAUTION: Repeat numerous times to ensure valve reliability.

7. Is ISCA Valve moving freely and not carbon fouled?

YES
a. Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure

NO
a. Check ISCA valve for contamination, deterioration, or damage. Substitute with a known-good ISCA valve and check for proper operation. If the problem is corrected, replace ISCA valve and then go to "Verification of Vehicle Repair" procedure

Verification of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode
2. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter
4. Is parameter displayed "History (Not Present) fault"?

YES
a. System performing to specification at this time. Clear the DTC

NO
a. Go to the applicable troubleshooting procedure.