P0505

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Idle Speed Control (ISC) motor opens and closes the throttle valve according to signals from the Powertrain Control Module (PCM). When a condition arises which demands a higher idle speed, the PCM will send a signal to the ISC motor which will extend the plunger of the ISC motor, thus opening the throttle plates and increasing the idle speed. When the higher idle speed is no longer needed, the PCM will reverse the polarity to the ISC motor which will cause the throttle plates to close and decrease the idle speed.

Conditions for Running the DTC

^ Closed Throttle Position (CTP) switch ON.

^ Battery voltage greater than 12 volts.

^ Engine coolant temperature is greater than 30°C (84°F).

Conditions for Setting the DTC

Throttle valve feed back check:

^ ISC motor movement less than 0.244°.

^ Above diagnostic will run 10 times continuous per drive cycle.

ISC motor voltage check:

^ No operation signal from the PCM.

^ Above diagnostic will run 2 times continuous per drive cycle.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will illuminate.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

^ The PCM will enter the Fail-Safe Function and stop ISC control.

Conditions for Clearing the MIL/DTC

^ The MIL will turn OFF after three consecutively passing cycles without a fault present.

^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.

^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for any of the following conditions:

^ If a DTC P0510 is set, diagnose the DTC P0510 first.

^ A stuck or binding throttle plate may cause a DTC P0505 to set. Check the throttle plate for smooth and even movement.

^ A short to ground in the CTP switch Circuit may cause a DTC P0505 to set.

^ Check the adjustment of the accelerator cable. Refer to Fuel Delivery and Air Induction / Throttle Cable/Linkage / Adjustments. Adjustments

^ A poor connection at the PCM. Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.

^ A damaged wiring harness. Inspect the wiring harness for damage and repair as necessary.

^ Inspect the engine for a large vacuum leak. Check for a condition that could cause a large vacuum leak, such as a incorrectly installed or faulty crankcase ventilation valve or a brake booster hose disconnected.

If a DTC P0505 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Electrical Diagrams.

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determine if a fault is present. The ISC motor RPM output control is disabled by the PCM until the engine has reached a normal operating temperature of at least 80°C (176°F). Output controls can be found on the Tech 2 scan tool under Special Functions.

3. If the ISC motor plunger did not extend with either switch turned ON, in Step 2 and no DTC is set, perform the Electrical Load Idle Up Signal table. Table C-1A Electrical Load Idle-Up Signal Check

8. Check for an open or short in the ISC motor control circuits or for a faulty ISC motor.