GPEC

P0506-IDLE SPEED PERFORMANCE LOWER THAN EXPECTED

For a complete wiring diagram Consult Diagrams/Electrical.

Theory of Operation

The objective of the Idle Speed Rationality monitor is to evaluate the ability of the idle speed control system to achieve and maintain a steady idle, by monitoring engine RPM during idle. If engine RPM is not within a calibrated deadband of target idle speed, a timer is started. If the timer reaches a maximum threshold without any sign of the RPM trending towards control, a fault is generated.

- When Monitored:
With the engine idling in drive, the brake applied, engine run time below a calibrated minimum value, and no VSS, MAF/MAP, ECT, TPS, ETC, CKP Sensor, fuel system, or injector DTCs present.

- Set Condition:
Engine speed is 100 RPM or more below target idle speed for 30 seconds. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. ACTIVE DTC
NOTE: If any other IAC Motor or Throttle Body DTCs are present, they must be diagnosed and repaired before continuing this test.

Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

With a scan tool, select View DTCs.
Is the status Active for this DTC?

Yes

- Go to 2

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Checking For An Intermittent DTC

2. AIR INDUCTION SYSTEM
Inspect the air induction system for the following problems:
Restrictions - dirty air cleaner, foreign material trapped in the air intake tube, etc.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 3

3. PCV SYSTEM
Inspect the PCV system for the following problems:
Restrictions - sticking valve, collapsed hoses or tubes, obstructed passages or ports, etc.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 4

4. THROTTLE BODY OPERATION / IAC MOTOR OPERATION

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Inspect the throttle body for carbon build up or other restrictions.
Using a straight edge, verify that the throttle plate is not bent. If the throttle plate is bent, the throttle body must be replaced.
Start the engine.
While the vehicle is running, lightly tap on ETC Motor or IAC Motor where applicable, with your hand, and listen for the idle to raise.
Were any problems found or did the idle fluctuate while tapping on the ETC Motor or IAC Motor?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 5

5. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the throttle body and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM Verification Test.Powertrain Verification Test