P0506-IDLE SPEED PERFORMANCE LOWER THAN EXPECTED

For a complete wiring diagram Refer to Section 8W.

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, MAF below 250 mg/tdc, air temp above -17.8° C (0° F), coolant temp is above 70° C (158° F), Evap purge below 100% duty cycle, 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.

Possible Causes

AIR INDUCTION SYSTEM LEAKS OR RESTRICTIONS

PCV SYSTEM LEAKS OR RESTRICTIONS

THROTTLE BODY

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.ACTIVE DTC

NOTE: It is possible for ETC DTCs to be set at the same time as this DTC. Proceed with this test only if the other DTCs that are present are ETC related, but clear them before proceeding. If any other DTCs are set, they must be diagnosed and repaired before continuing this test.

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.

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.AIR INDUCTION SYSTEM

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 3

3.PCV SYSTEM

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 4

4.THROTTLE BODY OPERATION

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 5

5.POWERTRAIN CONTROL MODULE (PCM)

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test. (Refer to 9 - ENGINE - STANDARD PROCEDURE)