DTC P030: Idle Speed Control (ISC) Rpm Out Of Range: Action

1. PCM turns on the "SERVICE ENGINE SOON" MIL.

NOTE: Numbers in list refer to circled numbers in diagnostic flow charts, see Fig 1 and Fig 2 . For circuit identification see Fig 3.

1. Checking for ISC motor codes that can cause other problems.
2. Checking if cruise control is engaged causing idle problems.
3. Checking for proper ISC motor operation.
4. Many engine fuel and emissions system faults may cause unstable idle. If the base engine idle is not steady, the ISC may not be able to control idle to within the range of commanded idle speed.
5. Checking the PCM's ability to control the ISC motor by checking for signal present at ISC motor.
6. Checking for an open or short to ground in CKT 425 or CKT 426.
7. Checking the PCM's ability to control the ISC motor by checking for signal present at ISC motor.
8. Checking if ISC motor is receiving the signal and is not responding to it correctly. Voltage should fluctuate continuously between a negative and positive value.

Fig 1: DTC P030: Idle Speed Control (ISC) RPM Out Of Range Flow Chart (1 Of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC P030: Idle Speed Control (ISC) RPM Out Of Range Flow Chart (2 Of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 3: DTC P030: Idle Speed Control (ISC) RPM Out Of Range Flow Chart Circuit

Courtesy of GENERAL MOTORS CORP.