E030

Diagnostic Chart.:

ISC Circuit:

DESCRIPTION:

The PCM/ECM controls engine idle by increasing or decreasing the throttle opening using the idle speed control motor (ISC). The ISC will be active in controlling idle speed at any time the throttle switch is closed. Code E030 sets because the actual rpm never reaches desired rpm signifying a slow or failed ISC motor. The ISC motor connector is located behind the alternator.

TEST CONDITIONS:

1. Codes E021, E022, E024, E026, and E027 clear.
2. Vehicle speed = 0.
3. Throttle switch closed.
4. Battery voltage greater than or equal to 11.0 volts.
5. Engine speed is greater than 152 RPM, different than desired.
6. Engine has been running for more than 7 seconds.
7. Engine not receiving a power steering load.
8. PCM/ECM is not commanding an idle speed anticipate.

FAILURE CONDITIONS:

1. TPS 14° or greater and ISC is retracting for 15 seconds.
2. TPS 2° and ISC is extending for 15 seconds.

ACTION TAKEN:

1. PCM/ECM illuminates "SERVICE ENGINE SOON" telltale light for entire key cycle.

NOTES ON FAULT TREE:

1. Checking for proper throttle switch, brake switch, park/neutral switch operation. The PCM/ECM must receive accurate switch status information in order to control idle.

2. Checking for proper ISC motor operation.

3. 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 152 RPM of commanded idle speed.

NOTE ON INTERMITTENTS:

Display PCM/ECM parameter ED01, manipulate TPS wiring and connectors, watch for TPS value to jump or skip. Observe throttle switch status (OFF) while manipulating affected wiring. If the status light flashes, check for intermittent open circuit on CKT 427. Verify that minimum air speed, ISC and TPS are set to specification. If idle is unstable, see DIAGNOSIS BY SYMPTOM-NO CODES for "Rough, Unstable, Incorrect Idle, Stalling".