E030

Code E30:

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 E30 sets because the actual engine speed never reaches desired rpm signifying a slow or failed ISC motor. The ISC motor connector is located behind the alternator.

TEST CONDITIONS:

1. Codes E21, E22, E24, E26, and E27 not set.
2. Vehicle speed = 0.
3. Throttle switch closed.
4. Battery voltage greater than or equal to 11.0 volts.
5. The difference between actual engine speed and commanded engine speed is 152 RPM or greater.
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, power steering 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 P.0.1, 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".