E030

ECM Code E030:

DFI ISC Circuit:

DESCRIPTION:

The 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. At vehicle speeds less than 6 MPH, the ECM controls idle based on engine speed. When vehicle speed is greater than 6 MPH, the ECM controls idle based primarily on throttle opening (TPS) with adjustments to maintain a minimum engine speed. Code E030 is designed to detect engine speed out of limits high or low.

TEST CONDITIONS:

1. Codes E021, E022, E024, E026, and E027 clear.
2. 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. Not a cold start.

FAILURE CONDITIONS:

ISC plunger extending with TPS less than or equal to 9° or ISC retracting with TPS greater than or equal to 2.5° for 15 seconds.

ACTION TAKEN:

1. ECM illuminates "SERVICE ENGINE SOON" telltale light for entire key cycle.
2. ECM commands BCM to display "SERVICE SOON" message on CCDIC.

NOTES ON FAULT TREE:

1. Checking for TPS misadjusted.

2. Checking for proper throttle switch, power steering switch, park/neutral switch operation. The ECM must receive accurate switch status information in order to control idle.

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 150 RPM of commanded.

5. Out of adjustment minimum air rate, ISC or TPS can can cause ISC not to control idle or code E030 to set falsely.

6. Checking ISC motor circuits for proper operation.

NOTE: Throttle switch input to ECM must be jumpered in order to allow ISC to cycle.

NOTE ON INTERMITTENTS:

Display ECM parameter ED01, manipulate TPS wiring and connectors, watch for TPS value to jump or skip. Enter ECM inputs EI72 and observe throttle status - check for binding throttle linkage or throttle return spring weak. Verify that minimum air speed, ISC and TPS are set to specification. If idle is unstable, see DIAGNOSIS BY SYMPTOMS for "Rough, Unstable, Incorrect Idle, Stalling". A code E030 may be stored along with a code E019 shorted fuel pump circuit. If code E030 no longer appears after code E019 has been corrected, do not investigate any further. The voltage on the fuel pump feedback circuit made the ECM improperly test code E030.

Review the snapshot data parameters stored with this code to verily failure condition. If the failure conditioin is verified, check and repair intermittent wiring connection, or sensor.