DTC 30

Fig. 21 Idle speed control throttle switch wiring circuit:

Code 30 indicates that either of two conditions have occurred. The first possible condition is that, after commanding the ISC motor to retract for 15 seconds, the actual RPM remained more than 150 over specified RPM and throttle angle remained greater than 2.5°. The second possible condition on is that, after commanding the ISC motor to extend for 15 seconds, the actual RPM remained more than 150 below specified RPM and throttle angle remained less than 9°. Possible causes of this condition are:
a. TPS improperly adjusted.
b. ISC motor improperly adjusted.
c. Defective ISC motor.
d. Defective throttle switch.
e. Defective wiring or electrical connectors.
f. ECM not able to process signals properly.
1. Perform switch tests and, if code .7.2 is set, refer to code .7.2. If code .7.2 is not set, enter diagnostics and select output cycling code .9.6.
2. If ICS motor extends and retracts, check for binding or misadjusted TPS. If TPS is satisfactory, check ICS motor for proper adjustment.
3. Turn ignition off for 10 seconds, then on for 5 seconds. Start engine and run for 20 seconds, then enter diagnostics.
4. If code 30 is still stored as a hard code, substitute new ECM and retest for code 30.
5. If ICS motor does not extend and retract when code .9.6 is selected, check for binding throttle linkage. If linkage is not binding, disconnect ICS connector and connect jumper wire between harness pins A and B, and a test lamp between pin D and ground.
6. If test lamp does not light, turn ignition off, reconnect ISC motor and disconnect orange (P3) connector. Measure resistance between terminals 2 and 5. If infinite resistance is recorded, repair open in circuit. If resistance reading indicates a short circuit, repair short and ensure ECM is not damaged. If resistance is between 4 and 100 ohms, check circuits 425 and 426 for a short to ground. If circuits are satisfactory, check for faulty ECM or ECM connector and repair or replace as necessary.
7. If test lamp flashes in three second intervals, reconnect test lamp between pin C and ground. If test lamp does not light, refer to step 6. If test lamp flashes in three second intervals, proceed to step 8.
8. Connect test lamp between pins C and D. If lamp flashes every three seconds or does not light at all, check for faulty ECM or ECM connector and repair or replace as necessary. If test lamp flashes continuously, check for loose ISC terminals or a faulty ISC motor and repair or replace as necessary.