P030

This article has been updated with bulletin No.: 51-65-10.

DTC PO30: Part 1 Of 2:

Code PO30 - Part 2 Of 2:

PCM Circuit:

DESCRIPTION
The Powertrain Control Module (PCM) controls idle RPM by increasing or decreasing the throttle opening using the Idle Speed Control (ISC) motor. The ISC motor will control engine RPM any time the throttle position switch is closed. Code P030 sets because the actual RPM never reaches desired RPM signifying a slow or failed ISC motor.

TEST CONDITIONS
1. Codes P021, P022, P024, P026, and P027 not set.
2. Throttle position switch closed.
3. Vehicle speed less than or equal to 0 mph.
4. Battery voltage 11 volts or greater.
5. Actual idle engine speed is at least 152 RPM different from desired RPM.
6. Idle speed control start-up delay over.
7. Engine not receiving a power steering load.
8. PCM is not commanding an idle speed anticipate.

FAILURE CONDITIONS
1. ISC motor in the forward mode, throttle position 14 degrees or less and ISC is extending for 30.3 seconds.
OR
2. ISC motor in the reverse mode, throttle position 2.1 degrees or greater and ISC is retracting for 30.3 seconds.


ACTION TAKEN
1. PCM turns "ON" the "Service Engine Soon" Malfunction Indicator Lamp (MIL).

NOTES ON FAULT TREE
(Part 1 of 2)
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.

(Part 2 of 2)
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 from a negative to a positive value.