Cadillac: 1988 seville service code, cadillac seville, throttle positioning sensor

Question
I have a 1988 cadillac seville. The engine light came on so I checked to see the service code and it came up as E030H. When I looked up this code, it says ",Idle Speed Control Circuit." What does this mean? What do I do? Do I have to replace any parts? If so, what ones. Thanks for the help.

Answer
The "H" on the end of the code tells you that it is a HISTORY code that had an intermittent fault at one time but self corrected itself.

The fault could be caused either by an intermittent fault in the ISC IIDLE SPEED CONTROL) motor, Which is the large electrically operated unit that is mounted on the throttle body that has a metal extension sticking out of it and is controlling your idle speed.

Also the fault can be an intermittent fault in the TPS (THROTTLE POSITIONING SENSOR) which is mounted on the oposite side of the throttle body and has 3 wires going to it and is small and colored black.

Tests on BOTH items needs to be performed to determine WHICH one is at fault.