Inspect for the following conditions:
. Restricted air intake system--Inspect for:
- Collapsed air intake duct
- Restricted air filter element
- Foreign objects blocking the air intake system
. Throttle body--Inspect for:
- Objects blocking the IAC passage or throttle bore
- Excessive deposits in the IAC passage and on the IAC pintle
- Excessive deposits in the throttle bore and on the throttle plate
. Large vacuum leak--Inspect for a condition that causes a large vacuum leak, such as a incorrectly installed or faulty PCV valve or brake booster hose disconnected.
When the intake air is restricted, the IAC tries to increase the idle. When it reaches its limit ( the pintle can't open any further), the PCM sets the high voltage code.
It could also be ice in the PCV. This can happen after a series of short trips when it's cold outside. The moister that forms in crank case vent system does'nt have a chance to evaporate, unless the engine reaches full operating temperature.