Location idle control sensor

Clean the throttle body, mass air flow sensor and idle air control motor. Replace the air filter.

Clogged EGR valve<utube src="ZiAuEKWMyNM" ></utube> when I had that problem this is what it was

A temp sensor out of range giving a false cold reading can cause high idle . A MAP sensor can also cause high idle by advancing the timing resulting in higher idle .

Before change computer #1 TPS sensor # 2 IAC sensor,that you should change first.

The daytime running lamps in your 2001 Chevrolet Impala are controlled by the Body Control Module (BCM) Here is a description of how the system works:

The ambient light sensor is a light-sensitive transistor that varies its voltage signal to the Body Control Module (BCM) in response to changes in the outside (ambient) light level. When the BCM receives this signal, the BCM turns ON either the DRL or the headlamp relay for auto headlamp operation. Any function or condition that turns ON the headlamps will cancel the DRL operation.
Thirty seconds after you start the ignition with the headlamp switch set in the OFF position, the DRL will perform one of two actions:

Illuminate the high beam headlights at a reduced intensity in daylight conditions
Illuminate the low beam headlights in low light conditions
The DRL/EXT lamps fuse in the top of the engine fuse block supplies battery positive voltage to both the DRL switch contacts and to the DRL relay coil. When the BCM energizes the DRL relay coil, current flows through the right high beam lamp, to the left hand high beam lamp, to the energized DRL relay switch contacts, to ground G101.
The high beam headlamps are now in series, and split the voltage so that the headlamps illuminate at halt intensity. The DRL operates when the ignition switch is in the RUN position, and the parking brake is not set or the transmission is not in park. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.

replace the temputer sensor it dont know to choke the motor or not so to speak

replace the idle air control valve {sensor}

things to check: check for engine vacume leak
carbon build up at throttle body. idle air contoller maybe stuck due to carbon build up or defective

all your sensors run off the 5 volt ref. so you will have to trace your wiring harness from the pcm\ecm all the way out under the hood to locate the broken or pinched wire.

have u checked the spark plugs?