Check Engine light with an Err 3 on the radio.

Radio Displays CAL or CAL ERR

Step
Action
Yes
No
Schematic Reference: Radio/Audio System Schematics
1
Did you perform the Diagnostic System Check-Entertainment System?
YES Go to Step 2
NO Go to Diagnostic System Check - Entertainment System
2
Turn ON the ignition, with the engine OFF.
Turn ON the radio.
Does the radio operate normally?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Program the radio. Refer to Service Programming System (SPS) .
Turn OFF the ignition.
Turn ON the ignition, with the engine OFF.
Turn ON the radio.
Does the radio display CAL ERR?
Go to Step 4
Go to Step 5
4
Important: Reprogram the radio. Refer to Service Programming System (SPS) in Programming.
Replace the radio. Refer to Radio Replacement .
Did you complete the replacement?
Go to Step 5
--
5
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2

Question edited for clarity.
Question moved to model category.

It appears to be a software error that only the dealership or an auto electrician can fix!

https://www.google.com/search?q=2002+trailblazer+radio+cal+error

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Apr 22, 2013 - 20 posts - ‎4 authors

CHECK BATTERY ALTENATER

If the lights are flickering I would be checking for a loose or dirty battery connection. If the power to the cpu is intermittent ( indicated by flickering lights ) that is why the engine dies

Usually caused by a failing dimmer wheel/rheostat.

It could be a bad connection or a bad headlight switch, but there is also a safety switch on the car that turns the dash lights out when you lose your tail lights, so before you go any further check if your tail lights are working, your car may just be telling you about another problem.

i would go around the block connectors with a wire brush but make sure you disconnect the battery

loose connection.... i'd start with the alternator to make sure all the wires are secure... then the main connection to the fuse box in the engine compartment near the battery

Take both cables of the battery and clean them with a wire brush, reinstall them making sure those little 5/16 hex bolts are nice and tight in the battery. Trace the battery ground cable back to where it bolts to the engine block, make sure it is very clean and tight. There should be a body ground somewhere, this is a conductor between the engine block and the metal body part of the engine compartment- clean and tight as well. If you can't find the body ground, make one.
Now get on your hands and knees and inspect behind both front kick panels and under the dashboard valence, inside the car. You are looking for single or clusters of brown or black wires that are bolted to the body inside the car. Clean and tight for these as well. I promise, this is where your problem lies, but I'm betting on loose battery terminals right now.