The word cal is displayed above the temperature display what is it?

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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For optimum calibration, drive to an open, level location away from large metallic objects or structures such as bridges, steel buildings, etc. Disable aftermarket electronic accessories and switch off all non essential electrical accessories (heated rear window, heater fan, A/C, map lamps and wipers) and make sure all doors are closed. Start the vehicle. NOTE: The vehicle remains in the CAL mode until the compass has been successfully calibrated. NOTE: While holding the Front Controls Interface Module (FCIM) 7 and 9 buttons down, the compass display first enters the ZONE setting mode (after 5 seconds) and then after another 5 seconds (approximately 10 seconds total), the compass display enters the CAL mode. Press and hold (for approximately 10 seconds) the FCIM 7 and 9 buttons until the CAL indicator appears in the display, then release the buttons. NOTE: If the CAL indicator does not turn off after the vehicle is driven in a circle at least 5 times, repeat the procedure. Drive the vehicle slowly at less than 5 km/h (3 mph) in a continuous circle until the CAL indicator disappears from the display and the compass heading is shown. If the CAL message does not turn off after driving in a circle at least 5 times (and the procedure has been repeated at least once), install a new compass module (integral to the interior rear view mirror). For additional information, refer to Interior Rear View Mirror.

Cranks won't start , Did you check for spark ,fuel pressure ?
Radio Setup .Will the vehicle communicate with a scan tool ? Fuel an temp gauges not working are probably bad step motors inside the instrument cluster that controls the gauges . Where do the gauges read 0 or something else ?
Engine Coolant Temperature Gage
The IPC displays the engine coolant temperature as determined by the PCM. The body control module (BCM) receives a class 2 message from the PCM indicating the engine coolant temperature. The BCM converts the engine coolant temperature into a percent gage deflection. The IPC receives a message from the BCM via the serial peripheral interface (SPI) indicating the requested gage position. The engine coolant temperature gage defaults to 38°C (100°F) or below if:
?€¢
The PCM detects a malfunction in the engine coolant temperature sensor circuit.

?€¢
The BCM detects a loss of class 2 communications with the PCM.

?€¢
The IPC detects a loss of SPI communications with the BCM.

Fuel Gage
The IPC displays the fuel level as determined by the PCM. The body control module (BCM) receives a class 2 message from the PCM indicating the fuel level percent. The BCM converts the fuel level percent into a percent gage deflection. The IPC receives a message from the BCM via the serial peripheral interface (SPI) indicating the requested gage position. The fuel gage defaults to E (empty) if:
?€¢
The PCM detects a malfunction in the fuel level sensor circuit.

?€¢
The BCM detects a loss of class 2 communications with the PCM.

?€¢
The IPC detects a loss of SPI communications with the BCM.

When the fuel level is less than a pre-determined value, the low fuel indicator illuminates.
DTC P0462
The fuel level sensor changes resistance based on fuel level. The PCM monitors the signal circuit of the fuel level sensor in order to determine fuel level. When the fuel tank is full, the sensor resistance is high and the PCM senses a high signal voltage. When the fuel tank is empty, the sensor resistance is low and the PCM senses a low signal voltage. The PCM uses the signal circuit of the fuel level sensor in order to calculate the total remaining fuel in the tank. The PCM sends the fuel level percent via the class 2 serial data circuit to the body control module (BCM). The BCM converts this data and sends a fuel gage percent deflection to the IPC via the serial peripheral interface (SPI) in order to control the fuel gage. The fuel level information is also used for misfire and EVAP diagnostics.

Have
For the DE 100 series radio, complete the following procedure, using a scan tool, in order to properly set up communication:

1. At the Main Menu screen, select: Diagnostics.
2. At the Vehicle Identification screen, select the following options:
?€¢
Model Year



?€¢
Passenger Car


3. At the System Selection Menu screen, select: Body.
4. At the Vehicle Identification screen, select the Platform type.
5. At the Body screen, select: Radio.
6. At the Radio screen, select: Special Functions.
7. At the Special Functions screen, select: Radio Setup.
8. At the Radio Setup screen, press ENTER. The following test will set up a new or existing radio.
9. Select one of the following options:
?€¢
USA/Canada



?€¢
Export


10. Press the ENTER key.
11. Verify that the scan tool displays "Test in Progress."
12. Verify that the scan tool displays "Test Completed Successfully."
13. Press EXIT on the scan tool.

Important: The radio set up will configure the following systems:
?€¢
LEARN VIN

?€¢
Diagnostic Trouble Codes

?€¢
Class 2 Radio Messages

?€¢
Country Code

?€¢
Chime Volume

?€¢
Chime Level

?€¢
12/24 Hour Clock

Without learning the VIN, the radio will display a locked message (LOC).
The radio setup procedure will also clear the following messages:
?€¢
CAL

?€¢
CAL ERR

?€¢
CALIBRATE

There are two fuses one in the right I/P junction block an one in the left I/P junction block ! The right is marked DK / RKE 10amp fuse. The left is marked A/C / CRUSE 10amp fuse ! I don't think these are the problem ! These fuses supply power to the microprocessor in the driver information center . According to my service information the microprocessor supply's power to the ambient air temperature sensor an to the compass.
This mode displays an 8 point compass heading on the left hand side of the DIC. The compass will display the current vehicle direction relative to one of 8 compass headings using N, NE, E, SE, S, SW, W, and NW for the readout. The ambient temperature displays on the right hand side of the DIC. If the ambient temperature is below 3?°C (37?°F), the temperature reading will toggle between displaying the outside temperature and the word ICE for two minutes. If the temperature is less than minus 40?°F for more than 2 seconds, OC will display. If the temperature is above 140?°F for more than 2 seconds, SC will be displayed. If OC or SC is displayed DTC's will be set. For compass calibration and compass magnetic variation adjustment refer to Electronic Compass Calibration .

hat is the code it just says cal code? sounds to be a calabration thing do you a built in gps?

This is for your compass.You will need to calibrate your compass.The directions are in your owners manual.

Ambient air temp sensor could be the cause. Normally located in front grille area.

The "OC" indicates your compass is "Out of Calibration". Below is the proceedure to recalibrate your compass.

Compass Calibration
The compass may need calibration if:

After five seconds, the display does not show a
compass heading (N for North, for example), there
may be a strong magnetic field interfering with the
compass. Such interference may be caused by a
magnetic antenna mount, magnetic note pad holder
or a similar magnetic item.

The compass does not display the correct heading
and the compass zone variance is set correctly.
In order to calibrate, the letters CAL must be displayed
in the mirror compass windows. If CAL is not
displayed, push in the COMP button for approximately
eight seconds or until the letters CAL are displayed.
The compass can be calibrated in one of two ways:

Drive the vehicle in circles at 5 mph (8 km/h) or less
until the display reads a direction, or

drive the vehicle on your everyday routine and after
several turns the compass will become calibrated and
will display a direction.

Good luck.

Have your resolved the issue stated above. I have been having the same problem. Now my display has stopped working completely.