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It is important to note that you will see wider fluctuations in engine temperatures with the AC off because the fans cycle on at 229 and off below 216 with the AC off.  This will be true if the AC is disabled due to low refrigerant. 

With the AC on and operational, the fans are on low full time.

The following details the cooling fan operation.  

The PCM will command fan operation when:


  • Low Speed Fan Operation
    • Engine coolant temperature exceeds approximately 106°C (229°F).
    • Transmission fluid temperature exceeds 150°C (302°F).
    • A/C operation is requested.
    • After the vehicle is shut OFF if the coolant temperature at key-off is more than 151°C (304°F) and system voltage was more than 12 volts. The fans will stay ON for approximately 3 minutes.


The fans will switch from low to OFF when the coolant drops below 102°C (216°F).


  • High Speed Fan Operation
    • Engine coolant temperature reaches 112°C(234°F).
    • Transmission temperature is more than 151°C (304°F).
    • When certain DTCs set.


The fans will switch from high to low (except DTCs set) when the coolant drops below 106°C (229°F).

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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