QuestionQUESTION: Can you help me fix this problem. I have a 96 caddy deville with northstar. My cooling fans are not working properly. I know theres two speeds and they come on when they're supposed to, just in low speed. When im in traffic my engine gets hot cuzz they wont kick to high speed. I got the code p1660 cooling fan control circuits. I changed all three relays and still no luck. I have schematics and everything I just need some help locating the problem or maybe you might know what it is. Any help would be greatly appreciated.
ANSWER: Try unplugging the ENGINE TEMP COOLANT SENSOR which has a black and a yellow wire attached to it which is located on the left side of the rear engine cylinder head and see if the fans run on HIGH. If they DO, Test the coolant sensor ohms per the temperature chart. If the sensor tests out OK, Ground the DARK BLUE wire at either relay # 2 or # 3. If the fans run on HIGH, Replace the PCM (computer).
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QUESTION: I know the coolant temp sensor is good cuzz it gives me a digital readout on the dash...or does that not mean anything. And you said GROUND the dark blue wire at relay 2 or 3? If that works,is it safe to leave like that or do I actually have to replace the pcm...those things are expensive for my car. Over 600 bucks.
AnswerOK, Try the GROUND test and if this causes the fans to run on high, You can purchase an aftermarket remanufactured computer from most any auto parts store for about $150.00.
NO, Do NOT leave the jumper in place as it will cause all sorts of driveability problems due to cooling down the engine temp to low and will also effect the AC system.
