QuestionQUESTION: Ok I've been bothering you about my 96 caddy deville with northstar problem and I'm stuck now and dont know what to do but put in shop. Its about the code p1660 cooling fan control circuits. I did the ground test you told me about(grounding the blue wire on relay 2...blue wire) changed all 3 relays and pcm. Im skeptical about changing the ect(engine coolant temp sensor) I heard that it controls the fans also. But it it was malfunctioning it would throw a different code right? im ol getting that p1660. I just want my fans to kick to high speed when their supposed to. And get rid of this check engine light. As for the ect sensor, I bought it bout a month ago but never changed it out cuzz someone told me on that car if something was wrong with it it would throw a code. I dont know what to do. I checked all the wires,good condition. I just hope its not this ect sensor. You told me one time to unplug the ect sensor but i never did cuzz its hard to get to. I just assumed theres nothing wrong with it cuzz no code. Any help would be greatly appreciated.
ANSWER: Your missing something very simple. when you replaced the 3 relays and the PCM did the P1660 code return as HISTORY or CURRENT ?.
If you unplug the ECT wsensor the cooling fans will automatically go to maximum speed. Try it. You will most likely get another code but don't worry about it, We can CLEAR it from the computer.
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QUESTION: It returned as current. And do I unplug the ect while car off right? What does it mean if i unplug it and fans automatically go on high or does nothing at all?
ANSWER: Try just turning ON the ignition key without starting the engine and unplug the ECT. See what the fans do.
Next start the car with the ECT still unpluggged and see what the fans do,
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QUESTION: last question b4 i do that. Would the a/c not working or the coolant level sensor have anything to do with it. I jumped the coolant level sensor to get rid of the "check coolant level" message and the fans did not come on at all so I took the jump off and plugged it back up. I know in order to change that sensor I would have to replace the whole expansion tank.
AnswerThe FIRST thing you need to undetrstand is that there are SWITCHES and there are SENSORS. You can jumper a SWITCH but you CANNOT jumper a sensor or you will permanently damage a diode within a major component such as the computers, the AC/Heater programmer and other various electronic modules.
The coolant level SENSOR is the ECT. You CANNOT jumper the wires or you will damage the computer.
The coolant level SWITCH is located on the bottom of the plastic radiator overflow jug. you CAN jumper this SWITCH to turn OFF the LOW COOLANT light without damaging anything.
If you JUMPER the AC LOW PRESSURE SENSOR you will damage the AC/Heater programmer and or the PCM computer.
If you jumper the AC LOW FREON SWITCH you will NOT damage anything.
If I had access to this vehicle I would have it diagnosed and fixed within 30 minutes.
Perform the test that I gave you previously.
