Quote:
Originally Posted by jcyuhn
Yeah, I would think with the single 4 connector temp sensor that your fans would come on. I don't know what's going on there...
It's difficult to imagine how ASR operation might be tied to coolant temperature - I can think of why to two would be related. Do you think it's more likely to be something like a poor or intermittent electical connection in the wiring harness? Perhaps one of the pins has partially backed out of a plug connection?
- JimY
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I would also think the fans would come on, regardless of engine temp, when the sensor is unplugged. But this morning, when cold, they did not. When the engine was warm/hot later on, they did. So that's an obvious sensor -- or sensor connector -- anomaly.
I understand that ASR is not directly related to coolant temp, but since idle speed control is related to coolant temp and ASR is related to idle speed, could there be something strange occurring in that triangle?
The wiring harness is relatively new, but I most definitely believe a poor/intermittent connection or signal is the culprit, especially since very high humidity on the first start of the day in the dead of summer will trigger the fault as readily as cold temps in the winter. That screams, "electrical." Something needs time (approx 10 minutes) to warm up and/or dry out, and I am leaning towards warm-up. And coolant does not need to reach operating temp. If I raise the temp to, say, 60, then go shopping for 20 minutes, when I get back the temp may be 50, but the car will start with no ASR fault.
Here is something else to chew on: In the summer, on this car and my previous one, I have observed that when driving down hill, or decelerating, coolant temperature drops. The hotter the engine temp, the more dramatic the drop. I can only conjecture that inertia is moving more coolant forward into the radiator, and/or slowing the escape of that which is already there. The temperature drop must also be occurring in the winter, but is less noticeable on the dash gauge.
On every occasion in winter driving when the ASR fault kicked when I was underway, it occurred only -- repeat only -- on deceleration (not necessarily with braking) and especially when going down hill, i.e., decelerating down an exit ramp; or decelerating down the curved, steeply inclined ramp of a parking garage; or, most notably, on a bitterly cold day on I-95 when decelerating from about 80 to 70 mph (no braking) in 20-degree weather.
My simple-minded theory is that, because of the faulty sensor, possibly related to internal corrosion, the computer is reading a rapidly fluctuating resistance (when the sensor or sensor connector is cold) and doesn't know what to do until the sensor/connector warms up and sends a more constant/stable signal. (During some recent online research, I happened across a experience someone had with a failing, corroded, coolant temp sender linked to their dashboard gauge. He/she described how the gauge would peg very hot, then drop to zero, repeatedly. I don't know how a an engine computer would react to something like that, but I suspect it would not be pleased.)
So, yes, I definitely believe it is a fault in a wire harness connector, or a sensor/component linked to said connector, and I have focused on the one that is 1.) most directly exposed to weather; 2.) which is directly involved in the coolant temperature behavior; and 3.) Which now appears to be exhibiting anomalous behavior (fans not running when disconnected if engine is cold).
Sorry for the small novel.
