Replaced One-wire Coolant Temperature Sensor with a Two-wire Sensor -My car had been stalling at stops, randomly changing rpm's while being driven, and hard idling badly. Several people suggested that I replace the engine coolant temperature sensor. I had recently added a new air filter, spark plugs, spark plug wires, PCV valve, fuel filter, and thermostat, and a few years ago the EGR valve had been swapped out for a different one. The original ECT sensor had only one wire coming from it, but I was assured by AutoZone that their two-wire sensor with included pigtail connector would work. Its directions stated I should connect either of its two wires to my car's existing signal wire, then attach the other wire to a ground. Here's where the problem begins. I've swapped its two wires between signal and ground just to be sure they weren't switched. I tried running it with only one of each of its wires. If the signal and ground are both connected, the car runs perfectly without hard idling or triggering the Service Engine Soon light and Low Coolant Light, however, the temperature gauge skyrockets within 5-10 seconds and stays red-lined even though the engine doesn't seem hot. If the ground is disconnected, leaving only the signal wire, both warning lights appear and the car idles violently for a few seconds before stalling out. Did I receive a faulty ECT sensor, am I not hooking it up correctly, or is it not even possible to replace a one-wire with a two-wire sensor? Please offer me any suggestions you may have.
By the way, I forgot to mention that I am unable to obtain a reading from the OBD connector under the dash. My car, as far as I can tell from the research I've done, was built during the transition period between OBD 1 and OBD 2. The connector is version 1, but the wires are located in different positions compared to a typical connector. I've been told the computer is version 2. Every parts store and mechanic who have looked at it can't tell me why the SES light is on, and my only option is to pay a dealership $80 for a simple reading. I'm not willing to pay that much for so little.
October, 1, 2011 AT 4:49 AM
I understand the money issue. As far as the temp gauge, it sounds like you have a bad sensor. I'm not sure why they have a two wire set up. Have you checked any other parts store? I would look for a direct fit part. I hate when they make one part and then modify it to fit many. It usually doesn't work correctly. See if you can find the correct sensor first. If you can't I would take the one back you have and get a new one.
October, 1, 2011 AT 6:56 PM
Based on the research I've done (phone calls and searches on local parts stores' websites), manufacturers of these ECT sensors no longer make single-wire versions. I'll have to keep trying different ones until I get a match.
October, 1, 2011 AT 7:39 PM
I will assume the dealer doesn't have one either. It seems they discontinue parts a lot faster than the did years ago. I think they expect everyone to buy a new car all the time.
October, 1, 2011 AT 8:18 PM
Also, be sure that there are no air pockets in the cooling system. You didn't specify whether you had the 3.1L or the 3.8L V6, but be sure to bleed all of the air out of the system. An air pocket could possibly cause erratic temperature readings. It may be necessary to safely raise the front of the vehicle when purging an air pocket - sometimes they can be stubborn to remove.
October, 4, 2011 AT 11:54 PM
My Regal has a 3.8L V6 in it, and since I replaced the thermostat, my upper radiator hose has been almost completely void of coolant when the engine is cold. After it warms up, that hose becomes stiff, but it doesn't feel like liquid. I heard this can be caused by a leaky gasket or crack allowing air to get in the system, but I never had a problem with this until replacing the ECT sensor. There is a bleed valve on the thermostat housing, but I am unable to make it purge the system of air. I'll keep doing more research on this subject.
October, 5, 2011 AT 1:51 AM
I've also noticed now that my fans no longer turn on by themselves, both when the car is hot and when the air conditioning is turned on. This may be why the engine is overheating. Could the fact that the ECT sensor may not be working be preventing my fans from starting when needed, which then registers as overheating on the temperature gauge?
October, 5, 2011 AT 2:15 AM
Yes, the temp sensor sends the signal to the computer of the coolant temp. From there, power is sent through a relay and then to the fans. NOTE: Make sure the fan motors haven't gone bad.
October, 5, 2011 AT 2:39 AM
LOOK FOR THIS
1995 BUICK REGAL 3.8L V6 : Electrical-Switch & Relay : Coolant Temperature Vacuum Control Switch