soobie_newbie67 Posted July 14, 2014 Share Posted July 14, 2014 (edited) OK. So here's whats happening. I've noticed a couple of times that my temp gauge would start to climb. After it got to the 3/4 up there area, i could turn on the A/C and it would cool down. I took notice that when the gauge started to climb, the fans didnt turn, so i was under the impression that my gauge just wasnt reading right. Well, I'm thinking it might be. Last night it started to climb, and watched it climb all the way to the "H" thinking nothing of it cause i thought it was my gauge. Well, i decided to plug my scan tool in and found out that at that point, with the gauge sitting on "H", that the ECU was only reading a temp of 178! I kinda thought, "That cant be right." and looked under the hood to investigate. Fans werent on, radiator damn near burnt me just to touch, and i looked in my resevior and it was filling up with coolant. I quickly turned my A/C on to get the fans on and my temp started to drop, but so did the ECU reading. It dropped to 167 on my scan tool. Took about a minute and half to go back to the normal spot on the gauge. So, to end with a question: Does the ECU and the Gauge use different sending units to tell engine temp? I really dont wanna overheat my car. I like my headgaskets. Oh, and here's a little more on what i saw with the coolant resevior: I looked under the hood and could see it rising, and when I hit the A/C and got the fans going, it stopped when i hit normal operating temp. When i got up this morning i looked under the hood and the resevior was back down to its normal level. Edited July 14, 2014 by soobie_newbie67 Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 14, 2014 Share Posted July 14, 2014 (edited) first, yes the Gauge has it's on sensor, separate from the ECU. They MAY share the same housing in a 2000, in the 90s, they were 2 separate sensors near each other. If you have one sensor with 3 wires, it performs both functions. You also need to discover why your fans aren't working right. They should probably be running on low, or one should be on, then the other strtas when the a/c is selected. It can be a little confusing as to the logic used to decide when to turn the fans on high vs low but - You may have a bad relay or other electrical issue. Any work done on the car recently? Something related to electronics or the cooling system? Could the thermostat have been replaced with a non-OEM unit? Edited July 14, 2014 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 14, 2014 Author Share Posted July 14, 2014 The shitty part is when i try to sit and monitor my car for the overheating, the fans will do their job and cycle. Every time this has happened to me it's been while I'm driving and in traffic. The exception with last night was that i was on some gravel roads following thunderstorms so I just stopped and checked everything out. It always randomly when I'm driving. Favorite times for the temp to randomly start climbing are at retardedly long stop lights and in heavy traffic. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 14, 2014 Share Posted July 14, 2014 seems more like HGs but, if you saw mal-functioning fans, that needs to be investigated I'd guess. If they sre intermittent due to -what? - a failing relay or bad ground conections. w'ever - you will def. get overheating when stopped. has the car blown coolant OUT of the overflow tank? Does the car have a working OEM-style thermostat? Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 14, 2014 Author Share Posted July 14, 2014 Did not blow out, level in the reservoir just came up a little higher than usual. Bought a brand new thermostat from the dealer cause this is a fresh rebuild. I've put about 4k miles on it since the rebuild. Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 14, 2014 Author Share Posted July 14, 2014 (edited) After a good drive just got home and confirmed ECU is not telling the fans to come on. I pulled up to my house while the Guage was reading normal, turned off the A/C and tried waiting for the fans to come on. Sure enough the temp started climbing and the fans didn't turn on. At normal operating temp (by the gauge) my scan tool says 168 degrees. Definitely looking at the coolant temp sending unit, but which one? If there's 2, which one is the gauge and which one is the ECU? Edited July 14, 2014 by soobie_newbie67 Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 14, 2014 Share Posted July 14, 2014 (edited) IIRC, single sensor will have 3 wires. Engine Temp sensor will have 2 on the 2 sensor cars. Gauuge has a single wire. Located on the xover pipe I think. here's a 2 sensor drawing; probably find some other pics, maybe a youtube video on-line. Edited July 14, 2014 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
Caboobaroo Posted July 14, 2014 Share Posted July 14, 2014 It should be a single sending unit, located in the same spot as the older cars, like it's shown above. Try replacing it and see if that helps. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 14, 2014 Share Posted July 14, 2014 yeah, like he said might look like this; Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 16, 2014 Author Share Posted July 16, 2014 Anyone have a wiring diagram? I bought and installed a new sensor and now the ECU is reading coolant temp and turning the fans on, but the gauge is no longer working, and with the help of a friend found out that wiggling the plug makes the gauge bounce up and then fall back to cold. So, by the looks of it, which ever of the 3 wires is for the gauge is not getting a good connection. I know its not the ground wire in the circuit cause even though the gauge isnt working, my scan tool shows my engine temp. No codes. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 16, 2014 Share Posted July 16, 2014 did you install the new sensor with some kind of thread treatment? It might rely on the threads for a ground connection (not sure) try everything else first but, new sensor could be bad I suppose. Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 16, 2014 Author Share Posted July 16, 2014 I didn't put anything on the threads cause the new sensor had an o - ring on it. I just need to know which of the 3 wires is for the gauge. Wonder if my Chilton manual has the diagram.... Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 16, 2014 Share Posted July 16, 2014 The one with 12v on it with the key on. Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 17, 2014 Author Share Posted July 17, 2014 (edited) well, interesting new problem. Did a power test and got 10.3v, 4.8v, and 0v (that was the black "assuming" ground) My interesting new problem is this: I returned the first new sending cause after taking my DMM and doing a test, on the both the 10v and 5v circuits i couldnt get them to cut out no matter how hard i shook or pulled on the connector. So i'm assuming my new sending unit was bad out of the box. But now with the new one, when my engine is completely cooled down to ambiant temp, the gauge goes straight for the center where the fully warmed up normal op temp is, and as the car warms up to operating temp (while watching on my scan tool) the gauge climbs all the way to "H". Did i get another bad sending unit? Edited July 17, 2014 by soobie_newbie67 Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 17, 2014 Share Posted July 17, 2014 (edited) You may need to refresh some ground connection somewhere. They can get corroded. If you put your original sensor in, what readings do you get? battery and charge circuit OK? Edited July 17, 2014 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
soobie_newbie67 Posted July 17, 2014 Author Share Posted July 17, 2014 (edited) Alright. So when i make a discovery i have a bad tendency not share how i fixed it. NOT THIS TIME! I bought a ECT sensor from the dealer which was only 3 dollars more than the O'Highlies crappy Import Defect sensor, which 2 were bad out of the box. The dealer sensor fixed all the issues i was seeing and then some. My IAC used to be F**King up as well with 3k rpm cold starts, RPM oscillations, super low idling (300 rpms!) and stalling at take off. All thats gone. I read my Chilton manual and it says this bugger (ECT sensor) helps control ignition timing and injector pulse width. Go figure. My car actually runs better now that i have a good OEM sensor. Gauge now works correctly in correspondence with the temp readings on my scan tool, fans come on at 203 degrees on the spot. Damn i'm happy now Wanted to add: This sensor was bad but DID NOT throw a code. The only way i was able to tell it was bad was with my scan tool and watching the temp reading on live data. Please Read my original post to see what temp readings i was getting! Edited July 17, 2014 by soobie_newbie67 Quote Link to comment Share on other sites More sharing options...
Olnick Posted July 17, 2014 Share Posted July 17, 2014 Congratulations! Great feeling. I know I had to replace an ECTS many years ago--and suddenly it felt like I was driving a brand new car! Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 18, 2014 Share Posted July 18, 2014 yeah that sensor, and knock sensors, are kinda famous for causing marginal-running consditions with no code thrown. sounds like you're in love with the car again! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.