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Discussion Starter #1
This happened to me last year. Coolant temp sensor went out, replaced it and all was well...

Now, its happened two more times. It's averaging about once every 10k miles. Thoughts on a possible root cause? Car is stock except for K&N CAI.
 

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I can't tell you why *your* engine likes to eat up these sensors. If your connecter and wiring (at the sensor) are in excellent condition, and the sensors (when they go bad) show a faulty meter reading (bad resistance for the existing temp) or a short to the housing, that to me, leaves maybe 2 things. One--as each one is installed, its over torqued a bit (starting some internal damage), or what ever brand you buy is not the best brand going for you. But at least if its going to be an ongoing (minor) problem, you could at least buy one from an auto parts dealer that sells theirs, with a lifetime warranty. That way other than time spent to R&R it, there is no cost to you.
 

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do u have a 160 t stat?
i had one and it hapened twice nd went back to stock one
 

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Discussion Starter #4
Stock thermostat. Could be some bad wiring, when the CAI was first installed it chewed through the harness that leads to the MAF before I noticed it and got it up out of the way.

That problem though manifested itself in bad readings from the MAF and a blown ignition fuse. After patching up the wiring, the MAF and ignition fuse have given no more problems.

Could this potentially be a grounding issue? Something else in that harness that is loose?
 

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^^^^ Both wires go from the sensor to the ECM. Damage to either wire between those 2 locations (intermittent or continuous), means that (that) *accurate* temp signal is a goner.
 

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Discussion Starter #6
Thoughts as to why the MAF wouldn't throw any errors first? Or, why direct replacement of the sensor masks the underlying problem for so long (it's been about 6 months since the last failure).

In any case, I'll tear apart my wiring fix and double check it. Thanks :)
 

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I would think that the MAF device sees and measures the air flow and temp going past it. If the ECT sensor goofs up, I would think that the ECM would start scheduling an incorrect air/fuel mixture (to lean or to rich) do to the loss of, or the incorrect value of, that signal source. But air flow would keep on being sucked into the engine, and the MAF would keep on reading that total flow and air temp. So if the MAF is fully functional, I see no reason for it to set a code of its own. But there could be a code set due to the loss of the ECT sensor reading.
I see that the 2 ECT wires are very close and join up with the MAF wire loom. Then work their way back to the ECM location. It might be a smart move to double check the wiring loom, in and near that ECT/MAF wire junction area.
 

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Discussion Starter #8
Thanks for all your help. I tore it back apart tonight, everything looked OK, but I was careful to get it back together and everything zip tied up out of the way. Took it for a short drive tonight, and everything seemed normal (which has always been the case after replacing the temp sensor anyway).

Going to pick up some conduit to make sure there is no contact between the wires and the top of the block (where the harness Y junction is between the MAF and the temp sensor). I'll update this thread in a few months if the problem truly was my faulty wiring before.
 

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Thanks for all your help. I tore it back apart tonight, everything looked OK, but I was careful to get it back together and everything zip tied up out of the way. Took it for a short drive tonight, and everything seemed normal (which has always been the case after replacing the temp sensor anyway).

Going to pick up some conduit to make sure there is no contact between the wires and the top of the block (where the harness Y junction is between the MAF and the temp sensor). I'll update this thread in a few months if the problem truly was my faulty wiring before.

Back from the dead. :smile2:

I have this exact situation.

--My wife's car is getting the red X and contact dealer.
--The AC shuts off and the temperature gauge drops to nothing.
--I already replaced the ECT sensor and thermostat

In addition, I had the exact same thing happen with my MAF wiring--it vibrated downward and made contact with the belt, chewing up the wires, blowing a fuse, CEL, etc.

What did you find out to fix this issue?
 

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Discussion Starter #10
I never found the root cause, and traded the car in before I ever had a permanent fix.
 

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I didn't know what indication would be displayed *if* an engine cooling temp gauge dropped off line (so to speak). But thinking that it dropped to zero temp, might be a command to shut the AC down for possible protection of all its components. If you did the maint on that MAF wiring problem, maybe you could T/S that ECT circuit a bit. Get say a 1/2 or 1 watt size 300 ohm resister (or as close to that value as you can get) from one of those DIY electronics stores. Use it to jump the 2 pins on the ECT connector and see if the gauge now reads in the range you normally see (an maybe also cancel the message). 300 ohms is approximately the resistance the ECT reads at 180 degrees. That value causes a change in the 5 volt signal from the ECM. That altered voltage then cause the temp gauge to display a certain value. Of course, either wire from the sensor to the ECM that is less than ideal, could cause an indication problem, an apparently a few other things. You are sure that the connector and sensor pins/sockets are in good condition an interlock securely with each other. An have visually checked as much of the wiring possible for any signs of a problem.
 

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Been busy... but here is an update.

I looked at where the MAF and ECT wiring meet--and didn't see anything really amiss. However, I did note that the wiring at the ECT connector was rather bent and "pinched."

While I hated to do so, I ordered a new AC Delco connector with wiring and ECT sensor.

Yesterday afternoon, I cut ~6" of wiring out and spliced in the new connector and installed the new sensor.

I went for a 40 mile test drive and it ran great--no red X, the temp gauge looked fine, and the AC worked!

Next morning (today) it did the exact same damn thing it always does in the morning when my wife goes to work--at about 8-10 miles, it threw the X and the temp gauge dropped to nothing.

Why would this only happen in the morning? When she is leaving work (in the afternoon), she will pull the negative battery cable to reset the code, reconnect, and then drive home just fine.
 
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