Intermittent Coolant Sensor Issue - Pontiac Solstice Forum
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post #1 of 46 (permalink) Old 10-09-2008, 08:38 AM Thread Starter
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Location: Pickering, Ontario
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Intermittent Coolant Sensor Issue

I did a search on the forums but I didn't see any similar issues. Just wondering if anyone had the same problems. I recently blew my water pump which was replaced and shortly after I experienced an intermittent problem with the coolant sensor. I noticed that the fan would run when the engine is cold and the A/C wasn't working. I checked the coolant temperature on the DIC and it indicated "---". After a day or so, it would go back to normal. The shop told me to replace the thermostat, sensor and connector. I replaced all 3 however it continues to happen. Over the weekend it worked until about Sunday night and then went out again. The CEL came on. It sat in the driveway for 2 days and on Wednesday took it back in to the shop. They tinkered around with a few things and then started working again and the CEL turned off. Later that night after dinner, the CEL came on again and the coolant sensor was not registering any temperatures. Please help!

VIN 103423, Sly/Ebony, AC, ABS, LSD, MP3, Monsoon, Power, Leather
Mods: RK Sport Body Kit, RK Sport Blister Ram Air Hood, Fujita CAI, Bi-Xenon HID 8000K Conversion, 19" Moda MD1 w/ Kumho Ecsta SPT, Stubby Antenna, Debadged, Autobot Emblems, Wind Screen
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post #2 of 46 (permalink) Old 11-25-2008, 11:57 AM
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My '06 car is doing this right now at 36,600m. The dealer wants like $300 bucks to "look at it and determine the problem". I told them I would rather crap a life-size replica of myself then spend $300 to replace a $15 part.

DELPHI Part # TS10076 Actual Original Equipment Part $15.49

2007 PONTIAC SOLSTICE GXP 2.0L 1998cc 122 cubic inch L4 FI Turbo (X) Auto Parts

Easy to fix too. Luckily my water pump didn't blow up like yours or else I would be genuinely pissed.

I have a feeling that many parts on this car are designed to expire after 36,000m...
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post #3 of 46 (permalink) Old 11-25-2008, 12:29 PM
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Sensor problem


I had this exact same problem. The fix was pulling the sensor plug off and cleaning the contacts and plugging back in. Problem solved. The sensor is on the back of the engine block on the passenger side behind the exhaust manifold. I think it is vulnerable to heat there and makes an intermittent connection. Try this and let me know if it works.

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post #4 of 46 (permalink) Old 10-08-2009, 11:55 AM
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Coolant Temp reads ---F, fan stays on

So add me to the list of folks with the exact same problem, at 21K miles. I leave my DIC on the Coolant temp display. Earlier this week, I noticed the temp was reading erroneously low on my normal drive home from work, around ~150 ish give or take 8 degrees. It normally should be around 190 - 210F depending on where I am. Then about 15 minutes later, the display went to "---F"

I tried unplugging/reseating the sensor connector, that didn't work. Tried cleaning the connector/sensor terminals, that didn't work either.

The dealer replaced the Engine Coolant Temp (ECT) sensor the following morning, and all was fine for 1 day - it went to ---F again last night, so this morning I turned on the engine and the radiator fan immediately kicked on as an expected result. Dealer just called and said that he pulled the codes again and saw that the thermostat was intermittently sticking open, so they're replacing that and also the connectors to be sure. looks like I may be at where CndnSol is. Sucks that I'm out of warranty too. Wonder if this is common enough that it'll turn into a TSB?

Vin #99 of 1st 1000.

Last edited by Double-0 99; 10-08-2009 at 12:04 PM.
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post #5 of 46 (permalink) Old 10-08-2009, 03:46 PM
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Originally Posted by Double-0 99
I'm out of warranty too. Wonder if this is common enough that it'll turn into a TSB?
Warranty coverage is not effected by a Technical Service Bulletin being issued. Out of warranty is out of warranty.

Any Service Manual, Technical Service Bulletin, Priliminary Service Bulletin, Part, Accessory, Sales or Product information found here on site, should be thought of as correct and accurate as of the date it was posted. After that any information or service procedure should be confirmed as still correct with your dealership.

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post #6 of 46 (permalink) Old 10-12-2009, 12:37 PM
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Definitely was the thermostat in my case

Well, I've had the car back for a couple of days now after getting the thermostat replaced (the o-ring was clearly blown causing it to not easily close or open as it should) and everything seems to be back to normal...Coolant temp readings normal (not too low or just displaying ---, and thus the fan is only coming on when the coolant is too hot).

I missed finding this related thread earlier in my searches too:
Failed Thermostat; Source of P0128 ECT Below Thermostat Regulating Temperature

And thanks for clarifying the TSBs, Small Dealer. I was always under the mistaken impression that all TSBs were free just like recalls, and the only difference was that TSBs were just not directly life threatening.
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post #7 of 46 (permalink) Old 02-23-2010, 10:59 PM
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I was hoping my car was unique and the thermostat problem was just a fluke, but I am having second thoughts. I have also kept my "DIC" selected for engine temperature. Last summer, the temp started registering too cool. I mentioned it to my dealer and he said not to worry about it. Of course about a month later the "DIC" went to "---F", the engine fan came on, and I lost the A/C. Yep, they replaced the thermostat.

Well guess what happened yesterday....ya, same thing....10 months later. Luckily, I have been covered by my warranty, but I am worried, this being the second time in such a short time period. I will have to check into the issue of the gasket blocking the movement of the thermostat. Makes the most sense to me so far.

Have had the car since Feb of 2006 and still love least my gas pedal doesn't stick and my brakes still work...


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post #8 of 46 (permalink) Old 08-18-2011, 03:58 PM
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This problem is still popping up among us Solstice drivers. Mine just did the same thing. A/C went out, Temp read ---F, and car started sputtering. I had a feeling it was my thermostat sticking open and temp sensor screwing up. And after reading this thread I am certain of it. Thanks for posting this guys.
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post #9 of 46 (permalink) Old 12-27-2011, 02:25 PM
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Master Airflow sensor

Out of the blue lastnight got the dreaded CEL and toogled thru and noticed that my coolant reading was ---. Hooked it up to the computer and got a code stating coolant reading. Looked at a few things and ended up cleaning the mass airflow sensor, cleared the codes and ran the the car for about an hour. So far so good. No CEL and the coolant reading is back.
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post #10 of 46 (permalink) Old 03-29-2012, 10:38 AM
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Back again... Mine is a 2007 (11/06 I purchased new). This problem occurred a few years ago for several months then ceased to be an issue all on its own. The combination being fans run from start, no A/C, dash reads ---, and CEL comes on. Randomly after a few minutes or sometimes a few days, everything back to normal. I now have an Android app called "Torque" which finally came into use as this issue resurfaced a couple of days ago. The code P0128 is displayed relating to ECT reading being "low". Somewhere else there must be another temperature sensor, as there is a monitor in the Torque app showing a normal temperature even though the dash display shows --- . The fact that as soon as the key is in the ignition position the cooling fans come on before starting is indicative all is probably ok, just the computer thinks it is hot. To me this rules out thermostate issues, keeping it at the ECT level. Maybe this time I will embark on the contact cleaning since it is random, not predictable or repeatable on demand. It does self correct, again at random. Since I live in a climate that A/C is almost always running (top up or down), the first clue while driving that the code is being trown, is the A/C stops running. Similarly, If I leave the dash display on temperature, as soon as the display changes to ro from --- I know the problem has come or gone.
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post #11 of 46 (permalink) Old 04-04-2012, 05:05 PM
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I have had the same problems off and on for over a year now. I have always caught it with the DIC display "---" and showed either pending or current P0128 code.
In each case SAE ECT always shows expected coolant temp with no hick up around the time the DIC rolls over to "---".
I have cleaned the connector a few times now and I clean the MAF after every oil change so I know it is neither of those.
I suspect that the thermostat is the problem in that during certain ECU system checks it fails to measure ECT within the expected range causing the pending P0128. If this happens enough times it will eventually set the DTC, but conditions have to be right. Also when it happens the ECU or BCU stops updating the DIC with the ECT as it's considered to be invalid. Fans turn on, idle goes up and a few other things to protect the engine.
When I get a chance this weekend or next I will replace my thermostat and see if the problem goes away once and for all..
I have 80,000 miles on my SKY and at least 40K of that are with no heat shield on the exhaust manifold and boosting.

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post #12 of 46 (permalink) Old 04-04-2012, 09:18 PM
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I'm having the same thing going on with my 06 solstice. I changed the thermostat not even 2 months ago. So I'm pretty sure it couldn't that again so soon. My DIC came on with the coolant reading ---F about 3 or four days ago. Still trying to figure it out.
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post #13 of 46 (permalink) Old 04-10-2012, 06:39 PM
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There is only one coolant temp sensor. The dash reads "---" because the ECM has faulted out the ECT sensor. Your torque app must be looking at the undefaulted signal. You may have a biased low sensor, stuck in range sensor, or the car is taking too long to heat up.


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post #14 of 46 (permalink) Old 04-14-2012, 07:27 AM
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P0128 --- no A/C fan always on
2006 NA bought used October 2011 43,000 miles.
Apparently means coolant did not come up to temperature quickly enough. OBDC looks at a number of sensors including coolant temp, intake air temp and more. I had this for a while. If the ambient temp was above about 75 degrees F it would not occur because the engine would warm up enough regardless of the fact that the thermostat was stuck open. I had purchased extended warranty with the car and it covered the $275 cost to replace the thermstat and seal. So far so good.

Dennis in MD
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post #15 of 46 (permalink) Old 06-22-2012, 06:51 AM
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Bad thermostat

Hi Guys,
I had the same thing as everyone else - changed the stat about 5 weeks ago and a couple of days back same crap again - local garage installed new temp sensor and it was OK for 2 days and went again. On line research tells me that if the engine temp does not reach normal range within approx 5 mins the code will kick in and give all the usual symptoms - this is why the problem can come an go - if the code is reset and you have a cool day things might reach operating temp in time although the stat is bad.
Anyway installed another one yesterday - the inner rubber seal was all twisted up in the stat spring - let's hope this is the last time as this is a pig of a job!
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