NEED HELP CEL and Engine Coolant Temp Gauge not Functioning

[$ Khalid ! 9130]

Hi everyone it's me again

Well today I had some work to do outside the city. So I went out. Started my TB, check engine light was on as always, so I didn't pay attention to it and set out. It was when I was on the highway, I noticed the Engine Coolant Temp Gauge was at 0!

I quickly pulled over to the side, stopped the car, checked the engine and everything was fine. The weather was quite cool today so I had not used my A/C, I switched it on and was blowing hot air only! I took a chance and thankfully made it back home with no issues.

Any idea what could be the problem. I still need to get the code read so I hopefully I will have more info soon. Anyone have similar symptoms, etc to weigh in here?

As always much appreciated

 

[Sparky]

1) gauge stepper could have taken a dump
2) sensor could have taken a dump
3) wiring to the sensor could be shot

Easy way to test would be if you have Torque and an OBDII adapter. See if it shows engine coolant temp or not. If it matches the gauge (0) then your sensor and/or wiring is messed up (likely the sensor, honestly). If it shows a normal reading then it is likely the stepper motor.

Use Torque to check the SES light code also.

If you don't have Torque but you have an Android device of some sort (phone, tablet, etc) I highly suggest getting it. $25-30 investment is well worth it!

 

[$ Khalid ! 9130]

I would think its the latter of the two, but I hope not. Because the gauge motor does the reset thing when I start the TB.

I guess it is time to get an OBDII scanner

On a side note would it be advisable to still drive the TB or is it better off at home ?

Thanks

 

[Sparky]

If the sensor is bad it won't ever reached closed loop as it won't know the engine temp, so you'll be burning more fuel and - if left that way too long - it can clog the cat. That, and if you do start to overheat you won't know until something blows up.

So... I'd prefer not driving it a lot without a working sensor, but if you have somewhere to go - especially shorter trips - it won't really hurt anything.

 

[$ Khalid ! 9130]

If the sensor is bad it won't ever reached closed loop as it won't know the engine temp, so you'll be burning more fuel and - if left that way too long - it can clog the cat. That, and if you do start to overheat you won't know until something blows up.

So... I'd prefer not driving it a lot without a working sensor, but if you have somewhere to go - especially shorter trips - it won't really hurt anything.

Thanks. I was really worried today as I was in the middle of the highway when I pulled over to check everything. My trips are usually short but today was a looonng drive almost 300 KM (186 Miles) and I am really glad nothing happened. I think this will need immediate attention.

 

[$ Khalid ! 9130]

One thing anyone know where exactly this sensor is? I would have preferred to see whether there's a problem with the sensor or no, but sadly the shop near my house only reads codes and doesn't display the readings. If only they would ship faster here.

 

[Sparky]

Next to the thermostat, driver side of the engine, behind/below the alternator.

While you're in there it might make sense to replace the thermostat too since it isn't an uncommon thing to go bad and it would be easier to do it all at once.

 

[xavierny25]

@Sparky didn't they change the location for the 05 and up models?

 

[Sparky]

Oh, right. It was actually 06 I think, when they changed the head design. It moved to the backside of the engine.

 

[$ Khalid ! 9130]

Will gave to start poking in there

 

[$ Khalid ! 9130]

Took the TB out for a small errand and boom the Gauge was working perfectly. CEL was still on, but the Engine Coolant Temperature was showing perfect readings.

 

[xavierny25]

Has happened to me once I just called it a glitch in the matrix.

 

[$ Khalid ! 9130]

Has happened to me once I just called it a glitch in the matrix.

Hopefully it's the same thing here

 

[Eric04]

With my 2004 I6, I originally noticed a wandering temp gauge about two weeks ago. Some days it read fine, others two ticks left of 210. My thermostat was around two years old(dealer replaced before I bought it)so naturally I blamed it.

After replacement my issue only got worse. Temp consistently drifted to cooler readings but no CEL, despite the scan tool occasionally showing temps in 170s range. Upon replacing the sensor I found the engine ran at a consistently cool temp of 185 and the needle agreed, sitting one and a half ticks left of 210. After about three days of that the CEL did illuminate.

I had a point with this.... Oh, yeah. If your CEL is on you should keep on it until you find out why. It *seems* the wandering needle is indicative of a bad sensor but keep chasing it down, man. Good luck.

 

[Chickenhawk]

Wandering needle is usually sensor. They live a hard life, immersed in coolant. Steady needle below center tick is usually thermostat. Be especially careful of wandering needles AND too low a temp. It doesn't matter if the PCM THINKS the engine is cold or the engine really IS cold; the result is a richer mixture than needed and a cooked cat in relatively short order. This is why we often advise changing both at the same time.

I chose NOT to follow my own advice. My needle wandered on the highway, but it hit 210 when not wandering. I surmised sensor, and I wanted to start with it, just to confirm for the benefit of members of this forum. I was correct. Temp has been rock solid, half a tick to the right, for the last four years.

 

[Sparky]

I just did both at the same time on mine, just to be sure.

 

[$ Khalid ! 9130]

Well I have been getting a constant reading past two days. And just yesterday the CEL light disappeared as well . This cars playin me !!!

 

[$ Khalid ! 9130]

Oh well. Same thing happened to me today. No reading and CEL is back!! Will be getting it fixed soon hopefully.

On a side note would a side effect of this sensor not working be that the A/C blows only hot air. Or does this point to the thermostat. Cause when this first happened on the highway, I had the same hot air through the A/C vents. However when it started working again, it was nice and cool. Now hot air again

 

[Mounce]

Yeah, the way I understand it is that the AC adds a decent heat load to everything. If the computer doesn't know what the temperature is then it kills the AC as a precaution.

 

[$ Khalid ! 9130]

Yeah, the way I understand it is that the AC adds a decent heat load to everything. If the computer doesn't know what the temperature is then it kills the AC as a precaution.

Hence pointing once again to the Engine Coolant Temp Sensor right !

 

[Mounce]

Yezzir

 

[$ Khalid ! 9130]

Well back to this problem again and it seems the sensor is out of action. No reading at all since the past few days. Am having to drive with the windows down in this hot weather is killing me.....

I am going to try to remove and then reinstall the sensor, cause is there any possibility of it becoming loose??

Edit: Anyone have the part number for the sensor. Checked online and I am getting weird numbers which don't match my local parts guys database. Thanks as always

 

[Mooseman]

So you haven't replaced it yet? What are you waiting for man?

For part numbers, RockAuto is your friend.


The GM part is #12601050

I doubt very much just re-installing it will fix this. It could be a loose connection as it is intermittent.

 

[$ Khalid ! 9130]

So you haven't replaced it yet? What are you waiting for man?

For part numbers, RockAuto is your friend.
View attachment 80467

The GM part is #12601050

I doubt very much just re-installing it will fix this. It could be a loose connection as it is intermittent.

Nope, as you know just got back. Fell ill the past couple of days and am still recovering... . Thanks for the part number though will surely be getting to this by tmrw hopefully

 

[$ Khalid ! 9130]

Hi everyone, just an update I was planning to get down to this issue, today and while going trough the internet, I read that to remove the ECT sensor I would have to do a coolant flush. Is this absolutely necessary, as I am just planning to check for loose connections, before I actually buy a new sensor to put in the car. I also read up that GM changed its position to a really bad location. How have the experiences been with others changing their ECT on the newer design engines

 

[rizzo20]

I just replaced my sensor on my '08 this past weekend. I didn't do a system flush but I lost about 1/2 to 3/4 gallon of antifreeze once I removed the sensor. I just added antifreeze directly to the radiator after the sensor was replaced, took the caps of the radiator and overflow/reservoir tank, started the vehicle and let it come up to temp with both caps removed. I had to add a little while it was coming up to temp as the air displaced.

Also some tips, I took the passenger side inner fender out (easy) and went through the wheel well (with the tire off) and used a swivel/universal attachment on my 3/8" ratchet. I also took one of my old 15 mm deep well sockets and ground a slot in it to allow it to slip over the wires while installing the new one.

 

[$ Khalid ! 9130]

I just replaced my sensor on my '08 this past weekend. I didn't do a system flush but I lost about 1/2 to 3/4 gallon of antifreeze once I removed the sensor. I just added antifreeze directly to the radiator after the sensor was replaced, took the caps of the radiator and overflow/reservoir tank, started the vehicle and let it come up to temp with both caps removed. I had to add a little while it was coming up to temp as the air displaced.

Also some tips, I took the passenger side inner fender out (easy) and went through the wheel well (with the tire off) and used a swivel/universal attachment on my 3/8" ratchet. I also took one of my old 15 mm deep well sockets and ground a slot in it to allow it to slip over the wires while installing the new one.

Thanks for the clear up and great tip. Really appreciate it!

 

[Mooseman]

You can minimize the coolant loss by having the new sensor ready to go in one hand while removing the old one in the other hand. Working on a COLD engine, open the cap to relieve pressure, put it back on and pinch off the overflow tube. When you take out the sensor and coolant comes out, this will create a vacuum in the system, further minimizing coolant loss. After the install, open the cap, start the engine, top off the coolant, close the cap and add a bit extra in the overflow tank.

 

[AtlWrk]

Edit: Anyone have the part number for the sensor. Checked online and I am getting weird numbers which don't match my local parts guys database. Thanks as always

One thing I missed and haven't seen mentioned a lot around here is that in addition to the sensor being in a different location on 2006+ MYs, it is a different sensor than the older MYs, too. Amazon had the wrong data so I had the wrong sensor and didn't know it until I had the old one out, with wires cut and coolant pouring everywhere. I had no option but to make a mad dash to Autozone, covered in coolant, before they closed to get the right one.

To top it off, my issue was never the sensor--the new thermostat (AC Delco) I put in weeks before was bad out of the box.

 

[$ Khalid ! 9130]

Will keep that in mind. Thanks @Mooseman and @AtlWrk, but I guess I will get this done at a dealership, or one of AcDelco outlets as I have a general service due on the car so, will have to let them take care of it. Hopefully will get it done by today

 

[$ Khalid ! 9130]

Well took it to the dealership today, got quoted a price of 1200 SR ($320) for changing the whole thermostat and sensor. Would've had to leave the TB with them for 5-6 hrs. Told them thank you very much and left with the computer check done on my truck. This is the report I got:

 

[Mooseman]

Evap leaks are usually a bad gas cap, which was discussed.

Swap the #3 coil to #4 position and the other known good coil to #3. If the misfire moves to #4, then it's the coil. Start with that and we'll go from there.

 

[$ Khalid ! 9130]

Yep just changed that yesterday, I took enough pics maybe I should write an article . The misfire I know I can handle, but it's the P0128 that's bothering me. It's starting to get really hot in the day here and without AC I'm . The mechanic at the dealership said it has to be the thermostat and not the sensor. That makes me want to get an OBDII scanner, but am waiting on a guy who owes me money to purchase one

 

[Mooseman]

P0128, that's easy. It's the thermostat is stuck open as the engine is running too cool.

 

[$ Khalid ! 9130]

What would be the solution to that, change the thermostat??

 

[rizzo20]

P0128, that's easy. It's the thermostat is stuck open as the engine is running too cool.

If the temp sensor fails wouldn't that also create a P0128 and the T-stat could be good? I believe my T-stat was stuck open (operated at 176 f) and never once got a P0128.

 

[$ Khalid ! 9130]

As the code has many different things going bad, I am thinking it would be best to just replace the thermostat and the ECT sensor at the same time and hopefully finish the problem once and for all

 

[Mooseman]

Yes. At the time when the sensor was just above the thermostat on earlier models, when either failed, it was recommended to replace both as getting to them was a tough job.

Replace the sensor first since it's not in the same place and needs to be replaced anyway. If the temps are still low, replace the thermostat.

 

[$ Khalid ! 9130]

Just when I finally thought I had gotten to the bottom of the problem seems like there is no problem!!!




Everything is functioning normally, AC is back and working perfectly!!! This car is playing me, it's playing me good!!

 

[FearlessAZ]

I would replace both the thermostat and the sensor since you are already down there. no harm in replacing both.

Just because it doesn't work one day and works the next, does not mean it is fixed.

Both parts are cheap and easy to do yourself. I did both while doing my fan clutch and water pump. Fan clutch was already bad and having same issue with the temp gauge.