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Discussion Starter #1
Well, this didn't take long. :cry:

Just bought this 2003 9-5 Aero with 28k miles on it a month or two ago. Noticed this morning that during my entire 45 minute commute to work, my temperature gauge never moved from cold. Normally it will go to the 7:30 or 8:00 position and stay there, but today, it never moved from the very bottom. Any ideas?

Good thing I bought the extended warranty. :cry:
 

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Search is your friend. This exact topic has been covered repeatedly over the last few weeks. Either the coolant temp sensor is faulty or the thermostat is stuck open. Both are easy fixes.
 

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Discussion Starter #3
Perhaps. It still makes me feel better to vent though. :D

The car is obviously under warranty. Should I have them fix it instead?
 

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Discussion Starter #5 (Edited)
Well the temp gauge seemed to be working again this morning, when suddenly the check engine light came on and the needle died again (shot straight to cold) while driving to work. I drove straight to the dealer before work and am currently sporting a Mazda5 rental until it's fixed. :x
 

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Did you manage to get this issue fixed? I have had the issue for over a year, and and the same time the tachometer (rev gauge) also drops to zero, and I get the CEL.

Recently, the car has decided to refuse to hot restart after this issue occurs (but works when left for a while).

In an attempt to fix, I have replaced:

* Main instrument unit (MIU) in the dashboard
* DI cartridge (which I found had been recalled)
* Temp sensor

And nothing has fixed it. To say I am frustrated with this would be an understatement. It has cost over $1000 and is no closer to being fixed.

I am wondering now if it could be a problem with the either ECU (Trionic) or TWICE module, or perhaps a wiring problem. The problem is that all of the mechanics I have talked to (and I have tried a few) refuse to accept that it could be a wiring problem (I suspect because of the difficulty of finding such a problem), yet they are unable to find the problem.
 

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Discussion Starter #7
The dealer was very polite about the whole thing...it was simply a malfunctioning thermostat which was easily replaced. I had my car back within 5 hours with no problems since (knock on wood).

I'm sorry to hear about your many problems...thankfully the only thing malfunctioning was the thermostat (which triggered the CEL). Best of luck to you.
 

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Discussion Starter #8 (Edited)
Apparently I didn't knock on wood hard enough becase less than 3 months later, the problem has resurfaced. What the hell is causing this? On a 2003 Saab with 33k miles, I wouldn't expect to have these kinds of problems.
 

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edwardforgacs said:
In an attempt to fix, I have replaced:

* Main instrument unit (MIU) in the dashboard
* DI cartridge (which I found had been recalled)
* Temp sensor
Zachmaster said:
The dealer was very polite about the whole thing...it was simply a malfunctioning thermostat which was easily replaced. I had my car back within 5 hours with no problems since (knock on wood).
I have this problem right now (Not getting up to temp). I figgure the problem could be two things - the thermo being stuck open, or the coolant temperature sensor has failed. That's why I'll be replacing both of them at the same time.

Zach - Bring your reciept and you vehicle back to the guys that tried to fix it - and suggest that they fix both parts this time at no charge. The coolant temp sensor is a cheap ($15) part and easy to fix...
 

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This could be something else, cause I have this exact problem and I put a new sensor in and it didn't do anything. My mechanic thinks it might be a faulty dashboard module.
 

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There's nothing wrong with the temperature of my car, when the gauge is working.
 

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Discussion Starter #13
I called the dealer to verify what exactly they replaced a few months ago. They replaced my engine coolant temperature sensor, not my thermostat. The problem vanished up until today. I apologize for the misunderstanding. How difficult is this part to replace by an average joe such as me?
 

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Discussion Starter #14
In addition, I've noticed that since my temperature gauge was not moving from cold during the trip to work this morning, it has worked fine for the 2 errand trips I've taken since this morning. :confused:

Is there a connection or something that could be loose?
 

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I had this issue of the temp gauge only rising to 7:30 - 8, then it would drop to the bottom. I replaced the temp sensor and it seemed to work for a short time and went right back to it. It seemed that the colder the morning, the more likely my temp gauge would bottom out.

I drove it like this for almost a yr til one lovely summer morning driving to work, got all kinds of lights and warning bells and noticed my temp gauge was right to the top of the gauge. No steam, no wierd noises, so i coasted to the side of the highway and got out to check it out. Not steam or antifreeze smell, belts in place.

Got back in and started it up, temp gauge had dropped a bit and since i was only a couple miles to my saab indy, choose to limp my way there. I'd drive til the temp gauge got close to the red and then i pulled over, shut it off and let it cool down for 10 mins. Then drive another 1/2 mile and repeat.

By this point i was pretty sure it was the thermostat that stuck shut.
Indy tested and replaced the thermostat and my temp gauge has been fine since. It has never warmed up so fast since i bought the car 1.5 yrs earlier.

There was a thread that explained if the engine did not reach operating temp after 15 mins, the gauge will drop to zero. I think that the system still monitors the coolant temp and only throws a cel if the coolant temp drops too low or goes too high.

Once the engine is warm and you shut it off and restart, the gauge is reset and since the coolant temp is at or close to operating temp, the gauge functions normally.

zachmaster, get them to replace the thermostat like they should have done originally.
 

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luv2drinkcoke said:
There was a thread that explained if the engine did not reach operating temp after 15 mins, the gauge will drop to zero. I think that the system still monitors the coolant temp and only throws a cel if the coolant temp drops too low or goes too high.

Once the engine is warm and you shut it off and restart, the gauge is reset and since the coolant temp is at or close to operating temp, the gauge functions normally.
Whaaaaa, where is this thread? :confused:
 

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I went reading up on this. I didn't see anything about the gauge resetting. The WIS says that if the Coolant temp sensor has some sort of voltage malfunction, a substitute value of 90 deg C is substituted.

I don't know where that would read on the coolant temp gauge though...

Also, for Coolant Temp gauge faults there are 5 CEL codes:
0115 - performance problem
0116 - temerature value implausable
0117 - voltage too low
0118 - voltage too high
0119 - unfeasable changes in sensor voltage
 

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This was not the thread i remember reading, but after 2 days of searching for it, best i can do.

Subject: Coolant Gauge Drops With DTC P0116 Setting in a Saab 9-5

Models:
1999-2005 Saab 9-5 Sedan
1999-2005 Saab 9-5 Wagon

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

CONDITION/CONCERN:
A technician may find an intermittent check engine light on and coolant temperature gauge drops to cold while driving. There are usually no concerns of loss of heater performance, although it is possible. T7 ECM stores DTC p0116 for coolant temperature sensor performance.


RECOMMENDATION/INSTRUCTIONS:
Have technician replace the engine coolant thermostat. If T7 ECM detects the engine coolant takes to long to heat up, it will set p0116 and MIU will command the temperature gauge to cold.

Al, it's not a temp sensor issue. The sensor is working fine. It's the coolant temp takes too long to warm up and the gauge is programmed to drop to cold.
As we have seen, if your temp gauge drops to cold and you turn off your engine. On restart, the gauge appears to work properly. The program which tells it to drop to cold, is reset. I would assume that if the engine temp again did not reach the programs min engine temp, it would drop to cold again.
The cel is intermittent for this problem, as an indy told me the fault would have to happen 3 consecutive times before a cel is generated.
 

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Any updates on which parts fixed the temp gauge problem?
Is it the engine coolant thermostat?
I was driving to Boston today and the temp gauge droped to bottom. I pulled over, retarted and the temp gauge seemed to went up fine but few minutes later, it dropped again and CEL came on. I pulled over again, pulled the pin17 for few minutes and the problem seems to have disappeared for the last 150miles.

Thanks!
 
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