Could this be why? (98 Engine Temp Guage)
Could this be why? (98 Engine Temp Guage) As most of you know the 98 temp gauge is credited with being a slightly better piece of crap then the others due to better accuracy. I didnt ever know why and i couldnt ever find anything on it, until today. I had hit my coolent temp sensor with my header the other night when i removed it, i headed to autozone to get another and all they had listed was a 2 blade sensor, mine is a 3, no big deal, off to the dealership, same thing, no 3 blade sensor, they said that i needed to rewire the connector in order to fit the new sensor since the design was changed. Weird thing is the sensor was listed as a 2 blade for a 98 TA, after some more searching we found the 3 blade under a 98 ls1 camaro instead, a dollar more, but saves me rewireing hassle. So could this 3rd wire be the reason for better accuracy? Any idea's?
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From: South Alabama
The 98's had a true temperature gauge, problem was people kept seeing the temp fluctuate up and down as the thermostat opened and closed.
They would take the cars in to the dealership to have the "problem" repaired because they didn't understand what was going on.
Starting with the 99 model year they made the gauges all read 210 degrees when the coolant temperature fell in the range of 180-225 degrees so they would have less people bringing their autos in for correction of a non-issue. It saved them money on all the extra warranty service.
They would take the cars in to the dealership to have the "problem" repaired because they didn't understand what was going on.
Starting with the 99 model year they made the gauges all read 210 degrees when the coolant temperature fell in the range of 180-225 degrees so they would have less people bringing their autos in for correction of a non-issue. It saved them money on all the extra warranty service.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Originally Posted by 98NBM_TransAm
As most of you know the 98 temp gauge is credited with being a slightly better piece of crap then the others due to better accuracy. I didnt ever know why and i couldnt ever find anything on it, until today. I had hit my coolent temp sensor with my header the other night when i removed it, i headed to autozone to get another and all they had listed was a 2 blade sensor, mine is a 3, no big deal, off to the dealership, same thing, no 3 blade sensor, they said that i needed to rewire the connector in order to fit the new sensor since the design was changed. Weird thing is the sensor was listed as a 2 blade for a 98 TA, after some more searching we found the 3 blade under a 98 ls1 camaro instead, a dollar more, but saves me rewireing hassle. So could this 3rd wire be the reason for better accuracy? Any idea's?
TECH Veteran
Joined: Dec 2004
Posts: 4,012
Likes: 1
From: Beaumont, TX
Looks like it's gauge 'inaccurately' controlled by PCM, vs gauge with a third wire coming from the sensor. (On LT1s, they had two separate sensors: a 2-wire one for the PCM, located in the water pump housing; and a 1-wire one for the gauge, located in a cylinder head.)
Think these are the right numbers:
LS1 coolant temperature sensor (98) (3-wire sensor: 2 for PCM, 1 for gauge) = 12551708
LS1 coolant temperature sensor (AC-Delco #213-953) (99-02) (2-wire) = 15326388
Think these are the right numbers:
LS1 coolant temperature sensor (98) (3-wire sensor: 2 for PCM, 1 for gauge) = 12551708
LS1 coolant temperature sensor (AC-Delco #213-953) (99-02) (2-wire) = 15326388
Last edited by ACW; Nov 1, 2005 at 09:55 PM.
Joined: Nov 2001
Posts: 34,627
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From: Schiller Park, ILL Member: #317
Originally Posted by ACW
LS1 coolant temperature sensor (98) (3-wire sensor: 2 for PCM, 1 for gauge) = 12551708
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Verdad Gallardo not exactly i havent tried it yet but i got a mod form another member whos successfuly done this ... past the sensor swap ya gotta run a wire from the 3rd prong on the sensor to the gauge cluster and soider in a resistior to calibrate the gauge .. it seems pritty straight forward IF ANYBODY NEEDS THE INSTRUCTIONS I CAN FORWARD THEM TO YOU ALONG WITH PICS OF THIS MOD JUST SEND ME AN E-MAIL my holdup was i never fond a 3 prong sensor that would fit in the hole all of the 3 prong sensors i was able to track down were way to big to threads up to the 2 prong sensor's hole and i didnt feel like tapping the block to resolve this BUT IF THERE IS A STOCK SIZED 3 PRONG SENSOR ID DO THIS MOD TODAY..
Originally Posted by RPM WS6
98NBM_TransAm.....is this the same number you got from the dealer for the correct '98 sensor? Thanks.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Originally Posted by 98NBM_TransAm
Yea the part number 12551708 is the right one, i lost the reciept and just found it again, sorry for the delay
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Joined: Dec 2004
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From: Beaumont, TX
Originally Posted by Jpr5690
not exactly i havent tried it yet but i got a mod form another member whos successfuly done this ... past the sensor swap ya gotta run a wire from the 3rd prong on the sensor to the gauge cluster and soider in a resistior to calibrate the gauge .. it seems pritty straight forward IF ANYBODY NEEDS THE INSTRUCTIONS I CAN FORWARD THEM TO YOU ALONG WITH PICS OF THIS MOD JUST SEND ME AN E-MAIL my holdup was i never fond a 3 prong sensor that would fit in the hole all of the 3 prong sensors i was able to track down were way to big to threads up to the 2 prong sensor's hole and i didnt feel like tapping the block to resolve this BUT IF THERE IS A STOCK SIZED 3 PRONG SENSOR ID DO THIS MOD TODAY..
Staging Lane
Joined: Dec 2004
Posts: 99
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From: Chesapeake, VA
Thanks for the info. I have been going nuts trying to find this sensor but all of the parts stores are baffled also. My fan has stopped running unless the A/C is running so I have been trying to change the sensor hoping that will fix the problem. The guage operates fine though. If anyone else has run across this problem, please fill me in to the cause.
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Joined: Dec 2004
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From: Beaumont, TX
Originally Posted by Jpr5690
email sent
https://ls1tech.com/forums/general-maintenance-repairs/406399-temperature-gauge-mod-instructions.html 
nope not true... never saw another temp sensor on the other head... and by the way... what If I don't install this sensor would it affect the ecu's operation? because I already have another Sensor that tells the fan when to start and when to stop... will I be needing it?
