Why do the newer temp gauges read fake values?
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Why do the newer temp gauges read fake values? If I understand correctly, the gauge cluster reads a serial data stream to make the gauges read something. The temp gauge is simply displaying what its told to is it not? If this is correct, could a rewrite to the OS simply eliminate the code that gives the fake data? It sounds like deleting a subroutine and passing a variable unaltered. Does anyone know?
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99+ temp gauges are dummy guuges.... only reason I can think of is GM had too many people getting worried when the gauge would rise on a hot day past normal....
I talked about this w/my dad (Jaguar mechanic) a few years back and he stated that Jaguar did the same thing a while back because they were getting too many people coming in that were worried that the car may be overheating .... so in that situation they changed the temp gauges to "warming up, operating temp, overheating" ...
98 is the only year that's accurate (for f-bodies)
I talked about this w/my dad (Jaguar mechanic) a few years back and he stated that Jaguar did the same thing a while back because they were getting too many people coming in that were worried that the car may be overheating .... so in that situation they changed the temp gauges to "warming up, operating temp, overheating" ...
98 is the only year that's accurate (for f-bodies)
Originally Posted by horist
99+ temp gauges are dummy guuges.... only reason I can think of is GM had too many people getting worried when the gauge would rise on a hot day past normal....
I talked about this w/my dad (Jaguar mechanic) a few years back and he stated that Jaguar did the same thing a while back because they were getting too many people coming in that were worried that the car may be overheating .... so in that situation they changed the temp gauges to "warming up, operating temp, overheating" ...
98 is the only year that's accurate (for f-bodies)
I talked about this w/my dad (Jaguar mechanic) a few years back and he stated that Jaguar did the same thing a while back because they were getting too many people coming in that were worried that the car may be overheating .... so in that situation they changed the temp gauges to "warming up, operating temp, overheating" ...
98 is the only year that's accurate (for f-bodies)
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I annoyed at it like everyone else. I would like to know if the ramp upward during warm up is half real or fake too. All that to say, what creates the fake reading, the gauge cluster itself (I doubt it). Or is it fake data from the PCM in which case it should be fixable?
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Verdad Gallardo TECH Senior Member
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From: Lake Zurich, IL
^^^ nope... unless i'm mistaken.. 98 sensors are 3 prong with 1 feed going to the gauge cluster... 99+ are 2 prong with all feeds going to the PCM and the temp gauge fed off the serial bus...
if you want an accurate gauge best bet is an aftermarket water temp gauge
if you want an accurate gauge best bet is an aftermarket water temp gauge
yeah thats right, i remember my napa had a 3 prong listed for fbodies.
and yeah, i got an autometer one on the other head, great way to make sure both heads stay cool too
and yeah, i got an autometer one on the other head, great way to make sure both heads stay cool too
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All the research I have done indicates that it's the PCM that is making the coolant gauge act like an idiot light. I have sent coolant messages on the J1850 bus to two different gauge clusters (one T/A & one Camaro) and the temp gauge displays the analog coolant temp I'm sending it correctly.
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Originally Posted by MPP
All the research I have done indicates that it's the PCM that is making the coolant gauge act like an idiot light. I have sent coolant messages on the J1850 bus to two different gauge clusters (one T/A & one Camaro) and the temp gauge displays the analog coolant temp I'm sending it correctly.
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Originally Posted by joecar
So does this mean there might be a table in PCM flash for calibrating the temp data values sent to the gauge cluster (on 2000+ F-body)...?
My original '98 ECT temp sensor was off a bit. I complained to the dealer and they adjusted the dash to read 210* when the Tech II said 210*. I had the sensor replaced later, but before the warranty expired, and it remained accurate.
This past spring I blew a head gasket, and one of the things they replaced was the ECT sensor (I don't recall the reason). So now I've got that frickin idiot gauge also.
While the shop has LS1-Edit, they had no reason to modify the calibration.
This past spring I blew a head gasket, and one of the things they replaced was the ECT sensor (I don't recall the reason). So now I've got that frickin idiot gauge also.
While the shop has LS1-Edit, they had no reason to modify the calibration. 
I am very interested in hearing more of how you have an idiot 98 gauge now, what parts did they install?
While my 98 TA needle reads lower than the real temp is as well, it is linear off by about 10 degrees.
Ryan
While my 98 TA needle reads lower than the real temp is as well, it is linear off by about 10 degrees.
Ryan
The invoice lists GM P/N 12551708 as the coolant temp sensor for a 98 F-body. When I advised the shop the gauge was now off whereas it was correct before, they basically said they're all inaccurate and if mine was accurate before, then I was lucky.
Deg C When Coolant temperature falls below this value, the engine cold indicator is set.
Deg C When Coolant temperature rises above this value, the engine cold indicator is cleared.
Deg C When Coolant temperature falls below this value, the engine hot indicator is cleared.
Deg C When Coolant temperature rises above this value, the engine Hot indicator is Set.
Those are the only references in the whole bin file about a coolant temp gauge setting for the 99 up ls1/ls2
Deg C When Coolant temperature rises above this value, the engine cold indicator is cleared.
Deg C When Coolant temperature falls below this value, the engine hot indicator is cleared.
Deg C When Coolant temperature rises above this value, the engine Hot indicator is Set.
Those are the only references in the whole bin file about a coolant temp gauge setting for the 99 up ls1/ls2
I have all the pcms mapped out start to finish.