Why do the newer temp gauges read fake values?
11-24-2005, 11:40 AM
#21
TECH Enthusiast
Thread Starter
iTrader: (1)
Join Date: Nov 2004
Location: Ontario, Canada
Posts: 698
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by wait4me
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
11-24-2005, 11:54 AM
#22
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)...?
I believe what MPP means is if you tapped into the clusters harness and sent analog currents to the temp guage it'll give a reading, thus if you put in a 98 sensor in a 99+ and used the 3rd prong to tap into the cluster you could in theory have a functional guage.
On another note, if GM would not have chose to set the low speed cooling fan to come on at 226* they would not of had customers freaking out in traffic. 226*
11-24-2005, 03:17 PM
#25
TECH Senior Member
1999+ F-body:
the PCM reads ECT sensor and communicates the temp to the cluster as a message over the Class 2 serial bus;
so one, but not both, of the following must be true:
a. the PCM sends the correct temp as is and the cluster remaps it (makes it incorrect);
b. the PCM sends a remapped (incorrect) temp and the cluster displays it as is.
Which one of these is true...?
If a. is true, then the cluster firmware would have to be hacked to fix the temp.
If b. is true, then the PCM has either a table or a routine that remaps the temp to the incorrect value.
At present the only thing you can infer from the gauge reading is whether the engine was recently running,
and that makes the gauge petty much useless.
1998 F-body:
ECT sensor has a analog signal to PCM, and another analog signal to the gauge;
so either/or:
1. the ECT sensor outputs an incorrect value on the second wire,
2. the gauge is non-linear or otherwise skews its analog input.
Appears that 1. is true and you have to be lucky to have a correct ECT sensor.
98 owners could test if the gauge is linear by connecting a linear pot. (the variable resistance kind of pot...
) and seeing if the gauge responds linearly.
the PCM reads ECT sensor and communicates the temp to the cluster as a message over the Class 2 serial bus;
so one, but not both, of the following must be true:
a. the PCM sends the correct temp as is and the cluster remaps it (makes it incorrect);
b. the PCM sends a remapped (incorrect) temp and the cluster displays it as is.
Which one of these is true...?
If a. is true, then the cluster firmware would have to be hacked to fix the temp.
If b. is true, then the PCM has either a table or a routine that remaps the temp to the incorrect value.
At present the only thing you can infer from the gauge reading is whether the engine was recently running,
and that makes the gauge petty much useless.
1998 F-body:
ECT sensor has a analog signal to PCM, and another analog signal to the gauge;
so either/or:
1. the ECT sensor outputs an incorrect value on the second wire,
2. the gauge is non-linear or otherwise skews its analog input.
Appears that 1. is true and you have to be lucky to have a correct ECT sensor.
98 owners could test if the gauge is linear by connecting a linear pot. (the variable resistance kind of pot...
) and seeing if the gauge responds linearly. Last edited by joecar; 11-24-2005 at 03:30 PM.
