themperature gage descrepency

[vault]

I've been undergoing some cooling system issues (radiator/water pump replaced due to leaks). My in dash temperature gauge still has been reading high and floating between 196 and 208. I just hooked up GMTD scan and watched the temperature reading it was receiving. When my temp gauge in the dash was reading 196 the GMTD scan read 179-180 when the in dash gauge read 208-210 the GMTD read 185-187 watched it go thru these cycles serveal times and the reading were very consistent with no time lag. Is this a bad gauge, sending unit or something else?

[THEFERMANATOR]

Most likely a bad sending unit for the guage(the one in the drivers side cylinder head). Teh factory guage is not very accurate though even when working properly. I've found that the 160(first mark) on mine is actually only 100, the mark in between 160 and 210 is right about 175-180, but 210 reads pretty close to dead on actual.

[vault]

Thank you for your reply do you know If the gauge and the GMTDscan are getting the readings from the same sending unit?

[THEFERMANATOR]

Thank you for your reply do you know If the gauge and the GMTDscan are getting the readings from the same sending unit?

No, the guage gets its reading from the sender in the drivers side head and the ECM recieves its signal from the sensor in the T-stat housing.

[DmaxMaverick]

No, the guage gets its reading from the sender in the drivers side head and the ECM recieves its signal from the sensor in the T-stat housing.......and they can vary by that much, and more.

It is not uncommon, at all, to see the gage/PCM temp differentials such as this. More extreme weather temps can cause a greater spread. It's a matter of too much information, and not necessarily inaccurate instrumentation. Although many, if not most, vehicle instrumentation is not exact, they are close enough to track trends, which is the purpose of them, primarily.

[vault]

I was getting worried because according to the gauge my truck has been running hotter and hotter over the past months. Then when I checked with the scan software If the difference was correct (17-23 degrees) a few months ago when the gauge was consistently reading 180-85 then the coolant temp would have been 160ish which would be impossible.

[ajg6989]

on mine it reads hotter in the winter time and cooler in the summer but usually around 210 to 220 and when the turbo comes on it drops about five degrees and with the air on it drops about 2 degrees and the heat about one degree. I checked everything and the temps are 177 on the radiator side of the t stat and 198 on the engine side of the t stat.