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Re: Replaced temp sensor & thermostat, P0125 persists Posted by sam96CS [Email] (#852) [Profile/Gallery] (more from sam96CS) on Fri, 30 Aug 2013 21:05:42 In Reply to: Replaced temp sensor & thermostat, P0125 persists, JerseySaab [Profile/Gallery] , Fri, 30 Aug 2013 10:09:32 Members do not see ads below this line. - Help Keep This Site Online - Signup |
According to the Trionic service manual for model years 1996- P0125 is not caused by the failure to reach a certain temperature. Rather, it is caused by the failure to warm up rapidly enough. The manual describes a P0125 as "coolant temperature, slow increase". Code scanners that report "insufficient coolant temperature" are misleading because they don't include the time element.
Conditions when a P0125 code is set:
Engine running.
Vehicle speed greater than 12 mph.
Within 6 minutes and 40 seconds the coolant temperature either does not rise by 36 degrees F from the starting temperature or fails to reach 104 degrees F.
Per the same manual, temperature sensor resistance at various temperatures in kohms
Temp kohms
-22F 20-30
-14F 7.0-11.4
+68F 2.1-2.9
+104F 1.0-1.3
+140F 0.565-0.670
+176F 0.295-0.365
+194F 0.24-0.26 (the Haynes manual says 24 to 26 ohms)
+230F 0.14-0.16 (the Haynes manual says 14 to 16 ohms)
I think the error is in the Haynes manual.
The hotter it gets, the less resistance at the sensor. The cooling system is designed to warm up rapidly to 192 degrees F at which point the thermostat opens and from then on maintains a fairly constant temperature at or near 192 F.
According to the Haynes manual the 1995 model cooling fan should not turn on until the temperature reaches 212 F. I don't know if it is the same for the 1997 model, but yours is turning on at a lower temperature, isn't it? Is it turning on so soon that the coolant does not warm up rapidly enough?
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