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P0125 Severity
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
In order for the Powertrain Control Module (PCM) to maintain efficient fuel economy and minimize the emissions output from a vehicle, the engine cooling system must reach a critical operating temperature. This temperature, typically between 160-170 degrees, must be reached within 15 minutes after engine startup. If the weather is extremely cold, the coolant temperature must rise at least 70+ degrees starting temperature. If the coolant temperature does not reach operating temperature, or the temperature wanders excessively from this temperature, the PCM can't accurately and efficiently control fuel economy and emissions. The PCM will set code P0125.
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OBD-II Code P0125 is defined as a Insufficient Coolant Temperature For Close Loop Fuel Control
What does this Mean?
In order for the Powertrain Control Module or PCM to effectively control the fuel and ignition systems while, at the same time, minimize the emissions output from a vehicle, the engine cooling system must reach a critical operating temperature. This temperature is typically between 160-170 degrees F and must be reached within 15 minutes after a 'stone cold' start. If the weather is extremely cold, say 10 or more degrees below zero, the coolant temperature must rise at least 70+ degrees from the 'stone cold' starting temperature. A 'stone cold' start is achieved when the vehicle is started after sitting with its engine off for at least 8 consecutive hours. If the coolant temperature stays below the 160-170 degree range or wanders above and below this level, the PCM can't rely on the exhaust oxygen feedback data it receives from the oxygen sensors in the exhaust system. When this occurs, the PCM must rely on a crude 'limp home' type of fuel and ignition control program. This raises the level of exhaust gas pollution to unacceptably high levels and will trigger the check engine light.
Here's how to diagnose the P0125 code:
When doing the P0125 diagnosis, be sure to verify that either the electric or mechanical cooling fan is not stuck on because this will cause the engine to run at a very reduced operating temperature. Also, be sure to verify that the Intake Air Temperature Sensor readings are within reason, meaning that they are not too hot or too cold in relation to the outside air temperature and under-hood air temperature. A good rule of thumb is that the Intake Air Temperature reading is usually about 100º F below the Coolant Temperature readings after warm up. When cold starting the vehicle, the readings should begin at nearly identical values.