P0125
Symptom: The CHECK ENGINE lamp (MIL) is on.
Coolant temperature, slow increase
Symptom of fault
The CHECK ENGINE lamp (MIL) is on.
Conditions
Engine running. Vehicle speed >20 km/h. The coolant temperature does not rise by
20°C (36°F) from starting temperature or reach 40°C 104°F) within 6
minutes and 40 seconds.
Diagnostic help
The diagnostic trouble code may be generated as a result of:
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connection of a non-approved
external parking heater
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ice formation in the cooling system
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a fault in the coolant temperature sensor or its circuit
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Checking the wiring. Intermittent faults may occur as a result of occasional short
circuits and breaks in the wiring. Jiggle the leads and in-line connectors at several places and
in different directions to reveal faults in the wiring harness. Observe the multimeter, ISAT scan
tool or test lamp while carrying out this check.
Diagnostic procedure
1. Check the anti-freeze
At ambient temperatures below 0°C (32°F), check the freezing point of
the coolant.
Is the freezing point OK?
Continue with point 2.
Rectify the fault and proceed to point 4.
2. Check the thermostat
The engine should be cold enough to allow a hand to be placed on the cylinder
head without discomfort.
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Connect an ISAT scan tool and
contact the ICE.
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Select
"READ FUNCTIONS".
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Select
"COOLANT TEMPERATURE".
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Start the engine and warm it up at
idling speed. Feel the upper radiator hose, near the thermostat, to check that it quickly
becomes hot when the coolant reaches a temperature of about 89°C (192°F) and
the thermostat opens.
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Following this, the coolant temperature should remain fairly constant at about
89°C (192°F) for a minute or so.
Is the thermostat OK?
Continue with point 3.
Change the thermostat and proceed to point 4.
3. Check the coolant temperature
sensor
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Engine running at idling
speed.
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Connect an ISAT scan
tool.
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Contact the Trionic
system.
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Select
"READ FUNCTIONS".
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Select
"COOLANT TEMPERATURE".
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Select
"READ FUNCTIONS".
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Select
"COOLANT TEMPERATURE".
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The difference between the two temperature readings should not be more than
5°C (9°F).
Are the readings OK?
Continue with point 4.
See fault diagnosis for diagnostic trouble codes P0115, P0117 and P0118.
4. Final check
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Clear the diagnostic trouble
code
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Implementation of driving cycle:
Warm up the engine at idling speed until the radiator fan cuts in.
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Evaluation of driving
cycle:
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Unplug the temperature
sensor's connector from the ICE so that the radiator fan will run
continuously
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Check that the coolant temperature in the Trionic system drops to and stabilizes
at about 89°C (192°F)
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Is the function OK?
Proceed to
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The remedial measure taken was correct.
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Connect the temperature
sensor to the ICE.
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Clear the diagnostic trouble code
for the temperature sensor in the ICE.
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