Circuit Description
The engine coolant temperature (ECT) sensor monitors the temperature of the
coolant. This input is used by the powertrain control module (PCM) for engine control,
and as an enabling criteria for some diagnostics.
The air flow coming into the engine is accumulated and used to determine if
the vehicle has been driven within the conditions that would allow the engine coolant
to heat up normally to the Closed Loop temperature. If the coolant temperature does
not increase normally or does not reach Closed Loop temperature, the diagnostics
that use engine coolant temperature as enabling criteria may not run when expected.
This DTC will only run once per ignition cycle within the enabling conditions.
If the PCM detects the calibrated amount of air flow and engine run time have been
met and the ECT has not met the Closed Loop temperature, DTC P0125 sets.
Step
| Action
| Values
| Yes
| No
|
Schematic Reference:
Engine Controls Schematics
Connector End View Reference:
Engine Controls Connector End Views
or
Powertrain Control Module (PCM) Connector End Views
|
1
| Did you perform the Diagnostic System Check-Engine Controls?
| --
| Go to
Step 2
| Go to
Diagnostic System Check - Engine Controls
|
2
|
ImportantThe cooling fans are commanded ON when certain
engine coolant temperature (ECT) DTCs are set.
Is the cooling system coolant low?
| --
| Go to
Draining and Filling Cooling System
in
Engine Cooling
| Go to
Step 3
|
3
| Test and verify the proper operation of the thermostat. Refer to
Thermostat Diagnosis
in Engine Cooling.
Did you find and correct the condition?
| --
| Go to
Step 14
| Go to
Step 4
|
4
|
- Disconnect the ECT sensor.
- Inspect for the following conditions:
- Corrosion on the ECT sensor terminals
- Improper or corroded terminals at the ECT harness connector
- Loose terminals in the ECT harness connector--Refer to
Testing for Intermittent and Poor Connections
and
Connector Repairs
in Wiring Systems.
Did you find and correct the condition?
| --
| Go to
Step 14
| Go to
Step 5
|
5
| Measure the voltage from the signal circuit of the ECT sensor to a good ground
with a DMM. Refer to
Circuit Testing
in Wiring
Systems.
Is the voltage within the specified range?
| 4.8-5.2 V
| Go to
Step 6
| Go to
Step 8
|
6
| Measure the voltage from the signal circuit of the ECT sensor to the low reference
circuit of the ECT sensor with a DMM. Refer to
Circuit Testing
in Wiring Systems.
Is the voltage within the specified range?
| 4.8-5.2 V
| Go to
Step 9
| Go to
Step 7
|
7
| Test the ECT sensor low reference circuit for high resistance. Refer to
Circuit Testing
and
Wiring Repairs
in Wiring Systems.
Did you find and correct the condition?
| --
| Go to
Step 14
| Go to
Step 11
|
8
| Test the ECT sensor signal circuit for high resistance. Refer to
Circuit Testing
and
Wiring Repairs
in Wiring Systems.
Did you find and correct the condition?
| --
| Go to
Step 14
| Go to
Step 11
|
9
|
- Turn OFF the ignition.
- Remove the ECT sensor. Refer to
Engine Coolant Temperature (ECT) Sensor Replacement
.
- Place the sensor on a work surface away from any heat source.
- Allow the sensor to reach the ambient air temperature for 30-60 minutes.
- Observe and record the ambient air temperature of the vehicle environment
using an accurate thermometer.
ImportantDo not hold the ECT sensor by the probe.
- Measure the resistance of the ECT sensor and record the value.
- Compare the resistance measurement of the ECT sensor to the ambient air
temperature on the Temperature vs. Resistance table. Refer to
Temperature vs Resistance
.
Is the resistance measurement of the ECT sensor within the specified range?
| --
| Go to
Step 10
| Go to
Step 12
|
10
| Install the ECT sensor. Refer to
Engine Coolant Temperature (ECT) Sensor Replacement
.
Is the action complete?
| --
| Go to
Intermittent Conditions
| --
|
11
| Test for an intermittent and for a poor connection at the powertrain control
module (PCM). Refer to
Testing for Intermittent and Poor Connections
and
Connector Repairs
in
Wiring Systems.
Did you find and correct the condition?
| --
| Go to
Step 14
| Go to
Step 13
|
12
| Replace the ECT sensor. Refer to
Engine Coolant Temperature (ECT) Sensor Replacement
.
Did you complete the replacement?
| --
| Go to
Step 14
| --
|
13
| Replace the PCM. Refer to
Powertrain Control Module (PCM) Replacement
.
Did you complete the replacement?
| | Go to
Step 14
| --
|
14
|
- Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may
also operate the vehicle within the conditions that you observed from the Freeze
Frame/Failure Records.
Did the DTC fail this ignition?
| --
| Go to
Step 2
| Go to
Step 15
|
15
| Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?
| --
| Go to
Diagnostic Trouble Code (DTC) List
| System OK
|
