DTC P0118 Engine Coolant Temperature
(ECT) Sensor Circuit High Voltage
The Engine Coolant
Temperature (ECT) sensor contains a semiconductor device which changes the
resistance based on the temperature (a thermistor).
The ECT sensor is mounted in the left bank cylinder head near the front of the
engine. The ECT sensor has a signal circuit and a ground circuit. The PCM
applies a voltage (about 5.0 volts) on the signal circuit to the sensor.
The PCM monitors the changes in this voltage caused by changes in the
resistance of the sensor in order to determine the coolant temperature.
When the coolant is
cold, the sensor (thermistor) resistance is high. The
PCMs signal voltage is only pulled down a small amount through the sensor to a
ground; therefore, the PCM senses a high signal voltage (low temperature). When
the coolant is warm, the sensor resistance is low. The signal voltage is pulled
down a greater amount; therefore, the PCM senses a low signal voltage (high
temperature). At normal operating temperature, the voltage should measure about
1.5-2.0 volts at the PCM.
When
the PCM senses a signal voltage higher than the normal operating range of the
sensor, this DTC sets.
Conditions
for Running the DTC
The engine run time is
greater 60 seconds.
Conditions
for Setting the DTC
- The Engine Coolant Temperature is
less than -39°C (-38°F).
- All conditions met for 20 seconds.
Action
Taken When the DTC Sets
- The PCM illuminates the malfunction
indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.
- The PCM records the operating
conditions at the time the diagnostic fails. The first time the diagnostic
fails, the PCM stores this information in the Failure Records. If the
diagnostic reports a failure on the second consecutive ignition cycle, the
PCM records the operating conditions at the time of the failure. The PCM
writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the malfunction
indicator lamp (MIL) after 3 consecutive ignition cycles that the
diagnostic runs and does not fail.
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC clears after
40 consecutive warm-up cycles, if no failures are reported by this or
any other emission related diagnostic.
- Use a scan tool in order to clear
the MIL and the DTC.
Important
- Remove any debris from the PCM connector surfaces
before servicing the PCM. Inspect the PCM connector gaskets when
diagnosing/replacing the PCM. Ensure that the gaskets are installed
correctly. The gaskets prevent contaminate intrusion into the PCM.
- For any test that requires probing the PCM or component
harness connectors, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents any damage to the harness connector terminals.
- The following may cause an
intermittent:
- Poor Connections
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- If the engine has sat overnight, the
engine coolant temperature and intake air temperature values should
display within a few degrees of each other. If the temperatures are not
within 3°C (5°F), refer to Temperature vs Resistance .
- If you determine that the DTC occurs
intermittently, performing the P1115 diagnostic table may isolate the
cause of the fault.
- For an intermittent, refer to Symptoms
.
The numbers below refer
to the step numbers on the diagnostic table.
- This step determines
if the malfunction is present. For any test that requires probing the PCM
or a component harness connector, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents damage to the harness connector terminals.
- Disconnecting the
PCM allows using the DMM J 39200 in
order to test continuity of the circuits. This aids in locating an open or
a shorted circuit.
- Disconnecting the
PCM allows using the DMM J 39200 in
order to test continuity of the circuits. This aids in locating an open or
a shorted circuit.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
Is
the ECT sensor at the specified value? |
-39°C (-38°F) |
|||
Does
the scan tool indicate that this diagnostic failed this ignition? |
-- |
Go to Diagnostic Aids |
||
Is
the ECT sensor at the specified value? |
140°C (284°F) |
|||
|
Jumper
the ECT sensor signal circuit to a known good ground. Is the ECT sensor at
the specified value? |
140°C (284°F) |
|||
Is
the ECT sensor signal circuit open? |
-- |
|||
|
Repair
the ECT sensor signal circuit. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
Is
the ECT sensor ground circuit open? |
-- |
|||
|
Replace
the ECT sensor. Refer to Engine
Coolant Temperature (ECT) Sensor Replacement . Is the action complete? |
-- |
-- |
||
|
Repair
the ECT sensor ground circuit. Refer to Wiring
Repairs in Wiring Systems. Is the action complete? |
-- |
-- |
||
Did
you find and correct the condition? |
-- |
|||
Did
you find and correct the condition? |
-- |
|||
|
Important: Program the replacement
PCM. Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |