DTC P0128 (LDD)
Diagnostic Instructions
DTC Descriptor
DTC P0128 00: Engine Coolant Temperature (ECT)
Below Thermostat Regulating Temperature |
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
ECT Sensor 1 Signal
|
P0117 00
|
P0118 00
|
P0118 00*
|
P0116 00, P0128 00
|
Low Reference
|
-
|
P0118 00
|
P0118 00*
|
P0128 00
|
*ECM or sensor damage may occur if the circuit is shorted to
B+
|
|
|
Typical Scan Tool Data
ECT Sensor 1
Circuit
|
Short to Ground
|
Open
|
Short to Voltage
|
Operating Conditions: Engine operating
in closed loop
Parameter Normal Range: Varies with
coolant temperature
|
ECT Sensor 1 Signal
|
150°C (302°F)
|
-40°C (-40°F)
|
-40°C (-40°F)
|
Low Reference
|
-
|
-40°C (-40°F)
|
-40°C (-40°F)
|
|
|
Circuit/System Description
The engine control module (ECM) monitors the temperature of the
engine coolant for engine control and as an enabling criteria for
some diagnostics. The amount of air flow into an engine is
proportional to the amount of heat an engine generates. The ECM
monitors the amount of air flow into the engine to calculate engine
coolant temperature (ECT). The ECM uses the calculated temperature
to determine if the engine has warmed up to the thermostat
regulating temperature. If the coolant temperature does not
increase normally or does not reach the thermostat regulating
temperature, diagnostics that use the ECT as enabling criteria, may
not run when expected. If the engine coolant temperature fails to
reach the thermostat regulating temperature, before a predetermined
amount of air flow enters the engine, the DTC sets.
Conditions for Running the DTC
• |
DTCs P0112 00, P0113 00, P0116
00, P0117 00, or P0118 00 are not set. |
• |
The start-up ECT sensor 1 is
between -20 to +75°C (-4 to +167°F). |
• |
The calculated airflow into
the engine is greater than 11 g/s. |
• |
The engine run time is between
20 s and 23 min. |
• |
The thermostat commanded duty
cycle is less than 50%. |
• |
The DTC runs once per ignition
cycle when the above conditions are met. |
Conditions for Setting the DTC
The ECM detects that the amount of time it takes for the ECT
sensor 1 to reach maximum temperature has exceeded a calibrated
time.
Action Taken When the DTC Sets
DTC P0128 00 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0128 00 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
2. |
Ignition ON, observe the DTC
information with a scan tool. DTCs P00B7 00, P0597 00, P0598 00,
P0599 00, or P2181 00 should not be set. |
3. |
Engine idling for 15 min with
the A/C OFF. |
|
Note: Depending on
ambient temperature, it may take up to 4 min for the temperatures
to equalize.
|
4. |
Command the Engine Coolant
Thermostat Heater to 0% with a scan tool. Increase the engine speed
to 3 000 RPM. Observe the scan tool ECT Sensor 1 parameter. The
temperature should increase to greater than 102°C
(215°F). |
⇒ |
If less than the specified value, replace the E41
Engine Coolant Thermostat Heater. |
5. |
Command the E41 Engine Coolant
Thermostat Heater to 100% with a scan tool. Increase the engine
speed to 3 000 RPM. Observe the scan tool Radiator Coolant
Temperature Sensor and the ECT Sensor 1 parameters. The Radiator
Coolant Temperature Sensor and the ECT Sensor 1 parameters should
be within 20°C (68°F). |
6. |
Engine idling, observe the DTC
information with a scan tool. DTC P0128 00 should not set.
|
7. |
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 data. |
Circuit/System Testing
1. |
Ignition OFF, disconnect the
harness connector at the B34 Engine Coolant Temperature
Sensor. |
2. |
Ignition OFF for 1 min, test
for less than 5 Ω between the low reference circuit terminal
2 and earth. |
⇒ |
If greater than the specified range, test the low
reference circuit for an open/high resistance. If the circuit tests
normal, replace the K20 Engine Control Module. |
3. |
Ignition ON, verify the scan
tool ECT Sensor 1 parameter is colder than -39°C
(-38°F). |
⇒ |
If warmer than the specified range, test the
signal circuit terminal 2 for a short to ground. If the circuit
tests normal, replace the K20 Engine Control Module. |
|
Note: If the fuse in
the jumper wire opens, the signal circuit is shorted to a voltage
and the sensor may be damaged.
|
4. |
Install a 3 A fused jumper
wire between the signal circuit terminal 2 and the low reference
circuit terminal 1. Verify the scan tool ECT Sensor 1 parameter is
greater than 149°C (300°F). |
⇒ |
If less than the specified range, test the signal
circuit for a short to voltage or an open/high resistance. If the
circuit tests normal, replace the K20 Engine Control Module. |
5. |
If all circuits test normal,
test or replace the B34 Engine Coolant Temperature Sensor.
|
Component Testing
Static Test
1. |
Ignition off, disconnect the
harness connector at the B34 Engine Coolant Temperature
Sensor. |
|
Note: A thermometer
can be used to test the sensor off vehicle.
|
2. |
Test the B34 Engine Coolant
Temperature Sensor by varying the sensor temperature while
monitoring the sensor resistance. Compare the readings with the
Temperature Versus Resistance table and verify that the
resistance is within 5% of the specification. |
⇒ |
If not within the specified range, replace the B34
Engine Coolant Temperature Sensor. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|