DTC P0128 - LDE or LLU
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
- Ignition OFF, inspect the cooling system surge tank
for the proper coolant level. Refer to
Loss of Coolant and
Cooling System Draining and Filling .
- 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.
- 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
equalise.
- 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. |
- 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).
- Engine idling, observe the DTC information with a scan
tool. DTC P0128 00 should not set.
- 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
- Ignition OFF, disconnect the harness connector at the
B34 Engine Coolant Temperature Sensor.
- Ignition OFF for 1 min, test for less than
5 Ω between the low reference circuit terminal 2 and
ground.
⇒ |
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. |
- 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.
- Install a 3A 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. |
- If all circuits test normal, test or replace the
B34 Engine Coolant Temperature Sensor.
Component Testing
Static Test
- Ignition off, disconnect the harness connector at the
B34 Engine Coolant Temperature Sensor.
Note: A thermometer can be used
to test the sensor off the vehicle.
- 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.
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