Forced Limited Power Excessive High Coolant Temp

(P0128) FORCED LIMITED POWER EXCESSIVE HIGH COOLANT TEMP





When Monitored and Set Condition
^ When Monitored: With the ignition on engine running.
^ Set Condition: The Engine Coolant Temperature (ECT) Sensor exceeds 130°C (265°F) at the PCM. One trip Fault

POSSIBLE CAUSES
- ENGINE COOLANT TEMPERATURE (ECT) SENSOR
- RADIATOR FAN CONTROL MODULE
- RADIATOR FAN
- LOW COOLANT LEVEL
- THERMOSTAT OPERATION
- POWERTRAIN CONTROL MODULE



Diagnostic Test
1. PRE-DIAGNOSTIC CHECK OUT





Note: Always perform diagnostics with a fully charged battery.

Note: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.

Note: Check for applicable TSBs related to the problem. Turn the ignition on. With the DRBIII, read PCM DTCs. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary. Perform this procedure prior to symptom diagnosis.

Continue
Go To 2

2. LOW COOLANT LEVEL





Note: If any ECT or Radiator Fan Control Module DTCs have set along with this DTC, diagnose them first before continuing.

Note: If a Engine Coolant Temperature (ECT) DTC is set along with this code, diagnose the ECT DTC first.

Note: Inspect the ECT terminals and related PCM terminals. Ensure the terminals are free from corrosion and damage.

Note: The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have a completely cold soaked engine.

WARNING: NEVER OPEN THE COOLING SYSTEM WHEN THE ENGINE IS HOT. THE SYSTEM IS UNDER PRESSURE. EXTREME BURNS OR SCALDING MAY RESULT. ALLOW THE ENGINE TO COOL BEFORE OPENING THE COOLING SYSTEM.

Check the coolant system to make sure that the coolant is in good condition and at the proper level.
Is the coolant level and condition OK?
Yes >> Go To 3
No >> Inspect the vehicle for a coolant leak and add the necessary amount of coolant. Perform POWERTRAIN VERIFICATION TEST VER - 2.

3. THERMOSTAT OPERATION





Note: This test works best if performed on a cold engine (cold soak).

Turn the ignition on.
With the DRBIII read the ENG COOLANT TEMP value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.

Note: If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F). is reached.

Start the Engine.
During engine warm-up, monitor the ENG COOLANT TEMP value. The temperature change should be a smooth transition from start up to normal operating temp 82°C (180°F). Also, monitor the actual coolant temperature with a thermometer.

Note: As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the ENG COOLANT TEMP value in the DRBIII should stay relatively close to each other.
Using the appropriate service information, determine the proper opening temperature of the thermostat.
Did the thermostat open at the proper temperature?
Yes >> Go To 4
No >> Replace the thermostat. Perform POWERTRAIN VERIFICATION TEST VER - 2.

4. PCM





Note: Inspect the ECT Sensor terminals and related PCM terminals. Ensure the terminals are free from corrosion and damage.

Note: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for a DTC. Turn the ignition on. With the DRBIII, erase PCM DTCs.

Note: It maybe necessary to road test the vehicle for this DTC to set. With the DRBIII, read PCM DTCs.

Did this DTC set again?
Yes >> Replace and program the Powertrain Control Module. Perform POWERTRAIN VERIFICATION TEST VER - 2.
No >> Go To 5

5. INTERMITTENT WIRING AND CONNECTORS
The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.

Note: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors specific to this DTC. Wiggle the wires while checking for shorts and open circuits.

Note: Check for any Technical Service Bulletins that may apply.

Were there any problems found?
Yes >> Repair as necessary. Perform POWERTRAIN VERIFICATION TEST - VER 2 Powertrain Verification Test - Ver 2.
No >> The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.