P0128

FA20 ENGINE CONTROL: SFI SYSTEM: P0128; Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature); 2013 MY FR-S [03/2012 -]
P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

DESCRIPTION

At the same time as using the engine coolant temperature sensor to determine the engine coolant temperature, the ECM estimates the engine coolant temperature. If the difference between the estimated and actual engine coolant temperatures exceeds a predetermined value, then the DTC is stored, notifying of a malfunction in the functioning of the thermostat.





MONITOR DESCRIPTION

The ECM estimates the engine coolant temperature based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual engine coolant temperature. If the difference between the estimated engine coolant temperature and the actual engine coolant temperature exceeds the specified value, the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores the DTC.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

All





Case 1





Case 2





Case 3





TYPICAL MALFUNCTION THRESHOLDS

Case 1





Case 2





Case 3





CONFIRMATION DRIVING PATTERN





1. Connect the Techstream to the DLC3.

2. Turn the ignition switch to ON and turn the Techstream on.

3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation) Reading and Clearing Diagnostic Trouble Codes.

4. Turn the ignition switch off and wait for at least 30 seconds.

5. Turn the ignition switch to ON and turn the Techstream on.

6. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

7. Perform the following the confirmation driving pattern.

CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.

a. Drive the vehicle at 80 km/h (50 mph) or more for 20 minutes or more [A].

b. Stop the vehicle.

c. Idle the engine for 1 minute or more [B].

8. Enter the following menus: Powertrain / Engine / Trouble Codes.

9. Read pending DTCs.

HINT
* If a pending DTC is output, the system is malfunctioning.
* If a pending DTC is not output, perform the following procedure.

10. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

11. Input the DTC: P0128.

12. Check the DTC judgment result.





HINT
* If the judgment result shows NORMAL, the system is normal.
* If the judgment result shows ABNORMAL, the system has a malfunction.

13. If the test result is INCOMPLETE or N/A and no DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
* If a permanent DTC is output, the system is malfunctioning.
* If no permanent DTC is output, the system is normal.

INSPECTION PROCEDURE

HINT
* Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.
* When the DTC is output, check the engine coolant temperature using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Coolant Temp. If the Coolant Temp value is lower than the actual engine coolant temperature, the engine coolant temperature sensor circuit may be malfunctioning. In this case, check the wire harnesses and connectors (and those connections) between the ECM and the engine coolant temperature sensor first.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read DTCs.

Result





HINT
If any DTCs other than P0128 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. CHECK COOLING SYSTEM

(a) Check for defects in the cooling system that might cause the system to be too cold, such as abnormal cooling fan operation or any modifications.

NG -- REPAIR OR REPLACE COOLING SYSTEM
OK -- Continue to next step.

3. INSPECT THERMOSTAT

(a) Inspect the thermostat (thermostat opening temperature) Testing and Inspection.

NG -- REPLACE THERMOSTAT Removal

OK -- REPLACE ECM Removal