Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Insufficient Coolant Temperature for Closed Loop Fuel Control (P012500)
DESCRIPTION
Refer to DTC P011511.
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| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Memory | Note |
|---|---|---|---|---|---|---|
| P012500 | Insufficient Coolant Temperature for Closed Loop Fuel Control | The engine coolant temperature does not reach the closed loop enabling temperature for 20 minutes (this period varies with the engine coolant temperature at engine start) (2 trip detection logic). |
| Comes on | DTC stored | SAE Code: P0125 |
MONITOR DESCRIPTION
The resistance of the engine coolant temperature sensor varies in proportion to the actual engine coolant temperature. The ECM supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor. The signal output voltage varies according to the changing resistance of the sensor. After the engine is started, the engine coolant temperature is monitored by this signal. If the engine coolant temperature sensor indicates that the engine is not yet warm enough for closed loop fuel control, despite a specified period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the sensor or engine cooling system and stores the DTC.
MONITOR STRATEGY
| Related DTCs | P0125: Insufficient engine coolant temperature for closed loop fuel control |
| Required Sensors/Components (Main) | Engine coolant temperature sensor Water inlet with thermostat sub-assembly Engine cooling system |
| Required Sensors/Components (Related) | - |
| Frequency of Operation | Once per driving cycle |
| Duration | 69 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C [46.994°F]) or higher 157 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [66.992°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [46.994°F]) 1200 seconds: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [66.992°F]) |
| MIL Operation | 2 driving cycles |
| Sequence of Operation | None |
TYPICAL ENABLING CONDITIONS
| Monitor runs whenever the following DTCs are not stored | None |
| All of the following conditions are met | - |
| Thermostat fail (P0128) | Not detected |
| Intake air temperature sensor circuit fail (P0112, P0113) | Not detected |
| Engine coolant temperature sensor circuit fail (P0117, P0118) | Not detected |
| Mass air flow meter circuit fail (P0102, P0103) | Not detected |
TYPICAL MALFUNCTION THRESHOLDS
| Time until actual engine coolant temperature reaches closed loop fuel control enabling temperature | 69 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C [46.994°F]) or higher 157 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [66.992°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [46.994°F]) 1200 seconds: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [66.992°F]) |
CONFIRMATION DRIVING PATTERN
HINT:
-
After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
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-
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
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- Leave the vehicle outside overnight.
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG).
- Turn the Techstream on.
- Enter the following menus: Powertrain / Engine / Trouble Codes.
- Read the DTC and record the Freeze Frame Data.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
- Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature.
- Check that Coolant Temperature is the same or less than Initial Engine Coolant Temperature in the freeze frame data.
- Turn the engine switch off and wait for at least 30 seconds.
- Start the engine [A].
- Turn the Techstream on.
- Wait 21 minutes or more [B].
- Enter the following menus: Powertrain / Engine / Trouble Codes [C]..
-
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.
- Input the DTC: P012500.
-
Check the DTC judgment result.
Techstream Display
Description
NORMAL
- DTC judgment completed
- System normal
ABNORMAL
- DTC judgment completed
- System abnormal
INCOMPLETE
- DTC judgment not completed
- Perform driving pattern after confirming DTC enabling conditions
HINT:
- If the judgment result is NORMAL, the system is normal.
- If the judgment result is ABNORMAL, the system is malfunctioning.
-
If the judgment result is INCOMPLETE, let the engine cool down (engine coolant temperature is below 5°C (41°F)), and then perform steps [A] and [C]: Normal judgment procedure.
The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
- When clearing the permanent DTCs, do not disconnect the cable from the battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.
WIRING DIAGRAM
Refer to DTC P011511.
Click here
CAUTION / NOTICE / HINT
HINT:
- If any of DTCs P011511 or P011515 are output simultaneously with DTC P012500, the engine coolant temperature sensor may have an open or a short circuit. Troubleshoot those DTCs first.
- 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.
PROCEDURE
| 1. | CHECK ANY OTHER DTCS OUTPUT (IN ADDITION DTC P012500) |
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine / Trouble Codes.
(e) Read the DTCs.
Powertrain > Engine > Trouble Codes| Result | Proceed to |
|---|---|
| DTC P012500 is output | A |
| DTC P012500 and other DTCs are output | B |
HINT:
If any DTCs other than P012500 are output, troubleshoot those DTCs first.
| B |  | GO TO DTC CHART |
|
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| 2. | INSPECT WATER INLET WITH THERMOSTAT SUB-ASSEMBLY |
(a) Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).
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| NG | | REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY |
|
| 3. | CHECK ENGINE COOLING SYSTEM |
(a) Check for defects in the engine cooling system that might cause the system to be too cold, such as abnormal cooling fan operation or any modifications.
HINT:
Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.
Click here
| OK | | REPLACE ENGINE COOLANT TEMPERATURE SENSOR |
| NG | | REPAIR OR REPLACE ENGINE COOLING SYSTEM |
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual
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