P1544
DTC P1544: DOR Tampering Monitor (Temperature Check Before Thermostat Open)Radiator Sensor Circuit Part 1:
Radiator Sensor Circuit Part 2:
RADIATOR SENSOR CIRCUIT
CIRCUIT OPERATION
- The battery voltage is applied from the MFI relay to the radiator sensor (terminal No. 3), and it is grounded to the vehicle body from the radiator sensor (terminal No. 1).
- The radiator sensor (terminal No. 2) sends the sensor signal to the ECM (terminal No. 99).
MONITOR EXECUTION
- Once per driving cycle
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Not applicable
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Condition
- Battery positive voltage is higher than 11 volts.
- Intake air temperature is between 0 °C (32 °F) to 40 °C (104 °F) when the engine is started.
- Engine coolant temperature is between 0 °C (32 °F) to 40 °C (104 °F) when the engine is started.
- The engine coolant temperature - intake air temperature is 5 °C (41 °F) or less when the engine is started.
- Vehicle speed is lower than 1.5 km/h (1 mph).
Judgement Criteria
- When the output temperature of the radiator sensor before the thermostat valve is opened is high, the sensor is defective.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 19. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Tampering of the DOR radiator
- Thermostat failed.
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
STEP 1. Check the thermostat.
Thermostat inspection (Refer to Thermostat inspection).
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair it. Then go to Step 4.
STEP 2. DOR radiator sensor installation check.
Check that the sensor is installed securely and operates normally.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Replace the DOR radiator. Then go to Step 4.
STEP 3. Replace the DOR radiator.
1. Replace the DOR radiator.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
2. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.
4. Read the DTC.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC P1544 set?
YES: Replace the ECM. When the ECM is replaced, register the ID code. ID Code Registration Judgment Table
NO: It can be assumed that this malfunction is intermittent.
STEP 4. Perform the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 19. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P1544 set?
YES: Repeat the troubleshooting.