P1540

DTC P1540: LIN Communication Check by PCM (Sending Message to Radiator Sensor)/DTC P1541: LIN Communication Check by PCM (Receiving Message from Radiator Sensor)

Radiator Sensor Circuit (Part 1):

Radiator Sensor Circuit (Part 2):

CIRCUIT OPERATION
- The battery voltage is applied from the ignition switch 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 powertrain control module (terminal No.3).

TECHNICAL DESCRIPTION
- The PCM judges the tampering of the DOR radiator according to the signal from the radiator sensor.

MONITOR EXECUTION
- Continuous

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:

Check Condition
- Ignition switch: "ON"
- Battery positive voltage is higher than 10 volts
- Engine coolant temp -30 °C (-22 °F) to 105 °C (221 °F)

Judgement Criteria
- The radiator sensor cannot receive the data from the PCM [When P1540 is set].
- The PCM cannot receive the data from the radiator sensor [When P1541 is set].
- When the PCM is defective

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Tampering of the DOR radiator
- Malfunction of the PCM
- A poor connection, open circuit, short circuit or damaged circuit is present in the radiator sensor circuit.

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. Measure the battery positive voltage.

1. Measure the battery positive voltage during cranking.
- The voltage should remain greater than 8 volts while the engine is cranked.

Q: Does the voltage remain greater than 8 volts while the engine is cranked?

YES : Go to Step 2.

NO : Refer to Battery check. Battery Check

STEP 2. Check harness connector A-41 at the radiator sensor for damage.






Q: Is the harness connector in good condition?

YES : Go to Step 3.

NO : Repair or replace it. Then go to Step 9.

STEP 3. Measure the supply voltage at radiator sensor connector A-41.




1. Disconnect radiator sensor harness connector A-41.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between harness connector A-41 terminal No.3 and ground.
- The voltage should equal battery positive voltage.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the measured voltage battery positive voltage?

YES : Go to Step 6.

NO : Go to Step 4.

STEP 4. Check intermediate connector A-13 for loose, corroded or damaged terminals, or terminals pushed back in the connector.






Q: Are the connectors and terminals in good condition?

YES : Go to Step 5.

NO : Repair or replace the damaged components. Then go to Step 9.

STEP 5. Check for harness damage between radiator sensor connector A-41 (terminal No.3) and MFI relay connector B-17X (terminal No.4).






Q: Is the harness wire in good condition?

YES : Then go to Step 6.

NO : Repair it. Then go to Step 9.

STEP 6. Check for continuity at radiator sensor harness side connector A-41




1. Disconnect the connector A-41 and measure at the harness side.
2. Check for the continuity between terminal No.1 and ground.
- Should be less than 2 ohms.

Q: Does continuity exist?

YES : Go to Step 7.

NO : Repair it. Then go to Step 9.

STEP 7. Check for harness damage between radiator sensor connector A-41 (terminal No.1) and PCM connector B-19 (terminal No.3).




- Check the communication lines for earth circuit. [When P1540 is set]
- Check the communication lines for open circuit. [When P1541 is set]

Q: Is the harness wire in good condition?

YES : Go to Step 8.

NO : Repair it. Then go to Step 9.

STEP 8. Replace the DOR radiator Check the diagnostic trouble code (DTC).

Q: Is DTC P1540 or P1541 set?

YES : Replace the PCM. Then go to Step 9.

NO : The procedure is complete.

STEP 9. Perform the OBD-II drive cycle.

Check the diagnostic trouble code (DTC).

Q: Is DTC P1540 or P1541 set?

YES : Repeat the troubleshooting.

NO : The procedure is complete.