P0181
Fuel Temperature Sensor Circuit:
Connectors:
CIRCUIT OPERATION
- 5-volt voltage is applied to the fuel temperature sensor output terminal (terminal No.3) from the ECM (terminal No.96)
- The fuel temperature sensor output voltage increases when the resistance increases and decreases when the resistance decreases. The ground terminal (terminal No.1) is grounded to the vehicle body.
TECHNICAL DESCRIPTION
- The fuel temperature sensor converts the fuel temperature to a voltage.
- The ECM
DTC SET CONDITIONS
Check Conditions
- The engine coolant temperature intake air temperature is 5 °C (9 °F) or less when the engine is started.
- The engine coolant temperature is between - 100 °C (14 °F) and 36 °C (97 °F) when the engine is started.
- Engine coolant temperature is higher than 60 °C (140 °F).
- Maximum vehicle speed is higher than 30 km/h (17 mph) after the starting sequence has been completed.
Judgement Criteria
- The fuel temperature - engine coolant temperature is 15 °C (27 °F) or more when the engine is started.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Fuel temperature sensor failed.
- Open or shorted fuel temperature sensor circuit, or loose connector.
- ECM failed.
- PCM failed.
NOTE: A diagnostic trouble code (DTC) could be output if the engine coolant is changed as indicated below Because this is not a failure, the DTC must be erased.
Make sure to test drive the vehicle in accordance with the drive cycle pattern in order to verify that a DTC will not be output.
The engine and the radiator have been flushed repeatedly when the engine coolant temperature was high (or the fuel temperature was high).
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Using scan tool MB991502, check data list item 4A: Fuel Temperature Sensor.
CAUTION
To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991502 to the data reading mode for item 4A, Fuel Temperature Sensor.
- With the engine cool, the fuel temperature should be approximately the same as ambient air temperature.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to INTRODUCTION, How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Check connector D-17 at the fuel temperature sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 3.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
STEP 3. Check the fuel temperature sensor.
1. Disconnect the fuel temperature sensor connector D-17.
2. Measure the resistance between terminal No.1 and No.3 of the fuel temperature sensor.
Standard value: 0.5 - 12.0 kohms
Q: Is the resistance between 0.5 and 12.0 kohms?
YES: Go to Step 4.
NO: Replace the fuel temperature sensor. Then go to Step 12.
STEP 4. Check the continuity at fuel temperature sensor harness side connector D-17.
1. Disconnect the connector D-17 and measure at the harness side.
2. Check for the continuity between terminal No.1 and ground.
- Should be less than 2 ohms.
Q: Is the continuity normal?
YES: Go to Step 5.
NO: Repair harness wire between fuel temperature sensor connector D-17 (terminal No.1) and ground because of open circuit or harness damage. Then go to Step 12.
STEP 5. Measure the sensor supply voltage at fuel temperature sensor harness side connector D-17.
1. Disconnect the connector D-17 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.3 and ground.
- Voltage should be between 4.5 and 4.9 volts
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.5 and 4.9 volts?
YES: Go to Step 6.
NO: Go to Step 10.
Connectors:
STEP 6. Measure the sensor supply voltage at ECM connector C-i22
1. Do not disconnect the ECM connector C-122
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.96
- When fuel temperature is 0 °C (32 °F), voltage should be 2.7 and 3.1 volts.
- When fuel temperature is 20 °C (68 °F), voltage should be 2.1 and 2.5 volts.
- When fuel temperature is 40 °C (104 °F), voltage should be 1.6 and 2.0 volts.
- When fuel temperature is 80 °C (176 °F), voltage should be 0.8 and 1.2 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 7.
NO: Go to Step 8.
Connectors:
STEP 7. Check connector C-122 at ECM
Q: Is the connector in good condition?
YES: Check connector C-25 and C-210 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector are in good condition, repair harness wire between fuel gauge unit connector D-17 (terminal No.3) and ECM connector C-122 (terminal No.96)
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
Connectors:
STEP 8. Check connector C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
Connectors:
STEP 9. Check for short circuit to ground between fuel gauge unit connector D-17 (terminal No.3) and ECM connector C-122 (terminal No.96)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 12.
NO: Repair it. Then go to Step 12.
Connectors:
STEP 10. Check connector C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 11.
NO: Repair or replace it. Refer to Harness Connector inspection. Then go to Step 12.
Connectors:
STEP 11. Check for harness damage between fuel temperature sensor connector D-17 (terminal No.3) and ECM connector C-122 (terminal No.96)
NOTE: Check harness after checking intermediate connector D-25 and C-210. If intermediate connector are damaged, repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 12.
NO: Repair it. Then go to Step 12.
STEP 12. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0181 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.