Code No. P0183: Fuel Temperature Sensor Circuit High Input

OPERATION

A power voltage of 5 V is applied to the fuel temperature sensor output terminal from the engine-ECU connector terminal FTS.
The power voltage is earthed to the engine-ECU connector terminal FTSE from the fuel temperature sensor connector terminal.

FUNCTION

The fuel temperature sensor converts the intake air temperature into a voltage and inputs the voltage signal to the engine-ECU.
In response to the signal, the engine-ECU corrects the fuel injection amount, etc.
The fuel temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the intake air temperature rises. Therefore, the sensor output voltage varies with the fuel temperature, and becomes lower as the fuel temperature rises.

TROUBLE JUDGMENT

Check Conditions

Battery positive voltage is 8 - 16 V
2 seconds later after the ignition switch has been in "ON" position or the engine has started up.

Judgment Criterion

The fuel temperature sensor output voltage is 4.95 V or more.

FAIL-SAFE AND BACKUP FUNCTION

The fuel temperature is controlled to be 45°C (Start-up of -25°C)
The AS&G control is prohibited.

PROBABLE CAUSES

Failed fuel temperature sensor
Open circuit or harness damage in fuel temperature sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III data list

Item 21: Fuel temperature sensor

OK: At ambient temperature (fuel temperature) or equivalent.

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Go to Step 2.

STEP 2. Check fuel temperature sensor itself.

Fuel temperature sensor connector check.
Check fuel temperature sensor itself (Refer to ).

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or replace the fuel temperature sensor.

STEP 3. Perform voltage measurement at fuel temperature sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal engine-ECU FTS line and body earth.

OK: 4.5 - 4.9 V

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 4.

STEP 4. Check harness between fuel temperature sensor connector terminal and engine-ECU connector terminal FTS.

Check output line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 5. M.U.T.-III data list

Item 21: Fuel temperature sensor

OK: At ambient temperature (fuel temperature) or equivalent.

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Replace the engine-ECU.

STEP 6. Perform resistance measurement at fuel temperature sensor connector.

Disconnect connector, and measure at harness side.
Resistance between terminal engine-ECU FTSE line and body earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 5.

	Go to Step 7.

STEP 7. Check harness between fuel temperature sensor connector terminal and engine-ECU connector terminal FTSE.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.