B1203

DTC B1203 WATER TEMPERATURE SENSOR SHORT (LOW)

Component Location:

GENERAL DESCRIPTION
The Water Temp. Sensor located at heater unit, detects coolant temperature. Its signal is used for cold engine lockout control. When the driver operates the heater before the engine is warmed up, the signal from sensor causes the heater control unit to reduce blower motor speed until coolant temperature reaches the threshold value.

DTC DESCRIPTION
The A/C controller sets DTC B1203 if there is a short circuit in Water Temp. Sensor signal harness or the measured resistance value of sensor is less than threshold value(about 1.2 Kohms)

DTC Detecting Condition:

Specification:

MONITOR SCANTOOL DATA
1. Connect scan tool to data link connector(DLC).
2. Engine "ON"




3. Monitor the "Water Temp. Sensor" Parameter on the Scantool.
4. Is the DTC B1203 present and is parameter of "Water Temp. Sensor" fixed?
Parameter of "Water Temp. Sensor" will be fixed at -2 degrees C (28.4 degrees F), if there is any fault in Water Temp. Sensor.

YES: Go to "Inspection" procedure.

NO: The electrical systems are made up of many harness and connectors. Many kinds of fault are caused by poor connection of sensors and terminals. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.

TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminals.
Faults can also be caused by interference from other electrical Systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3. Has a problem been found?

YES: Repair as necessary and go to "Verification of Vehicle Repair" procedure.

NO: Go to "Signal Circuit Inspection" procedure.

SIGNAL CIRCUIT INSPECTION
1. Check for short to ground in harness.
1. Ignition "OFF"
2. Disconnect Water Temp. Sensor.




3. Measure resistance between terminal "1" of Water Temp. Sensor and chassis ground.

Specification: Approx. infinite Ohm

4. Is the measured resistance within specifications?

YES: Go to "Component Inspection" procedure.

NO: Check for short to ground in harness. Repair as necessary and go to "Verification of Vehicle Repair" procedure.

COMPONENT INSPECTION
1. Check Water Temp. Sensor.
1. Ignition "OFF"
2. Disconnect Water Temp. Sensor.




3. Measure resistance between terminal "1" and "2" of Water Temp. Sensor.

Specification: Refer the specifications in fig 3.

4. Is the measured resistance within specifications in fig 3)? (tolerance limits ± 3%)

YES: Go to "Check Heater & A/C controller" procedure.

NO: Substitute with a known-good Water Temp. Sensor and check for proper operation.
If the problem is corrected, replace Water Temp Sensor and then go to "Verification of Vehicle Repair" procedure.

2. Check Heater & A/C controller
1. Engine "ON"
2. Disconnect Water Temp. Sensor.




3. Measure Voltage between terminal "7" of Heater & A/C controller and chassis ground.

Specification: Approx. 5 V

4. Is the measured voltage within specifications?

YES: Check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.

NO: Substitute with a known-good Heater & A/C controller and check for proper operation.
If the problem is corrected, replace Heater & A/C controller and then go to "Verification of Vehicle Repair" procedure.

VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Connect Scantool and select "Diagnostic Trouble Codes(DTCs)" mode and then clear DTC.
2. Operate the vehicle and monitor the DTC on the Scantool.
3. Are any DTCs present?

YES: Go to the applicable troubleshooting procedure.

NO: System is performing to specification at this time.