B1030-11

B1030-11-EVAPORATOR TEMPERATURE SENSOR - CIRCUIT SHORT TO GROUND







Theory of Operation

The Evaporator Temperature Sensor is a variable resistor that changes in conjunction with temperature, or otherwise known as a thermistor. The Evaporator Temperature Sensor is located in the HVAC housing downstream of the A/C evaporator. The A/C Heater Control module monitors the evaporator temperature by monitoring the voltage change of the Evaporator Temperature Sensor Signal circuit. The sensor thermistor forms the lower half of a voltage divider and the upper half of the voltage divider is provided by a pull up resistor to 5.0 volts. If the monitored voltage drops below or rises above a predetermined voltage, a DTC will set.

- When Monitored:
With the ignition on.

- Set Condition:
The Evaporator Temperature Sensor voltage input to the A/C Heater Control is below a calibrated range for a continuous period of 30 seconds. If the A/C Heater Control detects a valid voltage, the DTC will change from active to stored and will stay stored for 100 ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT VOLTAGE
1. Ignition on, engine not running.
2. With the scan tool, read HVAC DTCs.

NOTE: It can take up to 30 seconds or more for this DTC to mature.

Is this DTC active?

Yes

- Go To 2

No

- Go To 5

2. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off.
2. Disconnect the A/C Heater Control C1 harness connector.
3. Disconnect the Evaporator Temperature Sensor harness connector.
4. Measure the resistance between ground and the (C21) Evaporator Temperature Sensor Signal circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C21) Evaporator Temperature Sensor Signal circuit for a short to ground.
- Perform HVAC VERIFICATION TEST HVAC Verification Test.

No

- Go To 3

3. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO (C121) SENSOR GROUND CIRCUIT




1. Measure the resistance between the (C21) Evaporator Temperature Sensor Signal circuit and the (C121) Sensor Ground circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C21) Evaporator Temperature Sensor Signal circuit for a short to (C121) Sensor Ground circuit.
- Perform HVAC VERIFICATION TEST HVAC Verification Test.

No

- Go To 4

4. CHECK THE EVAPORATOR TEMPERATURE SENSOR
1. Replace the Evaporator Temperature Sensor.
2. Perform HVAC VERIFICATION TEST HVAC Verification Test.

Does the DTC reset?

Yes

- Replace the A/C Heater Control.
- Perform HVAC VERIFICATION TEST HVAC Verification Test.

No

- Test complete.

5. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
4. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, or partially broken wires.
5. Check the connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals.
6. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform HVAC VERIFICATION TEST HVAC Verification Test.

No

- Test complete.