DTC B3933
Diagnostic Instructions
DTC Descriptors
| DTC B3933 02: Air Conditioning Evaporator
Temperature Sensor Circuit Short to Ground |
| DTC B3933 05: Air Conditioning Evaporator
Temperature Sensor Circuit High Voltage/Open |
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
Evaporator Temperature Sensor Signal
|
B3933 02
|
B3933 05
|
B3933 05
|
1
|
Evaporator Temperature Sensor Low Reference
|
-
|
B3933 05
|
B3933 05
|
-
|
1. Air Temperature Malfunction
|
|
| |
Circuit/System Description
The A/C evaporator temperature sensor is a 2-wire negative
temperature co-efficient thermistor. A signal and low reference
circuit enables the sensor to operate. As the air temperature
surrounding the sensor increases, the sensor resistance decreases.
The sensor signal voltage decreases as the resistance decreases.
The sensor operates within a temperature range between -40 to
+85°C (-40 to +185°F). The sensor signal varies between 0-5
V. The HVAC control module converts the signal to a range between
0-255 counts. As the air temperature increases the count value will
decrease. If the HVAC control module detects a malfunctioning
sensor, then the control module software will use a default air
temperature value. The default action ensures that the HVAC system
can adjust the inside air temperature near the desired temperature
until the condition is corrected.
Conditions for Running the DTC
| • |
The HVAC control module is
ON. |
Conditions for Setting the DTC
The HVAC control module detects the sensor signal out of range.
The signal voltage is less than 0.1 V or greater than 4.9 V for
more than 50 ms.
Action Taken When the DTC Sets
The system operates using a default value.
Conditions for Clearing the DTC
The sensor signal is within specified range between 0.1-4.9
V.
Reference Information
Schematic Reference
HVAC Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Manual HVAC Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
| 1. |
Verify that no DTC is
set. |
⇒ If a DTC is
set
Refer to Circuit/System Testing.
⇓ If no DTC is
set
| 2. |
Measure actual evaporator
temperature using a thermometer. Compare this value to the scan
tool A/C Evaporator Temperature Sensor parameter. The measured
temperature should be within 5°C (9°F) difference of
parameter value. |
⇒ If not within the
specified range
Replace the B39 A/C Evaporator
Temperature Sensor. ⇓
If within the specified range
Circuit/System Testing
| 1. |
Ignition OFF, remove the
ignition key, open the driver door, disconnect the scan tool and
disconnect the harness connector at the B39 A/C Evaporator
Temperature Sensor. |
|
Note: Some control
module ground circuits may require up to 20 min to achieve a
resistance reading of less than 10 Ω. In most cases the
readings will drop below 20 Ω within 1 min indicating the
control modules are going to sleep.
|
| 2. |
Test for less than 10 Ω
between the B39 A/C Evaporator Temperature Sensor low reference
circuit terminal 2 and ground. |
⇒ If greater than 10
Ω
Repair the open/high resistance in
the circuit. ⇓ If
less than 10 Ω
| 3. |
Ignition ON, test for 4.8-5.2
V between the B39 A/C Evaporator Temperature Sensor signal circuit
terminal 1 and ground. |
⇒ If less than 4.8
V
| |
3.1 |
Ignition OFF, disconnect the
X3 harness connector at the K33 HVAC Control Module. |
| |
3.2 |
Test for infinite resistance
between the signal circuit and ground. |
| ⇒ |
If less than infinite resistance, repair the short to ground on
the circuit. |
| |
3.3 |
Test for less than 2 Ω
in the signal circuit end to end. |
| ⇒ |
If 2 Ω or greater, repair the open/high resistance in the
circuit. |
| ⇒ |
If less than 2 Ω, replace the K33 HVAC Control
Module. |
⇒ If greater than
5.2 V
| |
3.1 |
Ignition OFF, disconnect the
X3 harness connector at the K33 HVAC Control Module. |
| |
3.2 |
Ignition ON, test for less
than 0.3 V between the signal circuit and ground. |
| ⇒ |
If greater than 0.3 V, repair the short to voltage on the
circuit. |
| ⇒ |
If less than 0.3 V, replace the K33 HVAC Control Module. |
⇓ If within 4.8-5.2
V
| 4. |
Replace the B39 A/C Evaporator
Temperature Sensor and verify the DTC does not reset. |
⇒ If DTC
resets
Replace the K33 HVAC Control Module.
⇓ If DTC does not
reset
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|
