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Circuit/System Testing
1. Ignition OFF, disconnect the air temperature actuator harness connector at the air temperature actuator.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal 1and ground.
➢ If greater than 1.0 ohm, test the low reference circuit for an open/high resistance. If the circuit tests normal,
replace the hvac control module.
3. Ignition ON, test for 4.8 to 5.2 volts between the 5 -volt reference circuit terminal 3 and ground.
➢ If less than 4.8 volts, test the 5 -volt reference circuit for a short to ground or an open/high resistance. If the circuit
tests normal, replace the hvac control module.
➢ If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace
the HVAC control module.
4. Install a 3-amp fused jumper wire at the signal circuit terminal 2, test for greater than 5 volts. Toggle the jumper
wire between the low reference circuit terminal and the 5-volt reference circuit terminal.
➢ If the position signal parameter is less than 5 volts, test the signal circuit for a short to voltage, or an open/high
resistance. If the circuit tests normal, replace the HVAC control module.
5. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit A terminal 4 and B+.
6. Ignition OFF, verify that a test lamp does not illuminate between control circuit terminal A terminal 4 and B+.
➢ If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal replace the
HVAC control module.
7. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit B terminal 5 and B+.
➢ If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the
circuit tests normal, replace the HVAC control module.
8. Ignition OFF, verify that the test lamp does not illuminate between control circuit B terminal 5 and B+.
➢ If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal replace the
HVAC control module.
9. If all circuits test normal, replace the air temperature actuator.
Repair Instructions
Perform the "Diagnostic Repair Verification - Vehicle Diagnostic Information: " after completing the diagnostic
procedure.
• "Control Module References: "
• "Air Temperature Actuator Replacement"
Too Cold in Vehicle
Diagnostic Instructions
• Perform the "Diagnostic System Check - Vehicle Diagnostic Information: " prior to using this diagnostic procedure.
• "Strategy Based Diagnosis: "
• "Diagnostic Procedure Instructions - Vehicle Diagnostic Information: "
Diagnostic Fault Information
Circuit
Air Temperature Door Control A Circuit
Air Temperature Door Control B Circuit
5-Volt Reference
Air Temperature Door Position Signal
Air Temperature Actuator Low Reference
B+ circuit of the HVAC control module
Ground circuit of the HVAC control module
*-Air Temperature Circuit Inoperative
Heating, Ventilation and Air Conditioning:
Short to
Open/High
Ground
Resistance
*
*
*
*
*
*
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*
—
*
*
*
—
*
Short to
Signal
Voltage
Performance
*
—
*
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*
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*
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7A-53
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Table of Contents
Troubleshooting
