AMERICAN STANDARD ERROR CODES
Data Verified: January 2026
Professional diagnostic codes and troubleshooting steps.
Technical Note: AMERICAN STANDARD systems are part of a shared manufacturing platform. These codes are identical for TRANE.
Medium Severity
CL2.001.00
PS3 Open (3rd Stage Pressure Switch)
Troubleshooting Steps
- • Check for restricted vent piping or improper pipe sizing.
- • Inspect pressure switch tubing for moisture, kinks, or disconnection.
- • Verify flue gas condensate is not backing up in the secondary heat exchanger.
Source Reference Trane Service Manual
Medium Severity
CL2.001.01
PS3 Closed (3rd Stage Pressure Switch)
Troubleshooting Steps
- • Check for pressure switch contacts stuck closed.
- • Verify the draft inducer motor is not running without a call for heat.
- • Inspect wiring for a short circuit to the pressure switch.
Source Reference Trane Service Manual
Medium Severity
CL2.001.02
PS2 Open (2nd Stage Pressure Switch)
Troubleshooting Steps
- • Ensure the draft inducer motor is reaching the correct RPM for 2nd stage.
- • Check for blockages in the intake air pipe.
- • Inspect the heat exchanger for any significant soot buildup or restriction.
Source Reference Trane Service Manual
High Severity
CL2.001.04
PS1 Open (1st Stage Pressure Switch)
Troubleshooting Steps
- • Check for a completely blocked vent or failed inducer motor.
- • Verify the pressure switch diaphragm hasn't ruptured.
- • Ensure the condensate drain trap is primed and not overflowing.
Source Reference Trane Service Manual
High Severity
CD1.002.00
Ignition Failure / No Flame Detected
Troubleshooting Steps
- • Verify gas valve is turned on and gas pressure is sufficient.
- • Clean the flame sensor rod with a non-metallic abrasive pad.
- • Inspect the igniter for cracks or a failed 'glow' during the start sequence.
Source Reference Trane Service Manual
Medium Severity
CD1.003.00
Flame Lost After Ignition
Troubleshooting Steps
- • Check for unstable gas pressure or wind gusts entering the vent.
- • Inspect the burner assembly for proper alignment with the flame sensor.
- • Ensure the furnace is properly grounded.
Source Reference Trane Service Manual
High Severity
CD3.001.00
Limit Switch Open (Overheat)
Troubleshooting Steps
- • Immediately check for a very dirty air filter or failed blower motor.
- • Inspect all supply registers to ensure enough are open.
- • Verify the static pressure in the ductwork isn't exceeding 0.8" WC.
Source Reference Trane Service Manual
Critical Severity
SOP.004.56
Major Discharge Temp Sensor Trip
Troubleshooting Steps
- • The discharge temperature has exceeded safe limits. Check for low refrigerant charge.
- • Verify the discharge temperature thermistor is accurately sensing pipe temp.
- • Ensure the outdoor fan is moving enough air and the coil is not obstructed.
Source Reference Trane Service Manual
High Severity
ERR.001.01
Indoor Unit Communication Loss
Troubleshooting Steps
- • Check the data lines (D1/D2 or ABCD) for loose connections at the furnace/air handler.
- • Verify 24V power is present at the indoor control board.
- • Inspect for interference from high-voltage lines running parallel to communication wires.
Source Reference Trane Service Manual
Medium Severity
SOP.002.01
Evaporator Coil Freeze Protection Active
Troubleshooting Steps
- • Check for very low airflow caused by a clogged filter or collapsed duct.
- • Verify that the indoor blower is running at the correct speed for the cooling call.
- • Inspect the expansion valve (EEV/TXV) for proper refrigerant metering.
Source Reference Trane Service Manual
Medium Severity
SOP.007.02
Liquid Line Sensor Fault
Troubleshooting Steps
- • Check the liquid line thermistor for a short or open circuit.
- • Verify the sensor is tightly clipped to the refrigerant line and insulated.
- • Replace the sensor if resistance values do not match the manufacturer's temp chart.
Source Reference Trane Service Manual
Critical Severity
CD1.006.01
Flame Sensed When No Gas Valve Energized
Troubleshooting Steps
- • Check for a leaking gas valve that is staying partially open.
- • Inspect for a 'ghost flame' signal caused by a faulty ignition control board.
- • Verify there is no moisture on the flame sensor or control board circuitry.
Source Reference Trane Service Manual
Critical Severity
CD2.001.00
Gas Valve Relay Coil Fault
Troubleshooting Steps
- • Check for a failed relay on the furnace control board.
- • Verify 24V is reaching the gas valve during a call for heat.
- • Replace the control board if the internal relay is 'stuck' or unresponsive.
Source Reference Trane Service Manual
Medium Severity
CD4.002.01
Blower Motor Speed Out of Range
Troubleshooting Steps
- • Check for excessive static pressure in the ductwork.
- • Verify the blower wheel is not weighted down by dust or insulation.
- • Inspect the motor’s control module for signs of moisture or electrical damage.
Source Reference Trane Service Manual
Medium Severity
CD4.002.01
Blower Motor Speed Out of Range
Troubleshooting Steps
- • Check for excessive static pressure in the ductwork.
- • Verify the blower wheel is not weighted down by dust or insulation.
- • Inspect the motor’s control module for signs of moisture or electrical damage.
Source Reference Trane Service Manual
Medium Severity
SOP.007.01
Outdoor Coil Temperature Sensor Fault
Troubleshooting Steps
- • Check the thermistor resistance; compare it to the standard Trane 10k-ohm temp chart.
- • Verify the sensor is not making contact with the outdoor fan blade or chassis.
- • Inspect the wiring harness for signs of rodent damage or UV degradation.
Source Reference Trane Service Manual
High Severity
CD4.003.00
Blower Motor No Communication (Data Lost)
Troubleshooting Steps
- • Verify the 4-pin communication cable is securely seated on both the motor and control board.
- • Check for 24V power at the motor's low-voltage connector.
- • Replace the motor's electronic control module (ECM) if power is present but data is not.
Source Reference Trane Service Manual
Critical Severity
CFG.001.02
Multiple Indoor Unit Configuration Fault
Troubleshooting Steps
- • The system detected more than one communicating indoor unit on the bus (not supported).
- • Perform a 'Restore Factory Defaults' via the thermostat to re-discover equipment.
- • Disconnect any unauthorized accessories sharing the communication bus.
Source Reference Trane Alert Codes
Normal Severity
CL2.033.00
Polarity Error (Line Voltage Reversed)
Troubleshooting Steps
- • Check if the Hot and Neutral wires are swapped at the furnace junction box.
- • Verify the furnace has a solid copper ground wire to the chassis.
- • Measure voltage between Neutral and Ground; it should be less than 10V AC.
Source Reference Trane Alert Codes