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Tahoe / Yukon Service Manual

DTC P0535, P0537, P0538, or P153B (L84, L87)

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptors DTC P0535 Air Conditioning Evaporator Temperature Sensor Circuit DTC P0537 Air Conditioning Evaporator Temperature Sensor Circuit Low DTC P0538 Air Conditioning Evaporator Temperature Sensor Circuit High DTC P153B Air Conditioning Evaporator Temperature Sensor Not Plausible For symptom byte information refer to Symptom Byte List. Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performance
6137 Signal P0537 P0538 P0538 P0535
407 Low Reference — P0538 P0538 —

Circuit/System Description The B39 Air Conditioning Evaporator Air Temperature Sensor is a 2-wire negative temperature coefficient thermistor. The sensor operates using signal and low reference circuits. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor sends a signal voltage between 0–5 V. If the BCM detects a malfunctioning sensor the software uses 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 P0535 The BCM is awake and communicating System voltage = 9 – 16 V DTCs P0537 or P0538 are not set P0537, P0538 The BCM is awake and communicating System voltage = 9 – 16 V P153B Vehicle OFF for approximately 8 hours The BCM is awake and communicating System voltage = 9 – 16 V DTCs P0535, P0537 or P0538 are not set Conditions for Setting the DTC P0535 The rate of change of the evaporator air temperature signal voltage has exceeded a calibrated value P0537 The evaporator air temperature signal voltage is too low out of the expected range. P0538 The evaporator air temperature signal voltage is too high out of the expected range. P153B The absolute difference between the value of the Evaporator Air Temperature and Outside Air Temperature sensors exceeds the calibrated value. or The absolute difference between the value of the Evaporator Air Temperature and Inlet Air Temperature sensors exceeds the calibrated value. Action Taken When the DTC Sets The system operates using a default value. DTC Type C Conditions for Clearing the DTC The evaporator air temperature signal is within specified range DTC Type C Diagnostic Aids DTC P153B may be caused by an inaccurate value from either the Outside Air Temperature or Intake Air Temperature sensors. Reference Information Schematic Reference HVAC Schematics Connector End View Reference Master Electrical Component List Description and Operation Automatic HVAC Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Testing

  1. Ignition/Vehicle OFF, disconnect the harness connector at the B39 Air Conditioning Evaporator Air Temperature Sensor. It may take up to 10 min for all vehicle systems to power down.
  1. Test for less than 10 Ω between the low reference circuit terminal 1 and ground. ⇒ If 10 Ω or greater 2.1. Test circuit 407 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 2.2. Replace the K9 Body Control Module ⇓ If less than 10 Ω
  2. Ignition ON/Vehicle in Service Mode. Test for 4.8–5.2 V between the signal circuit terminal 2 and ground. ⇒ If less than 4.8 V 3.1. Test circuit 6137 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Test circuit 6137 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 3.3. Replace the K9 Body Control Module ⇒ If greater than 5.2 V 3.1. Test circuit 6137 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 3.2. Replace the K9 Body Control Module ⇓ If between 4.8–5.2 V
  3. Test or replace the B39 Air Conditioning Evaporator Air Temperature Sensor.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  5. Verify the DTC does not set. ⇒ If the DTC sets Replace the K9 Body Control Module. ⇓ If the DTC does not set
  6. All OK Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. HVAC Component Replacement Reference Control Module References for control module replacement, programming and setup