Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2004TAHOE 4WD V8-5.3L VIN TREPAIR AND DIAGNOSISENGINE, COOLING AND EXHAUSTCOOLING SYSTEMTESTING AND INSPECTIONSCAN TOOL TESTING AND PROCEDURESSCAN TOOL DATA DEFINITIONS
2004 Chevrolet Tahoe 4WD V8-5.3L VIN T
Scan Tool Data Definitions
2004 Chevrolet Tahoe 4WD V8-5.3L VIN TSECTION Scan Tool Data Definitions
Scan Tool Data Definitions
Check Coolant Temp-Range: ON/OFF: This output refers to the commanded state of the Check Coolant Temp message located in the message center. The message will be added to the message center display based on the engine coolant temperature that is sent to the Instrument Cluster as a class 2 message from the PCM. If the engine temperature is greater than 121°C (250°F) the message will be added to the message center, unless the Check Engine Temp message has been added to the message center, and removed when the engine temperature is less than 118°C (245°F).
Check Engine Temp-Range: ON/OFF: This output refers to the commanded state of the Check Engine Temp message located in the message center. The message will be added to the message center display based on the engine coolant temperature that is sent to the Instrument Cluster as a class 2 message from the PCM. If the engine temperature is greater than 128°C (262°F) the message will be added to the message center and removed when the engine temperature is less than 125°C (257°F).
Coolant Level Switch-Range: Low/OK: This parameter indicates when the engine coolant level is low. The scan tool displays Low when the PCM detects the engine coolant level switch is open.
ECT-Range: -40°C to +150°C (-40°F to +302°F): The PCM applies 5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the engine temperature changes. When the sensor is cold (internal resistance high), the PCM senses a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine
Displayed Coolant Temperature-Range: 32 - 127°C (89 - 260°F): This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant temperature gauge. This data may differ from the monitored coolant temperature for a period of time due to filtering. The data may also differ from the monitored coolant temperature when coolant temperature is not in the range of 71 - 127°C (160 - 260°F) since the display is limited to these values. If a Class 2 communication failure occurs, this data will be at the minimum value of 32°C (89°F).
Low Coolant-Range: ON/OFF: This output refers to the command state of the Low Coolant message located in the message center. ON is displayed when the Instrument Cluster is commanding the Low Coolant message ON. OFF is displayed when the Instrument Cluster is not commanding the Low Coolant message ON. The Instrument Cluster will display the Low Coolant message when the Instrument Cluster receives a class 2 serial data message from the PCM.
Monitored Coolant Temperature-Range: 40 - 215°C (40 - 419°F): This data is the clusters measurement of the engine coolant temperature as provided by the PCM on the Class 2 serial data line.
Reduced Engine Power-Range: ON/OFF: This output refers to the commanded state of the Reduced Engine Power message located in the message center. On is displayed when the Instrument Cluster is commanding the Reduced Engine Power message ON. OFF is displayed when the Instrument Cluster is not commanding the Reduced Engine Power message ON. The Instrument Cluster will display the Reduced Engine Power message when the Instrument Cluster receives a class 2 serial data message from the PCM when the engine temperature reaches 132°C (270°F).
Check Coolant Temp-Range: ON/OFF: This output refers to the commanded state of the Check Coolant Temp message located in the message center. The message will be added to the message center display based on the engine coolant temperature that is sent to the Instrument Cluster as a class 2 message from the PCM. If the engine temperature is greater than 121°C (250°F) the message will be added to the message center, unless the Check Engine Temp message has been added to the message center, and removed when the engine temperature is less than 118°C (245°F).
Check Engine Temp-Range: ON/OFF: This output refers to the commanded state of the Check Engine Temp message located in the message center. The message will be added to the message center display based on the engine coolant temperature that is sent to the Instrument Cluster as a class 2 message from the PCM. If the engine temperature is greater than 128°C (262°F) the message will be added to the message center and removed when the engine temperature is less than 125°C (257°F).
Coolant Level Switch-Range: Low/OK: This parameter indicates when the engine coolant level is low. The scan tool displays Low when the PCM detects the engine coolant level switch is open.
ECT-Range: -40°C to +150°C (-40°F to +302°F): The PCM applies 5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the engine temperature changes. When the sensor is cold (internal resistance high), the PCM senses a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine
Displayed Coolant Temperature-Range: 32 - 127°C (89 - 260°F): This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant temperature gauge. This data may differ from the monitored coolant temperature for a period of time due to filtering. The data may also differ from the monitored coolant temperature when coolant temperature is not in the range of 71 - 127°C (160 - 260°F) since the display is limited to these values. If a Class 2 communication failure occurs, this data will be at the minimum value of 32°C (89°F).
Low Coolant-Range: ON/OFF: This output refers to the command state of the Low Coolant message located in the message center. ON is displayed when the Instrument Cluster is commanding the Low Coolant message ON. OFF is displayed when the Instrument Cluster is not commanding the Low Coolant message ON. The Instrument Cluster will display the Low Coolant message when the Instrument Cluster receives a class 2 serial data message from the PCM.
Monitored Coolant Temperature-Range: 40 - 215°C (40 - 419°F): This data is the clusters measurement of the engine coolant temperature as provided by the PCM on the Class 2 serial data line.
Reduced Engine Power-Range: ON/OFF: This output refers to the commanded state of the Reduced Engine Power message located in the message center. On is displayed when the Instrument Cluster is commanding the Reduced Engine Power message ON. OFF is displayed when the Instrument Cluster is not commanding the Reduced Engine Power message ON. The Instrument Cluster will display the Reduced Engine Power message when the Instrument Cluster receives a class 2 serial data message from the PCM when the engine temperature reaches 132°C (270°F).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.