Temperature Parameters

NOTE: These parameters indicate the temperature of the engine coolant, the intake air, the ambient air, and the fuel

COOLANT TEMPERATURE
COOLANT (°F) - XXX RANGE: -40 to 389°

COOLANT (°C) - XXX RANGE: -40 to 199°

The coolant temperature is an analog parameter, supplied to the Powertrain Control Module (PCM) by the coolant temperature sensor (CTS). The CTS is a thermistor installed in the engine coolant passages. The PCM converts CTS voltage signals to temperature readings. You can change the measurement units on the scanner from degrees Fahrenheit (°F) to degrees Celsius (°C). The preset measurement is F.

Typical readings with a fully warmed engine running at idle are 185 to 220° F (85 to 1O5°C). A reading of -40° F or -40° C may indicate an open in the sensor or the sensor circuit. A reading above 366° F or 185° C may indicate a short in the sensor or the sensor circuit.

COOLANT TEMPERATURE VOLTAGE
COOLANT TEMP(V) - X.X RANGE: 0 to 5.1 volts

The scanner displays the voltage signal from the coolant temperature sensor Sensor voltage and temperature are inversely related. Low temperature produces a high voltage signal; high temperature produces low voltage.

AMBIENT AIR TEMPERATURE
AMB TEMP(°F) - XXX RANGE: -40 to 389°

AMB TEMP(°C) - XXX RANGE: -40 to 199°

These analog parameters indicate the temperature of the ambient air in the engine compartment. A thermistor temperature sensor is installed in the outside of the throttle body. The PCM converts sensor voltage signals to air temperature readings.

You can change the measurement units on the scanner from degrees Fahrenheit (°F) to degrees Celsius (°C). The preset measurement is F.

CHARGE AIR TEMPERATURE
CHARGE TEMP(°F) - XXX RANGE: -40 to 389°

CHARGE TEMP(°C) - XXX RANGE: -40 to 199°

These analog parameters indicate the temperature of the air charge inside the intake manifold. A thermistor temperature sensor is installed in the manifold, and the PCM converts sensor voltage signals to charge temperature readings.

You can change the measurement units on the scanner from degrees Fahrenheit (°F) to degrees Celsius (°C). The preset measurement is F.

The charge temperature sensor is the same kind of thermistor as the coolant temperature sensor (CTS). If the CTS fails, the PCM substitutes charge temperature readings for coolant temperature values.

CHARGE AIR TEMPERATURE VOLTAGE
CHARGE TEMP(V) - X.X RANGE: 0 to 5.1 volts

Charge temperature (CHARGE TEMP) voltage is a direct voltage reading from the air charge temperature sensor. Sensor voltage and temperature are inversely related. Low temperature produces a high voltage signal; high temperature produces low voltage.

RADIATOR FAN RELAY
RAD FAN RELAY - XXX RANGE: ON - OFF

RAD FAN RELAY is a discrete parameter that indicates whether or not the PCM has commanded the engine electric cooling fan to turn on. It should read ON whenever the air conditioning is operating or the coolant temperature is high enough to require fan operation.