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Temperature Parameters


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 logic module by the coolant temperature sensor (CTS). The CTS is a thermistor installed in the engine coolant passages. The logic module 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

For most 1989 vehicles and later (except Turbo II models), 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 for some 1987-88 vehicles 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 logic module 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.

Ambient temperature is not displayed for most 1989 models.


AMBIENT AIR TEMPERATURE VOLTAGE

AMB TEMP(V) - X.X RANGE: 0 to 5.1 volts

For some 1987-88 vehicles, ambient temperature (AMB TEMP) voltage is a direct voltage reading from the ambient air temperature sensor. Sensor voltage and temperature are inversely related. Low temperature produces a high voltage signal; high temperature produces low voltage.

Ambient temperature is not displayed for most 1989 and later models.


CHARGE AIR TEMPERATURE

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

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

These analog parameters for 1985 and later port-injected vehicles indicate the temperature of the air/fuel charge inside the intake manifold. A thermistor temperature sensor is installed in the manifold, and the logic module 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 logic module substitutes charge temperature readings for coolant temperature values. This occurs in the "Limp-in" mode.


CHARGE AIR TEMPERATURE VOLTAGE

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

For 1985 and later port-injected vehicles, charge temperature (CHARGE TEMP) voltage is a direct voltage reading from the air/fuel charge temperature sensor. Sensor voltage and temperature are inversely related. Low temperature produces a high voltage signal; high temperature produces low voltage.


THROTTLE BODY TEMPERATURE

T-BODY TEMP(°F) - XXX RANGE: -40 to 389°

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

These analog parameters indicate the fuel temperature in the throttle body on 1986 and later low-pressure throttle body injection systems. A thermistor temperature sensor is installed in the throttle body fuel passage, and the logic module converts sensor voltage signals to fuel 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 throttle body temperature sensor is basically the same kind of thermistor as other temperature sensors. With a low-pressure throttle body injection (TBI) system, fuel may boil in the throttle body during a hot-soak period. At engine start-up, the logic module compares coolant temperature to throttle body fuel temperature. If fuel temperature is above a programmed value, the logic module increases injector pulse width during starting to purge fuel vapors from the injectors. Throttle body temperature affects pulse width only during starting, not at any other time.


THROTTLE BODY TEMPERATURE VOLTAGE

T-BODY TEMP(V) - X.X RANGE: 0 to 5.1 volts

For 1986 and later low-pressure throttle body injection systems, throttle body temperature (T-BODY TEMP) voltage is a direct voltage reading from the fuel temperature sensor in the throttle body. Sensor voltage and temperature are inversely related. Low temperature produces a high voltage signal; high temperature produces low voltage.


FUEL INJECTOR TEMPERATURE

INJ TEMP(°F) - XXX RANGE: -40 to 389°

INJ TEMP(°C) - XXX RANGE: -40 to 199°

INJ TEMP(v) - X.X RANGE: 0 to 5.1 volts

The scanner displays these analog parameters for 1988 and later throttle body injection (TBI) V-6 and V-8 truck engines. The INJ TEMP parameters indicate the same conditions for a truck engine that T-BODY TEMP parameters (described above) indicate for a passenger car engine


RADIATOR FAN RELAY

RAD FAN RELAY - XXX RANGE: ON - OFF

On some 1989 and later vehicles, RAD FAN RELAY is a discrete parameter that indicates whether or not the logic module 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.



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