Engine Oil Temperature (EOT) Sensor

Signal Functions

The Engine Oil Temperature (EOT) sensor is a thermistor type sensor that has a variable resistance which changes when exposed to different temperatures. When interfaced with PCM it produces a 0 to 5 volt analog signal that will measure engine oil temperature.

Cranking Fuel Quantity/Timing Control

The EOT signal is used to determine the timing and quantity of fuel required to optimize starting over all temperature conditions.

Temperatures Compensation

Fuel quantity and timing is controlled throughout the total operating range to compensate for oil viscosity changes due to temperature variations and insure that adequate torque and power is available.

Idle Speed (Vehicles with Automatic Transmission)

At oil temperatures below 32°F (0°C), low idle is incrementally increased to a maximum of 1200 RPM at - 20°F (-30°C).

Idle Speed (Vehicles with Manual Transmission)

At oil temperatures below 95°F (35°C), low idle is incrementally increased to a maximum of 1200 RPM at - 20°F (-30°C).

Fault Detection/Management

An EOT signal that is detected out of range high or low by the PCM will cause the PCM to ignore the EOT signal and default to a 212°F (100°C) value for engine oil temperature. The CHECK engine lamp will also be illuminated as long as the fault condition exists. The NGS tool will display a fixed PID value of 212°F (100°C) when EOT is in default.

NOTE: After removing connector always check for damaged pins, corrosion, loose terminals etc.

Connector Checks to Ground (B-) (Check with Sensor Connector Disconnected and Ignition key off, all accessories off)

Test Points	Spec	Comments
A to Grd.	< 5 ohms	Resistance to chassis ground, check with key OFF, if > than 5 ohms the harness is open
B to Grd.	> 1000 ohms	Resistance less than 1000 ohms indicates a short to ground

Connector Voltage Checks (Check with Sensor Connector Disconnected and Ignition Key On)

Test Points	Spec.	Comments
B to Grd.	4.8 - 5.0 v	Pull up voltage, if no or low voltage, circuit has open or high resistance or short to ground
A to Grd.	0 - .25 v	If greater than .25 volts signal ground is open or shorted to VRef or battery.

Harness Resistance Checks (Check with breakout box installed on engine harness only)

Test Points	Spec	Comments
#91 to A	< 5 ohms	Resistance from harness connector to 104 pin connector - Signal ground
#38 to B	< 5 ohms	Resistance from harness connector to 104 pin connector - EOT Signal

Operational Signal Checks (Check with breakout box installed in line with the PCM)

Test Points (+) #38 to (-) #91		Temp. °C	Resistance	Comments
Voltage	Temp. °F
0.53 v	248	120	1.19 K ohms
0.96 v	205	96	2 K ohms
1.37 v	176	80	3.84 K ohms
4.37 v	32	0	7.21 K ohms
4.60 v	-5	-20	8.22 K ohms

Diagnostic Trouble Code Descriptions

Circuit Faults:
0197 = Signal was less than .04 volts for more than 0.2 seconds.
0198 = Signal voltage was greater than 4.9 volts for more than 0.2 seconds.
0195 = Engine oil temperature less than 158° F (70° C) during KOER test (Access denied) or engine oil temperature greater than 242° F (117° C) during KOER test (aborts Test).