Pinpoint Test Y: Engine Oil Temperature Sensor: Description

Engine Oil Temperature (EOT) sensor is a thermistor type sensor that has a variable resistance that changes when exposed to different temperatures. When interfaced with Powertrain Control Module (PCM), it produces a 0-5 volt analog signal that will deduce temperature.

• Cranking Fuel Quantity/Timing Control
  
  EOT sensor signal is used to determine timing and quantity of fuel required to optimize starting over all temperature conditions.
• Idle Speed
  
  At oil temperatures less than 158°F (70°C), low idle is incrementally increased to a maximum of 950 RPM.
• Temperature Compensation
  
  Fuel quantity and timing is controlled throughout total operating range to ensure adequate torque and power is available.
• Glow Plug Control
  
  Glow plug relay and WAIT TO START light ON time are controlled by engine oil temperature.

An EOT sensor signal that is detected out of range (high or low) by PCM will cause PCM to ignore EOT sensor signal and assume an engine oil temperature of -29°F (-34°C) for starting and a temperature of 212°F (100°C) for engine-running conditions. The CHECK ENGINE light will also be illuminated as long as condition exists. DTC 0197 indicates EOT sensor circuit input low. DTC 0198 indicates EOT sensor circuit input high. DTC 0196 indicates engine oil temperature less than 165°F (74°C) or above 240°F (116°C) during KOER CYLINDER CONTRIBUTION SELF-TEST (self-test access denied).

Perform this test only when directed here by QUICK TEST. Glow plug relay and glow plug light "On" time are controlled by engine oil temperature. This test is intended to diagnose:

• EOT sensor.
• Wiring harness circuits (EOT and SIG RTN).
• Faulty Powertrain Control Module (PCM).

Fig 1: Identifying EOT Sensor Circuit Checks (1 Of 2)

Courtesy of FORD MOTOR CO.

Fig 2: Identifying EOT Sensor Circuit Checks (2 Of 2)

Courtesy of FORD MOTOR CO.