P1239 Engine Oil Temperature Too Low

P1239 code - This diagnostic runs the following conditions are meet the model predicted oil temperature at engine start is less than 58°C (136.4°F) to initiate the monitor. The monitor will stop when the model predicted engine oil temperature is greater than 88°C (190.4°F).


P1239


The set condition this DTC the actual engine oil temperature is below the model predicted temperature by more than 104°F (40°C) for three minutes. Defaul action the MIL light illuminate.

Possible causes P1239 code

- Engine oil
- Cooling system not operating to specification
- High resistance in the EOT  signal circuit
- High resistance in the sensor ground circuit
- Engine Oil temperature sensor
- Powertrain Control Module (PCM)

Diagnostic test P1239 code

Step 1. Check for an active DTC
Diagnose any other engine oil temperature (EOT) sensor DTCs before continuing. Turn the ignition off, allow the vehicle to sit with the ignition off in an envronment where the temperature will allow the oil temperature to cool down below the engine start model predicted temperature. With the scan tool read DTC s and record on the repair order.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Engine Oil
The following conditions must be checked:
  • Low engine oil
  • Engine mechanical tolerances out of specification
  • Engine Oil pressure out of specifiation
  • Engine Oil meets OEM specification
  • Deteriorated or dirty oil
  • Engine oil contaminated (i.e., coolant and/or fuel)
  • Cooling system not operating to specification
Were any of the above conditions found?

Yes, repair as necessary.
No, go to step 3.

Step 3. Check for high resistance in the EOT signal circuit
Turn the ignition off, disconnect the PCM harness connector. Measure the resistance of the EOT signal circuit between the EOP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 4.
No, repair the EOT signal circuit for high resistance

Step 4. Check for high resistance in the sensor ground circuit
Measure the resistance of the sensor ground circuit between the Engine Oil Sensor connector and PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 5
No, repair the sensor ground circuit for high resistance.

Step 5. Engine Oil temperature
Reconnect the PCM harness connector. Turn the ignition on, with the scan tool read the engine oil temperature sensor voltage. The sensor voltage should be approximately 5.0 volts (plus or minus 1 volts) with the connector disconnected. Connect a jumper between the EOT signal circuit and the sensor harness connnector. With the scan tool, read the Engine Oil Temperature sensor voltage. The sensor voltage should be 0.0 volts (plus or minus 1 volts) with the jumper in place.

Is the scan tool display the voltage as described above?

Yes, verify that there is god pin to terminal contact in the EOT sensor and Powertrain Control Module connectors. Replace the engine oil temperature sensor if no problems were found with the connectors.

No, go to step 6.

Step 6. Check related PCM and component connections

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