P1115-GENERAL TEMPERATURE RATIONALITY





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The General Temperature Rationality looks at the outputs of the three temperature sensors and compare them under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and intake air temperature sensors will be compared. If two sensors agree but not the third, the third sensor is declared as irrational. If all three sensors are irrational the General Temperature Sensor Rationality is failed.

  • When Monitored:

    Ignition on and battery voltage greater than 10 volts.

  • Set Condition:

    Ambient Air, Engine Coolant, and Intake Air Temp sensor inputs are compared under cold start conditions. After start up the temp readings are monitored. If two of the three readings agree and the third doesn't, a DTC is stored. Two Trip Fault. Three good trips to turn off the MIL.


Possible Causes
  
EXCESSIVE RESISTANCE IN THE SENSOR SIGNAL CIRCUIT
  
EXCESSIVE RESISTANCE IN THE SENSOR GROUND CIRCUIT
  
TEMPERATURE SENSOR
  
PCM
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1.ACTIVE DTC



NOTE: All ECT, Intake Air, and Ambient Air Temperature Sensor codes must be diagnosed and repaired before continuing.


NOTE: In cold weather, this DTC could be set by a high powered block heater and no repair would be required.


NOTE: It may be necessary to test drive the vehicle to get the fault to an Active or Pending state because it takes two failed trips to set.



Is the DTC Active or Pending at this time?

Yes
  • Go To 2


No

2.TEMPERATURE SENSOR CIRCUIT





Is the temperature for each of the Sensors increasing properly?

Yes


No
  • Go To 3

3.TEMPERATURE SENSOR












Did the voltage reading start at 4.8 to 5.0 volts and decrease to 0 volts when the jumper wire was installed?

Yes


No
  • Go To 4

  • NOTE: Remove the jumper wire before continuing.


4.EXCESSIVE RESISTANCE IN THE TEMPERATURE SENSOR SIGNAL CIRCUIT










CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.





Is the resistance above 5.0 ohms.

Yes


No
  • Go To 5

5.EXCESSIVE RESISTANCE IN THE SENSOR GROUND CIRCUIT










Is the resistance above 5.0 ohms.

Yes


No
  • Go To 6

6.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.




Were there any problems found?

Yes


No