P0725-ENGINE SPEED SENSOR CIRCUIT

For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The Transmission Control System calculates the engine RPM by directly reading the engine crank position sensor. It compares the calculated value to the engine speed sensor signal transmitted from the Engine Control System over the controllers internal BUS. The calculated engine RPM is also compared to a minimum and a maximum value. Note: Due to the integration of the Powertrain Control Module (PCM) and Transmission Control Module (TCM), BUS communication between the modules is internal and unserviceable.


  • When Monitored:

    Continuously every 7 msec with the ignition on and engine running.

  • Set Condition:

    This DTC will set when the calculated engine speed is less than 390 RPM with the engine running, or greater than 8000 RPM, for the period of 2.0 seconds. The PCM will place the Transmission in Limp-in when this DTC is set. Note: This is not a Transmission Input Speed Sensor DTC.


Possible Causes
  
RELATED ENGINE DTCS PRESENT
  
CRANK POSITION SENSOR OR WIRING
  
POWERTRAIN CONTROL MODULE
  

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)



Diagnostic Test

1.CHECK FOR RELATED ENGINE DTCS

NOTE: This is not a Transmission Input Speed Sensor DTC.





Are there any engine RPM related DTCs present?

Yes


No
  • Go To 2

2.CHECK IF DTC IS CURRENT






NOTE: Refer to all engine DTCs first in the following question.



Pick the answer below that best describes your findings, (this includes one trip failures).

Transmission DTC P0725 set
  • Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Also check the Crank Position sensor and wiring. Pay particular attention to all power and ground circuits. If no problems are found, replace the PCM per the Service Information. With the scan tool, perform QUICK LEARN.
  • Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)


Engine DTC set


No DTC set at all
  • Go To 3

3.CHECK WIRING AND CONNECTORS






Were there any problems found?

Yes


No
  • Test Complete.