2007 Liberty KJ Factory Service Manual 21 - TRANSMISSION AND TRANSFER CASE

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 Engine RPM Signal circuit. The calculated engine RPM is also compared to a minimum and a maximum value.



Possible Causes
  
RELATED ENGINE DTC'S PRESENT
  
ENGINE RPM SIGNAL CIRCUIT OPEN
  
ENGINE RPM SIGNAL CIRCUIT SHORT TO GROUND
  
ENGINE RPM SIGNAL CIRCUIT SHORT TO VOLTAGE
  
TRANSMISSION CONTROL MODULE
  
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.


Ignition on, engine not running.
With the scan tool, read all Engine DTCs. This includes any active or stored or one trip DTCs.

Are there any engine RPM related DTCs present?

Yes


No

2. CHECK IF THE DTC IS CURRENT


Ignition on, engine not running.
With the scan tool, check the Starts Since Set counter for this DTC.

Is the Starts Since Set counter 2 or less?

Yes


No

3. CHECK THE (K244) ENGINE RPM SIGNAL CIRCUIT FOR AN OPEN

Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the ECM harness connector.
Measure the resistance of the (K244) Engine RPM Signal circuit between the TCM harness connector and the ECM harness connector.

Is the resistance above 5.0 ohms?

Yes


No

4. CHECK THE (K244) ENGINE RPM SIGNAL CIRCUIT FOR A SHORT TO GROUND

Measure the resistance between ground and the (K244) Engine RPM Signal circuit.

Is the resistance below 5.0 ohms?

Yes


No

5. CHECK THE (K244) ENGINE RPM SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

Ignition on, engine not running.
Check the voltage of the (K244) Engine RPM Signal circuit.

Is the voltage above 0.5 volts?

Yes


No

6. CHECK THE TCM

Turn the ignition off to the lock position.
Replace and program the TCM per the Service Information.
Start the engine and allow the engine to idle for 6 minutes.
Check the voltage of the (K244) Engine RPM Signal circuit.

Does the DTC reset?

Yes


No

7. CHECK WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorted and open circuits.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes


No