Diagnostic Test - Hydraulic Pump Faults

IMPORTANT DTC DESCRIPTION INFORMATION:  The DTC descriptions with T-CASE MOTOR and T-CASE CLUTCH PRESSOR SENSOR called out are used for the REAR DRIVE MODULE HYDRAULIC PUMP and PRESSURE SENSOR on this system.

TECH TIPS: 

• If the DTCM is replaced, the Restore Vehicle Configuration procedure must be performed  for the system to operate correctly and not set a configuration mismatch DTC. A configuration mismatch can also set if an incorrect smart actuator is installed.

COMPLETE SYSTEM DIAGNOSTICS (C1415-92, C1440-64):  The pressure reading, hydraulic pump control circuit voltages and pump current values can be monitored in the scan tool data for most applications. The hydraulic pump and sensor are referred to as the DTCM ECC Motor and Pressure Sensor in the scan tool data reads.  The RDM Motor data reads refer to the RDM smart actuator shift fork (if equipped).

1. Perform an initial check of the system with the ignition on and the pump motor commanded off to verify the sensor signal and DTCM operation. Turn the ignition on, vehicle in PARK. Using the scan tool, monitor the pressure sensor reading, hydraulic pump duty cycle and current data for 5 minutes. A lab scope can be used to monitor the current draw on the pump motor circuits as well as using the scan tool. There should be no current flow and the pressure sensor signal data should show less than 5.0 kPa.
   1. DTCM Current monitoring failure checks:  There are two ways the DTCM can fail and cause a fault. If the scan tool is showing a negative current draw reading, or if there is current flow above 0.5 amps with the pump commanded off (0% duty cycle), the internal DTCM current sensor is faulty. If either condition is present, replace the DTCM in accordance with the service information.
   2. Pressure sensor check:  If the ECC Pressure Sensor reading is above 5.0kPa (0.73psi) with 0% duty cycle and no current flow, either the pressure sensor is drifted out of range or there is resistance in the pressure sensor circuitry.
      • Isolate and check the pressure sensor circuits for the high resistance, above 3.0 Ohms. If there is high resistance in one or more of the circuits, repair the resistance in the circuit. If all circuits test good, replace the pressure sensor and retest.
   3. If the initial readings are correct, continue testing in step 2. 
2. Turn the ignition on with the vehicle in PARK. Monitor the ECC Motor A and Motor B voltage on the scan tool. If not available on the scan tool, using a DVOM, back probe and check the voltage on motor A control and motor B control circuits. Both voltage readings should be approximately 2.8 volts with the pump not energized.
   1. If both circuits measure approximately 2.8 volts, continue testing is step 3. 
   2. If both circuits do not measure approximately 2.8 volts with the pump commanded off, perform the HYDRAULIC PUMP CIRCUIT FAULT SYSTEM DIAGNOSTICS  procedure below to check for pump circuit issues.
3. Check the hydraulic pump functionality. NOTE: This test step is being performed assuming that the hydraulic pump control circuits were good, with no opens or shorts.  Using the scan tool, monitor the hydraulic pump current draw, hydraulic pump duty cycle and pressure sensor readings. Start the engine and put the vehicle in DRIVE with the brake pedal pressed, (vehicle stopped). The hydraulic pump should now be commanded on. With the duty cycle at the lower range (approximately 8 - 12%) there should be some current flow (approximately 1 - 2 amps) and the pressure sensor should now show some pressure. Test drive the vehicle and operate the vehicle under moderate to heavy acceleration while monitoring the readings. As the duty cycle increases the amperage draw should increase significantly (to as much as 10 - 15 amps) and the pressure reading should increase accordingly.
   1. If the motor current and pressure sensor reading are low when the duty cycle is high it could indicate low RDM hydraulic fluid in the system or a faulty pump motor. Continue testing in step 4. 
   2. An excessively high current draw with low pressure could indicate a blocked pump, an internal short across the coil windings or the control circuits are shorted together. Continue testing in step 5. 
   3. If the motor current appears to be increasing with the duty cycle, but the pressure sensor is not increasing it indicates that the sensor is likely stuck. Replace the pressure sensor in accordance with the service information and retest.
4. The RDM assembly is filled with one fluid to lubricate the internal components and a separate hydraulic fluid to operate the clutches. The RDM hydraulic fluid is a fill for life fluid. The level should be full unless there is a leak at the hydraulic pump assembly or pressure sensor.
   1. If the RDM is leaking hydraulic fluid from the pump or sensor, repair the leak and verify that the RDM hydraulic fluid is filled to the proper level and bled properly. Refer to appropriate the service information for the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.
   2. If the system is not leaking, replace the hydraulic pump assembly in accordance with the service information. Refer to the appropriate service information for the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.
5. Turn the ignition off. Disconnect the hydraulic pump and DTCM harness connectors to isolate the circuits. Check for continuity between the motor A control circuit and motor B control circuit.
   1. If there is continuity present, repair the shorts between the circuits.
   2. If no continuity is present, replace the hydraulic pump in accordance with the service information. Refer to the appropriate service information for the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.

HYDRAULIC PUMP CIRCUIT FAULT SYSTEM DIAGNOSTICS (C140B-11, C140B-12, C140B-13): 

1. Turn the ignition on and the vehicle in PARK. The hydraulic pump should not be on. This can be verified by checking the pump current draw and pressure reading on the scan tool. Monitor the ECC Motor A and Motor B voltage on the scan tool. If not available on the scan tool, using a DVOM, back probe and check the voltage on motor A control and motor B control circuits. Both circuits should have approximately 2.8 volts with the pump motor off.
   1. If both circuits are measuring approximately 2.8 volts, continue testing in step 2. 
   2. If the motor A control circuit is measuring 3.6 volts and motor B control circuit is measuring 0 volts, it would indicate that one of the circuits is open. Continue testing in step 3. 
   3. If both circuits are reading battery voltage it would indicate one of the circuits is shorted to voltage.
      • Disconnect the harness connector and measure each circuit individually to determine which circuit is shorted to voltage.
   4. If one of the circuits is shorted to ground the voltage readings will be different based on which circuit is shorted to ground.
      • If both motor control circuits read 0 volts, it indicates that motor A control circuit is shorted to ground.
      • If motor A control circuit measures 0 volts and motor B control circuit measures approximately 1.3. volts, it indicates that motor B control circuit is shorted to ground.
      • An alternative method of testing is to isolate the circuits and check for continuity between ground and each motor control circuit. Repair the short to ground in the circuit that showed continuity.
2. Isolate the hydraulic pump control circuits by disconnecting the hydraulic pump harness connector at the RDM and the DTCM harness connectors. Check for continuity between the circuits to verify they are not shorted to together.
   1. If there is no continuity between the circuits, continue testing in step 3. 
   2. If there is continuity between the circuits, repair the short between the circuits.
3. Check the pump motor A and pump motor B circuits for an open or high resistance by isolating and load testing each circuit. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool, additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .

   Courtesy of CHRYSLER GROUP, LLC

   1. To verify that there is no resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. The voltage drop across the bulb should be equal to the voltage reading across the battery terminals if there is no resistance in the circuit being tested.
      • If either circuit fails the load testing, repair the circuit for an open or high resistance.
      • If both circuits pass the load test, continue testing in step 4. 
4. Check the hydraulic pump functionality. NOTE: This test step is being performed assuming that the pump motor control circuits have tested good, with no opens or shorts.  Using the scan tool, monitor the hydraulic pump current draw, hydraulic pump duty cycle and pressure sensor readings. Start the engine and put the vehicle in DRIVE with foot on the brake, (vehicle stopped). The hydraulic pump should now be commanded on. With the duty cycle at the lower range there should be some current flow (approximately 1 - 2 amps) and the pressure sensor should now show pressure. Operate the vehicle under heavy acceleration while monitoring the readings. As the duty cycle increases the amperage draw should increase significantly (to as much as 10 - 15 amps) and the pressure reading should increase accordingly.
   1. A low amperage draw and pressure sensor reading when the duty cycle increases could indicate low RDM hydraulic fluid in the system or a faulty pump motor. Continue testing in step 5. 
   2. An excessively high current draw could indicate a blocked pump, an internal short across the coil windings or the control circuits are shorted together. Continue testing in step 6. 
   3. If the current draw appears to be increasing with the duty cycle but the pressure sensor is not increasing it would indicate a stuck sensor signal. Replace the pressure sensor in accordance with the service information and retest.
5. The RDM assembly is filled with one fluid to lubricate the internal components and a separate hydraulic fluid to operate the clutches. The RDM hydraulic fluid is a fill for life fluid. The level should be full unless there is a leak at the hydraulic pump assembly or pressure sensor.
   1. If the RDM is leaking hydraulic fluid, repair the leak and verify that the RDM hydraulic fluid is filled to the proper level and bled properly. Refer to the appropriate service information for the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.
   2. If the system is not leaking, replace the hydraulic pump assembly in accordance with the service information. Perform the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.
6. Isolate the wiring and check for continuity between the control circuits before replacing the hydraulic pump. Turn the ignition off. Disconnect the hydraulic pump and DTCM harness connectors to isolate the circuits. Check for continuity between the motor A control circuit and motor B control circuit.
   1. If there is continuity present, repair the shorts between the circuits.
   2. If no continuity is present, replace the hydraulic pump in accordance with the service information. Perform the proper procedure to check the hydraulic fluid level and bleed the system. Retest system operation.