PM620, PM622, PM820, PM822 and PM825 Cold Planers Electronic System Solenoid Return - Test Caterpillar


Solenoid Return - Test
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1.1. Transmission ECM
2.1. Diagnostic Trouble Code Procedure

Transmission ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the solenoid return lines of the machine.

Table 1
Transmission ECM 1 (MID 81) 
DTC  Code Description  System Response 
3942-4  Drive Pump Solenoid Return : Voltage Below Normal  This diagnostic code is active as a result of a short circuit to ground. A repair of the circuit is required. The "propel" is disabled when this fault is active. After the fault is corrected, the machine will "propel" normally. 

The solenoid is used to shutoff, release, distribute, or mix fluids on the machine. Generally, multiple solenoids are located together on a manifold. The solenoid converts electrical energy into magnetic energy, moving a spool located inside the housing of the valve. A spring is used to hold the spool in position until the solenoid is energized.

The magnetic force that acts on the valve spool is created when a coil inside the solenoid is energized.

Possible causes for an FMI 4 Diagnostic Code are:

  • There is an open in the circuit.

  • The harness is shorted to ground.

  • The solenoid has failed.

  • The ECM has failed. A failure of the ECM is unlikely.


Illustration 1g06028550
Illustration of the "Propel Reverse and Forward Solenoid Return Circuit".

Note: The diagram above is a simplified schematic of the electrical circuit. The schematic is electrically correct. However, not all the possible harness connectors are shown.Refer to the appropriate media number below for the complete Electrical Schematic: (S/N: JCF; LH9; 8RF; EL6) Machines refer to Electrical Schematic, UENR6397. (S/N: JB9; JFC; LB8; FG4; TPH; XS6) Machines refer to Electrical Schematic, UENR6398. (S/N: JB7; HN8; HC8; RL3; H6S; 626) Machines refer to Electrical Schematic, UENR8363. (S/N: SL8; TLZ; ESE; AK5; AN8; EE2; E8S; 3C6; 627) Machines refer to Electrical Schematic, UENR8362.The schematic will illustrate locations for all the electrical components and harness connectors that are installed on the machine.

Diagnostic Trouble Code Procedure

Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. Check the wiring harness for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.

Table 2
FMI 4 Troubleshooting 
Troubleshooting Test Steps  Values  Results 
1. Check The Machine Harness For An Open

A. Turn the key start switch and the disconnect switch OFF.

B. Disconnect the solenoid from the machine harness.

C. Disconnect the harness connectors at the ECM.

D. Connect a jumper wire between the signal contact and return contact at the solenoid harness connector.

E. At the ECM side of the machine harness, measure the resistance between the signal and return contact. 

Each reading is less than 5 Ω. 
OK - The reading is less than 5 Ω, the harness is correct.

Proceed to Test Step 2.

NOT OK - The reading is greater than 5K Ω. There is an open in machine harness.

Repair: The open is in the signal wire or the return wire. Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 3. 
2. Check The Harness For A Short To Ground

A. The key start switch and disconnect switch remain OFF.

B. The ECM and solenoid remain disconnected from the machine harness.

C. Remove the jumper wire that was installed in the previous Test Step.

D. Measure the resistance between the signal contact and frame ground. Record the measurement.

E. Measure the resistance between the return contact and frame ground. Record the measurement. 

Each reading is greater than 5K Ω. 
OK - The reading is greater than 5K Ω, the harness is correct.

Proceed to Test Step 3.

NOT OK - The reading is less than 5 Ω. There is a short in the machine harness.

Repair: The short is between the wires with the low-resistance measurement. Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 3. 
3. Check If The Diagnostic Code Remains

A. Reconnect all harness connectors. Return machine to normal operating condition.

B. Turn the key start switch and the disconnect switch ON.

C. Clear all diagnostic codes.

D. Operate the machine.

E. Stop the machine and engage the safety lock lever.

F. Check if the diagnostic code is active. 

The diagnostic code is no longer present. 
OK - The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation.

STOP.

NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement.

Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time.

Follow the steps in "ECM - Replace" if the ECM needs to be replaced.

STOP. 

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