308E2 CR Mini Hydraulic Excavator Operator Control Switch (Switch to Ground) - Test Caterpillar


Operator Control Switch (Switch to Ground) - Test
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308E2 CR Mini Hydraulic Excavator [M0068872]
ELECTRICAL AND STARTING SYSTEM
SWITCH GP
308E2 CR Mini Hydraulic Excavator Operator Control Switch (Switch to Ground) - Test
1.1. Machine ECM
2.1. Diagnostic Trouble Code Procedure
3.2. FMI 2

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the operator control switch of the machine.

Table 1
Machine ECM (MID 299) 
J1939  CDL  Code Description  System Response 
  91-2  Throttle Position Switch: Data Erratic, Intermittent, Incorrect  Machine is forced into low idle. 

Possible causes for an FMI 2 diagnostic code are:

  • A short circuit exists.

  • An open circuit exists.

  • The switch has failed.

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


Illustration 1g06037084
Schematic of the Operator Control Switch

Note: The diagram above is a simplified schematic of the Machine ECM and the Operator Control Switch connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR3899, Electrical Schematic, UENR6992, or Electrical Schematic, UENR7463 for the complete schematic.

Table 2
Switch Operation for the Throttle Switch (CID 91) 
Switch Position  Contacts Shorted to COM Ground Pin 1 
 
1 (Turtle)       
   
     
   
 
   
     
   
 
10 (Rabbit) 

Diagnostic Trouble Code Procedure

Table 3
Required Tools 
Tool  Part Number  Description  Qty 
T1  146-4080(1)  Digital Multimeter Group 
8T-3224 Needle Tip Group 
7X-1710 Multimeter Probe Group 
8T-8726 Cable Assembly (Three Pin) (3-Pin Breakout) 
T2  JERD2129  Cat® Electronic Technician (Cat ET) 
Windows-based PC 
538-5051 Communication Adapter Gp 
T3  6V-4148  Connector Repair Kit (Sure Seal) 
T4  190-8900  Connector Field Repair Kit (Deutsch) 
T5  175-3700  Connector Repair Kit Deutsch DT 
(1) This multimeter can use an RS232C cable to connect to a Laptop computer or Dataview tool gp for troubleshooting.

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. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.

  1. Identify the active FMI code associated with the components.

  2. Determine which code is present and use the list below to determine which procedure to follow.

  • FMI 2 diagnostic code, proceed to "FMI 2".

FMI 2

Table 4
Check the Ground Source for the Switch 
Troubleshooting Test Steps  Values  Results 
1. Turn the key switch OFF.

2. All harness connectors remain the same.

3. At the switch, measure the resistance between the ground contact and frame ground. 

The resistance is less than 5 Ω. 
Result: The resistance is less than 5 Ω.

Proceed to "Check the Operation of the Switch".

Result: The resistance is greater than 5k Ω.

Repair: The switch does not have a good ground source. Replace the harness between the switch and the ground source.

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

Proceed to "Check the Harness for an Open". 

Table 5
Check the Operation of the Switch 
Troubleshooting Test Steps  Values  Results 
1. Turn the key switch OFF.

2. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation. 

The switch operates correctly. 
Result: The switch is operating correctly.

Proceed to "Check the Harness for an Open".

Result: The switch is not operating correctly. The switch has failed

Repair: Replace the switch.

Proceed to "Check if the Diagnostic Code Remains". 

Table 6
Check the Harness for an Open 
Troubleshooting Test Steps  Values  Results 
1. Turn key start switch and disconnect switch OFF.

2. Disconnect the switch from the machine harness.

3. Disconnect the machine harness connector at the ECM.

4. Check the continuity between the harness switch connector and the machine ECM harness connector for each wire. 

The resistance is less than 5k Ω. 
Result: The circuit is correct.

Proceed to "Check the Harness for a Short".

Result: The resistance is greater than 5kΩ. The circuit is open.

Repair: Repair or replace the machine harness.

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

Proceed to "Check if the Diagnostic Code Remains". 

Table 7
Check the Harness for a Short 
Troubleshooting Test Steps  Values  Results 
1. The key switch remains OFF.

2. All harness connectors remain disconnected.

3. Remove the jumper wire installed in the previous step.

4. At the machine harness connector for the ECM, measure resistance between the signal contacts and all other contacts of the machine harness connector at the ECM. 

The resistances are greater than 5k Ω. 
Result: The resistance is greater than 5k Ω. The harness circuit is correct.

Proceed to "Check if the Diagnostic Code Remains".

Result: The resistance less than 5 Ω.

Repair: A short exists in the harness between the signal circuit and the wire with the low-resistance reading. 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 "Check if the Diagnostic Code Remains". 

Table 8
Check if the Diagnostic Code Remains 
Troubleshooting Steps  Values  Results 
1. Inspect the harness connectors and clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

3. Turn key switch and disconnect switch ON.

4. Operate the machine.

5. Check if diagnostic code is active. 

Diagnostic code is no longer present. 
Result: 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

Result: 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 this component, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may greatly effect repair time.

Follow the steps in Troubleshooting, "Electronic Control Module (ECM) - Replace" if the ECM needs to be replaced.

STOP 

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