0439191 JOHNSON THROTTLE BODY, Lower

Illustration 1 g00889896
Schematic for throttle switch
Table 1
Correlation Between Throttle Switch Position and Status of the Throttle Inputs    
Throttle Switch Position    Desired Engine Speed    Status on Cat ET    
"Throttle Input #1" "Throttle Input #2"    "Throttle Input #3"    "Throttle Input #4"    
1     800     On     Off     Off     Off    
2     1000     On     On     Off     Off    
3     1170     Off     On     Off     Off    
4     1340     Off     On     On     Off    
5     1510     On     On     On     Off    
6     1680     On     Off     On     Off    
7     1850     Off     Off     On     Off    
8     2000     Off     Off     On     On    
9     2100     On     Off     On     On    
10     2200     On     On     On     On    Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect ECM connector J1/P1, machine connector J3/P3, and the throttle switch connector P118. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for corrosion, abrasion, and pinch points from the throttle switch to the ECM.Expected Result:All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 2. Check "Throttle Cab Switch Position" on Caterpillar Electronic Technician (Cat ET)
Connect Cat ET at the service tool connector.
Turn the keyswitch to the ON position.
Observe the status of the throttle switch and the throttle inputs on Cat ET while you operate the throttle switch in each position.Expected Result:The status on Cat ET corresponds with the information in Table 1.Results:
OK - The throttle switch is functioning properly at this time.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent. Stop.
Not OK - Record the suspect input. Proceed to Test Step 3.Test Step 3. Jumper the Switch Input at the Throttle Switch Connector
Disconnect the throttle switch connector P118.
Observe the status of the suspect throttle input on Cat ET.
Use a suitable piece of wire to short P118:1 (Digital Return) to the terminal for the suspect throttle input at throttle switch connector P118.
Observe the status of the suspect throttle input on Cat ET.
Remove the wire short.Expected Result:The status of the suspect throttle input should be "Off" when throttle switch connector P118 is disconnected. The status should be "On" when the wire short is installed.Results:
OK - The harness and the ECM are OK.Repair: Replace the throttle switch.Verify that the repair eliminates the problem. Stop.
Not OK - Proceed to Test Step 4.Test Step 4. Check for Shorts in the Harness
Turn the keyswitch to the OFF/RESET position.
Disconnect ECM connector J1/P1 and throttle switch connector P118.
Measure the resistance between engine ground and the terminal for the suspect throttle input at throttle switch connector P118.
Measure the resistance between the terminal for the suspect throttle input at throttle switch connector P118 and the remaining terminals at the connector.Expected Result:Resistance should be greater than 20,000 Ohms for each reading.Results:
OK - Proceed to Test Step 5.
Not OK - There is a short in the harness between the ECM and the throttle switch.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 5. Check Resistance through the Harness
Illustration 2 g00889924
ECM connector P1 (ECM side)
Use a suitable piece of wire to short P118:1 (Digital Return) to the terminal of the suspect throttle input at throttle switch connector P118.
Measure the resistance between P1:18 (Digital Return) and the terminal for the suspect throttle input at ECM connector P1.Expected Result:Resistance should be less than 10 Ohms.Results:
OK - Proceed to Test Step 6.
Not OK - There is an open circuit or excessive resistance in the harness.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 6. Check the Harness and the ECM