18710 1 Mercruiser CAP

Illustration 1 g00899227
Schematic
Illustration 2 g00899213
P2 ECM connector
Table 1
Throttle Switch Position    Desired Engine Speed    
1     850    
2     980    
3     1110    
4     1240    
5     1370    
6     1500    
7     1630    
8     1760    
9     1860    
10     1980    Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Inspect the J2/P2 ECM connector, theJ3/P3 machine connector, the J1/P1 Machine Control Module connector, and the throttle switch connector. 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 the Throttle Switch
Connect the Caterpillar Electronic Technician (Cat ET) to the service tool connector.
Turn the keyswitch to the ON position.
Ensure that the machine is not operating in the throttle backup mode.
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:Cat ET should display a duty cycle between 5 percent and 95 percent or Cat ET should display a throttle position between 0 percent and 100 percent.Results:
OK - The throttle switch is operating properly at this time. Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent. Stop.
Not OK - There is a problem with the circuit for the throttle switch. Proceed to Test Step 3.Test Step 3. Check the Throttle Command at the Machine Control Module
Turn the keyswitch to the ON position.
Ensure that the machine is not operating in the throttle backup mode.
Use a multimeter to monitor the percent duty cycle of the throttle command at P1:1 of the Machine Control Module. Adjust the throttle switch from the low idle position to the high idle position.Expected Result:At low idle, the duty cycle should be between 5 percent and 10 percent. At high idle, the duty cycle should be between 90 percent and 95 percent.Results:
OK - The throttle command is correct. Proceed to Test Step 4.
Not OK - The throttle command is not correct. There may be a problem with the throttle switch or the Machine Control Module.Repair: Refer to the System Operation Manual and the Testing and Adjusting Manual for the machine. Stop.Test Step 4. Check the Throttle Command at the ECM
Turn the keyswitch to the ON position.
Use a multimeter to monitor the percent duty cycle of the throttle command between ECM connector P2:31 (throttle command) and ECM connector P1:5 (-battery). Adjust the throttle switch from the low idle position to the high idle position.Note: Certain operating conditions may limit the percent duty cycle of the throttle. Refer to the System Operation Manual and the Testing and Adjusting Manual for the machine for information on the machine controls.Expected Result:At low idle, the duty cycle should be between 5 percent and 10 percent. At high idle, the duty cycle should be between 90 percent and 95 percent.Results:
OK - The throttle command is correct. The ECM is not processing the command properly. Verify that the ECM is receiving the correct battery voltage. If the ECM is receiving the correct battery voltage, replace the ECM.Repair: Refer to Troubleshooting, "Replacing The ECM" before replacing the ECM. Stop.
Not OK - The throttle command is not correct. There is a problem in the harness or connectors between the Machine Control Module and the ECM. Repair the circuit. Verify that the repair eliminates the problem. Stop.