856101 Volvo.Penta Idle screw

Illustration 1 g00794033
SchematicTest Step 1. Check for Connector Damage
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect the J1/P1 ECM connector, the J3/P3 machine connector, the J24/P24 ground level shutdown switch connector, any other connectors, and the wiring in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.Expected Result:The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.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 Switch Status on ET
Install ET to the service tool connector.
Turn the keyswitch to the ON position.
Observe the status for "Shutdown Switch" on ET while you operate the ground level shutdown switch.
Turn the keyswitch to the OFF/RESET position.Expected Result:The status should be "On" with the switch in the STOP position. The status should be "Off" with the switch in the RUN position.Results:
OK - The switch is operating normally.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent. Stop.
Not OK - Proceed to Test Step 3.Test Step 3. Short the Wires at the Switch
Disconnect the J24/P24 ground level shutdown switch connector.
Install a jumper wire between P24:B (Ground Level Shutdown (NC)) and P24:C (Digital Sensor Return).
Turn the keyswitch to the ON position and observe the status for "Shutdown Switch" on ET.The status should be "Off".
Remove the jumper wire.
Install the jumper wire between P24:A (Ground Level Shutdown (NO)) and P24:C (Digital Sensor Return).
Ensure that the keyswitch is in the ON position and observe the status for "Shutdown Switch" on ET.The status should be "On".
Remove the jumper wire.Expected Result:The status should be "Off" with the jumper wire between P24:B (Ground Level Shutdown (NC)) and P24:C (Digital Sensor Return). The status should change to "On" when you move the jumper wire to P24:A (Ground Level Shutdown (NO)) and P24:C (Digital Sensor Return).Results:
OK - There is a problem with the switch.Repair: Temporarily connect a new switch. Verify that the new switch solves the problem before you permanently install the new switch. Stop.
Not OK - There is a problem in the harness and/or the ECM. Proceed to Test Step 4.Test Step 4. Check for a Short Circuit in the Wiring Harness
Illustration 2 g00794059
P1 ECM connector
Turn the keyswitch to the OFF/RESET position.
Disconnect the J1/P1 ECM connector. The J24/P24 ground level shutdown switch connector should already be disconnected.
Measure the resistance between the following terminals:
P1:25 (Ground Level Shutdown (NO)) to P1:29 (Digital Sensor Return)
P1:24 (Ground Level Shutdown (NC)) to P1:29 (Digital Sensor Return)
P1:25 (Ground Level Shutdown (NO)) to P1:24 (Ground Level Shutdown (NC))
P1:24 (Ground Level Shutdown (NC)) to engine ground
P1:25 (Ground Level Shutdown (NO)) to engine groundExpected Result:The resistance should be greater than 20,000 Ohms for each measurement.Results:
OK - There are no shorts in the harness. Proceed to Test Step 5.
Not OK - There is a short circuit in the harness or connectors between the switch and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 5. Check the Resistance Through the Harness
Illustration 3 g00794059
P1 ECM connector
Ensure that the J1/P1 ECM connector and the J24/P24 ground level shutdown switch connector are disconnected.
Install a jumper wire between P24:A (Ground Level Shutdown Switch (NO)) and P24:C (Digital Sensor Return).
Measure the resistance between P1:25 (Ground Level Shutdown (NO)) and P1:29 (Digital Sensor Return).
Remove the jumper wire.
Install the jumper wire between P24:B (Ground Level Shutdown Switch (NC)) and P24:C (Digital Sensor Return).
Measure the resistance between P1:24 (Ground Level Shutdown (NC)) and P1:29 (Digital Sensor Return).
Remove the jumper wire.Expected Result:The resistance should be less than 10 Ohms for each measurement.Results:
OK - The resistance is within acceptable limits. Proceed to Test Step 6.
Not OK - There is an open circuit or excessive resistance in the harness.Repair: Repair the harness.Verify that the repair eliminates the problem. Stop.Test Step 6. Short the Switch Inputs at the ECM
Illustration 4 g00794059
J1/P1 breakout
Turn the keyswitch to the OFF/RESET position.
Ensure that the J24/P24 ground level shutdown switch connector is disconnected.
Install a 7X-1715 Adapter Cable (40 Pin Breakout) at the J1/P1 ECM connector.
Install the jumper wire between P1:24 (Ground Level Shutdown (NC)) and P1:29 (Digital Sensor Return) at the breakout.
Turn the keyswitch to the ON position and observe the status for "Shutdown Switch" on ET.The status should be "Off".
Remove the jumper wire from the breakout.
Install the jumper wire between P1:25 (Ground Level Shutdown (NO)) and P1:29 (Digital Sensor Return) at the breakout.
Observe the status for "Shutdown Switch" on ET.The status should be "On".
Turn the keyswitch to the OFF/RESET position.Expected Result:The status should be "Off" with the jumper wire between P1:24 (Ground Level Shutdown (NC)) and P1:29 (Digital Sensor Return). The status should change to "On" when you move the jumper wire to P1:25 (Ground Level Shutdown (NO)) and P1:29 (Digital Sensor Return).Results:
OK - The ECM properly reads the switch inputs at the ECM connector P1 but not at the switch.Repair: The wiring harness is faulty. Repair the wiring harness. Verify that the repair eliminates the problem. Stop.
Not OK - The ECM is not reading the switch inputs properly.Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM