824003A 9 Mercury ECU, Engine Control Unit

Illustration 1 g01325630
Schematic of the 4 to 20 mA desired speed input
Test Step 1. Inspect the Electrical Connectors and Wiring
Remove the electrical power from the engine. Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".
Thoroughly inspect the following components:
J1/P1 connectors
J6/P6 connectors
Wiring and the connections between the terminal box and the device that supplies the 4 to 20 mA signal
Check the torque of the allen head screw for the ECM connectors.
Check the harness and wiring for abrasion and for pinch points between the device that supplies the 4 to 20 mA signal and the ECM. Expected Result:All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - The components are in good condition with proper connections. If you are troubleshooting a 524-3 diagnostic code, proceed to Test Step 2. If you are troubleshooting a 524-4 diagnostic code, proceed to Test Step 5.
Not OK - The components are not in good condition and/or at least one connection is improper.Repair: Perform the necessary repairs and/or replace parts, if necessary.STOPTest Step 2. Check for an Open Circuit
Remove the two wires (+ and −) for the 4 to 20 mA signal from the device that supplies the 4 to 20 mA signal.
Install a jumper wire between the two wires (+ and −) that were removed from the device that supplies the 4 to 20 mA signal.
Disconnect the P1 connector from the ECM.
Measure the resistance between terminals P1-36 and P1-37 on the ECM side of the P1 connector. Expected Result:The resistance is less than 5 Ohms.Results:
OK - The resistance is less than 5 Ohms. The circuit is not open.Repair: Remove the jumper wire. Insulate the wire leads with electrical tape in order to ensure that the leads do not create a short circuit.Proceed to Test Step 3.
Not OK - The resistance is greater than 5 Ohms. There is a problem with a connector and/or the wiring from the P1 connector.Repair: The problem may be between the P1 connector and the J6 connector. Alternatively, the problem may be between the J6 connector and the device that provides the 4 to 20 mA signal.Repair the connection and/or the wire, when possible. Replace parts, if necessary. Verify that the problem is resolved.STOPTest Step 3. Check for a Short Circuit to the +Battery at Terminal P1-36
Verify that the electrical power is removed from the engine.
Make sure that there is no electrical power to the device that provides the 4 to 20 mA signal.
Measure the resistance between terminals P1-36 and P1-57 on the ECM side of the P1 connector. Expected Result:The resistance is