16416A87 Mercruiser DECAL, "420"

Illustration 1 g06540656
Schematic for the DCU electrical power supply circuit
Not all connectors are shown. Refer to the electrical schematic.
Table 2
Troubleshooting Procedure for the DCU Keyswitch Signal
Troubleshooting Test Steps Value Results
1. Inspect Electrical Connectors and Wiring
A. Turn the keyswitch to the OFF position.
B. Inspect the connectors in the circuit for the DEF control module.
Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the DEF control module power circuit.
D. Check the screw for the P1 ECM connector for correct torque of 6 N m (53 lb in).
E. Check all the wiring associated with the DEF Control module power circuit for abrasions and pinch points.
Damaged wire or connector
Result: A damaged wire or damaged connector was found.
Repair: Repair the damaged wire or the damaged connector.
Use the electronic service tool to clear all logged diagnostic codes.
Use the electronic service tool to perform the "Aftertreatment System Functional Test" to verify that the repair eliminates the fault.
Result: A damaged wire or damaged connector was not found.
Proceed to Test Step 2.
2. Determine the Code
A. Establish communication between the electronic service tool and the Electronic Control Module (ECM). Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Download the "Warranty Report" from the ECM before troubleshooting or clearing any diagnostic trouble codes.
C. Determine the diagnostic trouble code that is active.
Diagnostic Trouble Code
Result: A -5 diagnostic code is active.
Proceed to Test Step 3.
Result: A -6 diagnostic code is active.
Proceed to Test Step 5.
3. Create a Short Circuit at the 31 Pin Connector
A. Disconnect the 31-pin connector.
B. Fabricate a jumper wire. Install the jumper wire between terminal 4 on the 31-pin connector (ECM side) and a suitable ground.
C. Turn the keyswitch to the ON position.
D. Use the electronic service tool to check for active diagnostic codes.
Note: Other diagnostic codes will be active with the DCU connector disconnected. Disregard all other codes and only look for diagnostic codes that relate to the DCU keyswitch.
E. Turn the keyswitch to the OFF position.
Diagnostic codes
Result: A -6 diagnostic code is active with the jumper installed.
Proceed to Test Step 7.
Result: A -5 diagnostic code is active with the jumper installed.
Remove the jumper wire. Proceed to Test Step 4.
4. Check the Wiring for an Open Circuit
A. Disconnect the P1 connector from the ECM.
B. Measure the resistance between terminal 4 on the 31-pin connector (ECM side) and P1:2.
C. Measure the resistance between terminal 4 on the 31-pin connector (ECM side) and P1:3.
Less than 2 Ohms
Result: Both resistance measurements are less than 2 Ohms.
Contact the Dealer Solutions Network (DSN).
Result: At least one of the resistance measurements is greater than 2 Ohms.
Repair: Replace the wiring between the 31-pin connector and the ECM.
5. Create an Open Circuit at the 31 Pin Connector
A. Disconnect the 31-pin connector.
B. Remove the wire from terminal 4 of the 31-pin connector on the engine ECM side of the connector.
C. Reconnect the 31–pin connector.
D. Turn the keyswitch to the ON position.
E. Use the electronic service tool to check for active diagnostic codes.
F. Turn the keyswitch to the OFF position.
Diagnostic codes
Result: A -5 diagnostic code is active with the wire disconnected.
Reconnect the disconnected wire.
Proceed to Test Step 8.
Result: The -6 diagnostic code is still active with the wire disconnected.
Reconnect the disconnected wire.
Proceed to Test Step 6.
6. Check the Wiring for a Short Circuit
A. Disconnect the P1 connector from the ECM.
B. Measure the resistance between P1:2 and all other terminals on the P1 connector except P1:3.
C. Measure the resistance between P1:3 and all other terminals on the P1 connector apart from P1:2.
Greater than 1 K Ohms
Result: All resistance measurements are greater than 1 K Ohms.
Proceed to Test Step 7.
Result: At least one of the resistance measurements is less than 1 K Ohms.
Repair: Replace the wiring between the 31-pin connector and the ECM.
Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
7. Check the Wiring for a Short to Ground
A. Turn the keyswitch to the OFF position.
B. Disconnect the P1 connector from the ECM.
C. Measure the resistance between P1:2 and a known ground source.
D. Measure the resistance between P1:3 and a known ground source.
Greater than 1 K Ohms
Result: At least one of the resistance measurements is less than 1 K Ohms.
There is a short to ground in the wiring between the 31-pin connector and the ECM.
Repair: Replace the faulty wiring.
Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
Result: Both resistance measurements are greater than 1 K Ohms.
Proceed to Test Step 8.
8. Check if a Replacement PEU Eliminates the Fault
A. Make sure that the latest flash file for the application is installed in the DCU.
B. Contact the Dealer Solutions Network (DSN).
Note: This consultation can greatly reduce the repair time.
C. If the DSN recommends the use of a replacement PEU, install a replacement PEU.
D. Turn the keyswitch to the ON position. Use the electronic service tool to verify that the repair eliminates the fault.
Fault eliminated
Result: The fault is eliminated with the replacement PEU.
Repair: Reconnect the suspect PEU. If the fault returns with the suspect PEU, permanently install the replacement PEU.
Result: The fault is still present with the replacement PEU.
Do not use the replacement PEU. Contact the DSN.