3500B Marine Engines Caterpillar

Synchronizing Switch Not Functioning Properly

Usage:

Note: For details regarding the wiring harness, refer to the Electrical Schematic for the Engine.

The probable root causes are listed below:

Vessel wiring
Faulty switch
Electronic Control Module (ECM)
Faulty display indicator

Show/hide table




Illustration 1	g00774907
Dual Engine

Check the wiring for the following problems: damage, abrasion, corrosion and incorrect attachments.

Check the harness resistance from the ECM to the − Battery terminal.
Turn the Engine Control Switch (ECS) to the "OFF" position. Disconnect the ECM connector P1 from the primary ECM and P1 from the secondary ECM.
1. Put the synchronizing switch to the "Sync PORT" position.
2. Measure the resistance from the primary ECM P1-19 to the − Battery terminal. The resistance should be less than 10 Ohms.
3. Measure the resistance from the secondary ECM P1-19 to the − Battery terminal. The resistance should be less than 10 Ohms.
4. Measure the resistance from the primary ECM P1-13 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
5. Measure the resistance from the secondary ECM P1-13 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
6. Put the synchronizing switch to the "Sync Starboard" position.
7. Measure the resistance from the primary ECM P1-19 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
8. Measure the resistance from the secondary ECM P1-19 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
9. Measure the resistance from the primary ECM P1-13 to the − Battery terminal. The resistance should be less than 10 Ohms.
10. Measure the resistance from the secondary ECM P1-13 to the − Battery terminal. The resistance should be less than 10 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
11. If the resistance measurements are correct, temporarily replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM. If the resistance measurements are incorrect, proceed to Test Step 3.
Check the harness resistance between the 40-pin connector (port side) and the ECM.
1. Put the synchronizing switch to the "Sync PORT" position.
2. Disconnect the 40-pin connector (port side). Make a wire jumper that will extend from the 40-pin connector to the − Battery terminal.
3. Connect one end of the wire jumper to the − Battery terminal. Connect the other end of the wire jumper to J3-2 on the 40-pin connector (port side).
4. Measure the resistance from the primary ECM P1-19 to the − Battery terminal. The resistance should be less than 10 Ohms.
5. Measure the resistance from the secondary ECM P1-19 to the − Battery terminal. The resistance should be less than 10 Ohms.
6. Measure the resistance from the primary ECM P1-13 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
7. Measure the resistance from the secondary ECM P1-13 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
8. Put the synchronizing switch to the "Sync Starboard" position.
9. Remove the wire jumper from J3-2 of the 40-pin connector (port side). Connect the wire jumper to J3-1 of the 40-pin connector (port side).
10. Measure the resistance from the primary ECM P1-19 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
11. Measure the resistance from the secondary ECM P1-19 to the − Battery terminal. The resistance should be greater than 20,000 Ohms.
12. Measure the resistance from the primary ECM P1-13 to the − Battery terminal. The resistance should be less than 10 Ohms.
13. Measure the resistance from the secondary ECM P1-13 to the − Battery terminal. The resistance should be less than 10 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
14. If the resistance is within the range, proceed to Test Step 4. If the resistance is incorrect, repair the harness between the 40-pin connector (port side) and the ECM.
Check the Throttle Synchronization Switch for continuity.
1. Put the synchronizing switch to the "Sync PORT" position.
2. Measure the resistance between pin-3 and pin-4 on the synchronizing switch. The resistance should be less than 10 Ohms.
3. Measure the resistance between pin-3 on the synchronizing switch and the − Battery terminal. The resistance should be less than 10 Ohms.
4. Measure the resistance between pin-2 on the synchronizing switch and P3-2 on the 40-pin connector (port side). The resistance should be less than 10 Ohms.
5. Measure the resistance between pin-5 on the synchronizing switch and P3-1 on the 40-pin connector (port side). The resistance should be less than 10 Ohms.
6. Put the synchronizing switch in the "Sync PORT" position. Measure the resistance between pin-3 and pin-2 on the synchronizing switch. The resistance should be less than 10 Ohms.
7. Measure the resistance between pin-5 and pin-4 on the synchronizing switch. The resistance should be greater than 20,000 Ohms.
8. Put the synchronizing switch in the "Sync Starboard" position. Measure the resistance between pin-3 and pin-2 on the synchronizing switch. The resistance should be greater than 20,000 Ohms.
9. Measure the resistance between pin-5 and pin-4 on the synchronizing switch. The resistance should be less than 10 Ohms.
10. If the resistance measurements are incorrect, repair the harness and/or the synchronizing switch. If the resistance is within the range, proceed to Test Step 5.
Check the harness resistance between the 25-pin engine connector P3B and the ECM.
1. Disconnect the 25-pin engine connector "P3B". Make a wire jumper that will extend from the 25-pin engine connector "P3B" to the − Battery terminal. Connect one end of the wire jumper on the − Battery terminal. Connect the other end of the wire jumper on P3B-8 of the 25-pin engine connector "P3B".
2. Measure the resistance between the primary ECM P1-19 and the − Battery terminal. The resistance should be less than 10 Ohms.
3. Measure the resistance between the secondary ECM P1-19 and the − Battery terminal. The resistance should be less than 10 Ohms.
4. Measure the resistance between the primary ECM P1-13 and the − Battery terminal. The resistance should be greater than 20,000 Ohms.
5. Measure the resistance between the secondary ECM P1-13 and the − Battery terminal. The resistance should be greater than 20,000 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
6. Remove the wire jumper from P3B-8 of the 25-pin engine connector "B". Insert the jumper onto P3B-10 of the 25-pin engine connector "B".
7. Measure the resistance between the primary ECM P1-19 and the − Battery terminal. The resistance should be greater than 20,000 Ohms.
8. Measure the resistance from the secondary ECM P1-19 and the − Battery terminal. The resistance should be greater than 20,000 Ohms.
9. Measure the resistance from the primary ECM P1-13 and the − Battery terminal. The resistance should be less than 10 Ohms.
10. Measure the resistance between the secondary ECM P1-13 and the − Battery terminal. The resistance should be less than 10 Ohms.
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
11. If the resistance is within the range, proceed to Test Step 6. If the resistance is incorrect, repair the wiring between the 25-pin engine connector "P3B" and the ECM.
Check the resistance of the harness between the 25-pin engine connector and the 40-pin connector (port side).
1. Turn the ECS to the "OFF" position. Disconnect the 25-pin engine connector. Disconnect the 40-pin connector (port side).
2. Measure the following resistances between the 25-pin engine connector and the 40-pin connector (port side):
  - J3B-10 to J3-7
  - J3B-8 to J3-2
  Note: Wiggle the harness during the measurements in order to reveal an intermittent condition.
  The resistance should be less than 10 Ohms through the harness.
3. If the resistance is greater than 10 Ohms, then there is an open circuit in the harness. Repair the harness or replace the harness.