850046A 2 Mercury HARNESS-IGNITION

Illustration 1 g01071348
Top view
(1) Inlets for the turbocharger compressors
(2) Turbocharger compressor bypass valves
(3) Outlet of the aftercooler Two turbocharger compressor bypass valves (2) are connected between the outlet of the aftercooler (3) and the inlets for the turbocharger compressors (1). Each valve is activated by a solenoid. Some engines are configured with one turbocharger compressor bypass valve. This troubleshooting procedure applies to both configurations.When the valves are activated, pressurized air from the aftercooler flows into the intake of the engine. This reduces the boost pressure in the air inlet manifold.The ECM activates the solenoids for the valves during these conditions:
Turbocharger surge
Engine shutdownTurbocharger Surge - A rapid drop in the output power of the generator can cause the engine's speed to quickly increase. The increased speed of the engine causes the turbochargers to overspeed temporarily. This is called a turbocharger surge. Surging can damage the turbochargers.The generator's switchgear contains a generator output power sensor. This sensor produces a low voltage signal that indicates the amount of power that is being produced by the generator. The sensor's signal is sent to the ECM. The ECM continuously monitors the signal from the sensor. The ECM responds to a rapid drop in the signal from the sensor by activating the solenoids. The solenoids open the valves.The valves allow the compressed air/fuel mixture in the aftercooler to flow into the intake of the turbocharger's compressor. This reduces the pressure that is created by the turbocharger's compressor.Engine ShutdownEngine shutdown occurs when the output for the fuel control relay is OFF and the engine rpm is above 100. The ECM activates the output for the solenoids until the engine rpm drops to zero. This scavenges any unburned gases in the components of the system during engine shutdown.A "Turbocharger Compressor Bypass Valve Solenoid" diagnostic code is probably caused by a problem with an electrical connector or a harness. The next likely cause is a problem with a solenoid. The least likely cause is a problem with the ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.This procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the logged codes after the problem is resolved.
Illustration 2 g01071347
Schematic for the compressor bypass valves
Test Step 1. Inspect the Electrical Connectors and Wiring
Illustration 3 g01076938
(4) Ground strap
(5) J2/P2 connectors for the ECM
(6) J1/P1 connectors for the ECM
(7) 16 amp circuit breaker
(8) J10/P10 connector for the harness from the solenoids
Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (7) to the OFF position. Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Thoroughly inspect the following connectors:
J1/P1 and J2/P2 connectors
J10/P10 connectors on the terminal box
Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 1 N m (55 9 lb in).
Illustration 4 g01071377
Harness side of the P2 connector
(P2-6) High side wire for the solenoids
(P2-7) Low side wire for the solenoids
Illustration 5 g00906760
Harness side of the P10 connector
(P10-A) High side wire for the solenoids
(P10-B) Low side wire for the solenoids
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the solenoids.
Illustration 6 g01071383
Right side view
(8) Solenoid
(9) Connector
(10) Valve
Thoroughly inspect connectors (9) for solenoids (8). Verify that the connectors do not have moisture or contamination. Check the harness and wiring for abrasion and for pinch points from each solenoid to the ECM. Expected Result:The connectors and terminals are connected properly. The connectors are free of moisture and of corrosion. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - The components are in good condition with proper connections. Proceed to Test Step 2.
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 the Low Side Wire for a Short to the +Battery
Disconnect the connectors for both of the solenoids for the turbocharger compressor bypass valves.
Disconnect the P1 and P2 connectors.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Illustration 7 g01071398
Terminal box
(4) Ground strap
(P2-7) Low side wire for the solenoids
Measure the voltage between terminal P2-7 and ground strap (4). Expected Result:The voltage is approximately zero volts.Results:
OK - The voltage at terminal P2-7 is approximately zero volts. The low side wire does not have a short circuit to the +Battery. Proceed to Test Step 3.
Not OK - The voltage at terminal P2-7 is approximately equal to the +Battery voltage. The low side wire has a short circuit to the +Battery. The short circuit could be inside the terminal box or in the engine harness.Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.STOPTest Step 3. Check the Low Side Wire for a Short to Ground
Switch the 16 amp circuit breaker OFF. Set the engine control to the OFF/RESET mode.