0388271 JOHNSON BODY ASSEMBLY

Illustration 1 g00914991
Top view of the engine (1) Inlets for the turbocharger compressors (2) Turbocharger compressor bypass valves (3) Outlet of the aftercoolerTwo 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.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 master ECM activates the solenoids for the valves during these conditions:
Turbocharger surge
Engine shutdownA rapid reduction in the generator's power output can cause the engine's speed to rapidly increase. The increased engine speed causes the turbochargers to produce boost pressures that are greater than the requirement for engine operation. 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 master ECM. The master ECM continuously monitors the signal from the sensor. The master 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 compressor. This reduces the pressure that is created by the compressor.Engine shutdown occurs when the output for the fuel control relay is OFF and the engine RPM is above 100. The master 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 master 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 g00993419
Schematic of the circuit for the solenoidsTest Step 1. Inspect the Electrical Connectors and Wiring
Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Illustration 3 g00995487
(1) Ground strap (2) J2/P2 connectors for the master ECM (3) J1/P1 connectors for the master ECM (4) J10/P10 connector for the harness from the solenoids (5) 16 amp circuit breaker
Thoroughly inspect the following connectors:
Master ECM 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 g00995488
Harness side of the ECM 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 g00907698
Side view of a turbocharger compressor bypass valve (6) Solenoid (7) Connector (8) Valve
Thoroughly inspect connectors (7) for solenoids (6). Verify that connectors (7) do not have moisture or contamination. Check the harness and wiring for abrasion and for pinch points from each solenoid to the master 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.
Disconnect the P1 and P2 connectors.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Illustration 7 g00906771
(1) Ground strap (P2-7) Low side wire for the solenoids
Measure the voltage between terminal P2-7 and ground strap (1) for the ECM.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 side. 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 side. 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 the harness, 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.