44354A13 Mercruiser ELBOW ASSEMBLY, Exhaust

Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
446-5 Air Shutoff Relay current below normal The Electronic Control Module (ECM) detects an open circuit and/or a short to the +Battery in the circuit for the air shutoff switch ("ASOS"). The ECM can only detect this condition when the "ASOS" is not energized. The code is logged.
446-6 Air Shutoff Relay short The ECM detects a short circuit to ground in the "ASOS" circuit. The ECM can only detect this condition when the "ASOS" is energized. The ECM has the ability to stop the engine by shutting off the inlet air supply in an emergency situation. The ECM activates the output driver for the emergency shutdown system. The "ASOS" energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves.There are two conditions which cause the engine control to activate the output driver for the air shutoff switch. The first condition occurs when the operator activates the customer's emergency stop. When the customer's emergency stop button is activated, the emergency stop inputs U and T to the ECM from the customer connector go high. The ECM will recognize this change. The ECM will energize the output drive for the emergency shutdown system for one second through the diode assembly.The second condition occurs for an engine overspeed. If an engine overspeed occurs, the ECM will activate the "ASOS" for the emergency shutdown system through the diode assembly.Relay "R3A" and relay "R3" are energized at the same time as the "ASOS" through terminal 3 of the diode assembly. Terminal 3 of the diode assembly will energize relay "R3A" and relay "R3" for one second. The contacts of relay "R3" keeps relay "R3A" and relay "R3" energized until power is cycled. The contact of relay "R3A" keeps the coil of relay "R2A" energized. When relay "R2A" is energized, power is removed from the ECM. The ECM will power down. The injection signals to the injector solenoids will stop.The contact of relay "R3A" also supplies power to terminal 3 of the connector for a timer and to the overspeed indicator on the instrument panel. When power is applied to terminal 3 of the connector for the timer, the timer will activate. The timer outputs 24 VDC from terminal 6 of the connector for the timer for 2.5 seconds. The 24 VDC from the timer is applied to the coil of the "ASOS" and to terminal 2 of the diode assembly. The "ASOS" energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves. The 2.5 second time limit for activation of the "ASOS" prevents damage to the air shutoff solenoids. A normally closed switch at the air shutoff valves will open when the air shutoff solenoid activates the air shutoff valve. The switch input to the ECM notifies the ECM that the air shutoff valves are closed. The ECM will not send injection signals to the injector solenoids until the switch inputs from the air shutoff valves indicate that the valves are open. An overspeed can be simulated by using the Caterpillar Electronic Technician (ET). In order to verify that the overspeed function is operable, the operator must access the screen for overriding parameters on Cat ET. When the override for the engine overspeed is set to the ON position, the setpoint for the engine overspeed is at 75 percent of the original setpoint. When the engine reaches the modified setpoint, the normal strategy for an engine overspeed is initiated.The engine is equipped with a redundant overspeed circuit. The circuit consists of a magnetic pickup that sends a pulsed signal to a speed switch. When an overspeed condition occurs, the speed switch detects the overspeed by monitoring the signal from the magnetic pickup. The speed switch will close a set of normally open contacts. The contacts will energize relay "R3A" and relay "R3". The overspeed indicator light on the instrument panel will illuminate. The contacts of relay "R3" keeps relay "R3A" and relay "R3" energized until power is cycled. The contact of relay "R3A" keeps the coil of relay "R2A" energized. When relay "R2A" is energized, power is removed from the ECM. The ECM will power down. The injection signals to the injector solenoids will stop.The "ASOS" can be activated independently of the sourcing driver of the ECM. When the local emergency stop switch on the instrument panel is depressed or the remote emergency stop switch is activated, the coils of relay "R4" and relay "R4A" are energized. The contacts of relay "R4A" supplies power to terminal 3 of the connector for the timer and to the coil of relay "R2A". When relay "R2A" is energized, power is removed from the ECM. The circuit will operate in the same manner that was described above except that the emergency stop lamp on the instrument panel will illuminate and the relays "R3A" and "R3" will de-energize after 2.5 seconds. When relays "R3A" and "R3" de-energize, the overspeed indicator turns off.Regardless of the reason for activation, the Engine Control Switch (ECS) must be turned to the OFF/RESET position for three seconds. This resets the ECM and the relays in the circuit. In addition to turning the ECS to the OFF/RESET position, the operator must determine the cause for the emergency shutdown before resetting the circuit. The operator must manually open the air shutoff valves before restarting the engine.
Illustration 1 g01243460
Typical schematic
Illustration 2 g01234146
Location of ECM connectors
Illustration 3 g01240839
Connector P-C1 of the power distribution panel
(Terminal G) Drive to "ASOS"
(Terminal I) Drive to air shutoff solenoid Test Step 1. Inspect Electrical Connectors and Wiring
Verify that the circuit breakers are not tripped.
Turn the circuit breaker for the battery to the OFF position.
Turn the ECS to the OFF/RESET position.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors that are related to the circuit. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are