SPRING 3G9609 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the air shutoff system or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
446-5 Air Shutoff Relay open The Electronic Control Module (ECM) detects an open circuit and/or a short to the +Battery in the solenoid circuit. The ECM can only detect this condition when the air shutoff solenoid is not energized. The code is logged.
446-6 Air Shutoff Relay short The ECM detects a short circuit to ground in the solenoid circuit. The ECM can only detect this condition when the air shutoff solenoid is not energized. The ECM has the ability to stop the engine by shutting off the air supply in an emergency situation. The ECM activates the air shutoff solenoid which activates the air inlet shutoff valve.The first condition occurs when the operator initiates an emergency shutdown. When the shutdown is recognized, fuel is shut off and the air shutoff solenoid is activated. The second condition is for an engine overspeed.The customer can activate the air shutoff solenoid by supplying 24 VDC to terminal 04 of the customer connector.Regardless of the reason for activation, the main power to the ECM must be turned OFF for three seconds in order to reset the engine control.Note: The air shutoff is optional. A programmable parameter needs to be set with Caterpillar Electronic Technician (ET) in order to enable the air shutoff.Note: Ensure that the air shutoffs are manually reset after an emergency stop in order to start the engine again.
Illustration 1 g01227331
Typical schematic for the air shutoff system
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Illustration 2 g01227322
Location of the components for the air shutoff system (typical left side engine view)
(1) Air shutoff solenoids
(2) Customer connector
(3) J1/P1 ECM connector
(4) J2/P2 ECM connector
Thoroughly inspect the connections at solenoids (1). Also, thoroughly inspect connectors (2), (3), and (4). Inspect all of the connectors that are associated with the circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Illustration 3 g01227424
P1 ECM connector
(P1-5) Digital return
(P1-21) Start/Run/Stop input 1
(P1-22) Start/Run/Stop input 2
(P1-23) Emergency stop signal "C"
(P1-28) Emergency stop signal "D"
(P1-52) +Battery
(P1-53) +Battery
(P1-55) +Battery (ECM)
(P1-56) Air shutoff (N/O)
(P1-63) −Battery
(P1-65) −Battery
(P1-70) Keyswitch
Illustration 4 g01227426
P2 ECM connector
(P2-13) Air shutoff
Illustration 5 g01227669
Customer connector
(Terminal 01) +Battery
(Terminal 02) +Battery
(Terminal 04) Air shutoff
(Terminal 09) Digital return
(Terminal 16) Emergency stop signal "D"
(Terminal 17) Emergency stop signal "C"
(Terminal 23) Start/Run/Stop input 1
(Terminal 24) Start/Run/Stop input 2
(Terminal 27) Keyswitch
(Terminal 34) −Battery
(Terminal 35) −Battery
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.
Check the