BREATHER AS 9U8119 - Caterpillar

System Operation Description:Use this procedure in order to troubleshoot the Engine Control Switch (ECS) or use this procedure if the diagnostic code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
336-2 Incorrect ECS Switch inputs The two inputs from the ECS are in the opposite state. The code is logged. The Electronic Control Module (ECM) receives four input signals from the ECS. The input signals allow the control to determine the mode of operation. The ECS can operate in four modes: OFF, MAN/START, COOLDOWN/STOP and AUTO.When the ECS is set to the OFF position, the start/run/stop inputs to the ECM and the auto input to the ECM is open. The ECM is not powered. Engine operation will stop when the ECS is switched to this position.When the ECS is set to the AUTO position, the start/run/stop inputs to the ECM are open and the auto input to the ECM is low. The ECM is powered. If the remote start switch is closed, the engine start sequence will begin.When the ECS is set to the MAN/START position, the start/run/stop inputs to the ECM are low and the ECS in auto input to the ECM is open. The ECM will begin the engine start sequence.When the ECS is set to the COOLDOWN/STOP position, the start/run/stop inputs to the ECM are open and the ECS in auto input is open. After the engine cooldown, the ECM will shut down the engine.If the inputs from the start/run/stop input to the ECM are in opposite states, the ECM determines that one of the inputs is faulty. The ECM will not initiate the engine start sequence. The ECM generates a diagnostic code. The diagnostic code will be active until the condition is corrected. If this occurs, the engine may be cranked manually. Use the "Manual Crank Switch" which is located inside the electronic instrument panel. When the engine is shutdown, the ECS must be placed in the OFF position. This will disconnect power to the input for the keyswitch on the ECM and the ECM will power down. The status for the ECS will display "ABNORMAL DATA" until the condition is corrected.If the engine is running and the inputs from the start/run/stop input to the ECM change to opposite states, the engine will continue to run. The ECM generates a diagnostic code. The condition must be corrected before the ECM will initiate another engine start sequence.If you close the remote start switch, and the ECS is in the AUTO position, the engine will start. The status for the switch will display "ON" or "OFF". This status of the remote start switch is available on the Caterpillar Electronic Technician (ET) when the ECS is in the AUTO position.
Illustration 1 g01218372
Typical schematic
Illustration 2 g01218373
P1 ECM connector
(P1-5) Digital return
(P1-21) "Start/Run/Stop 1"
(P1-22) "Start/Run/Stop 2"
(P1-68) "ECS in Auto"
Illustration 3 g01234146
Location of ECM connectors
Illustration 4 g01218374
"Connector A"
(Terminal 18) "ECS in Auto"
(Terminal 25) Digital return
Illustration 5 g01218376
"Connector B"
(Terminal 2) "Start/Run/Stop 1"
(Terminal 3) "Start/Run/Stop 2"
Illustration 6 g01218377
Customer connector
(Terminal 20)