HOUSING 1261688 - 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 Engine Control Switch erratic, intermittent, or incorrect The two inputs from the ECS are in the opposite state. The code is logged. The ECS can operate in four modes: OFF/RESET, START, STOP and REMOTE.The engine's Electronic Control Module (ECM) receives three signals that allow the ECM to determine the mode of operation. The input signals on P1-21 and P1-22 tell the ECM the position of the ECS. The input signals on P1-21 and P1-22 must be at the same potential or a diagnostic code will be generated. The third input signal on P1-68 tells the ECM if the ECS is in the REMOTE position. If the input signal on P1-68 is low, the ECM knows that the ECS is in the REMOTE position. The ECM knows that the engine is controlled remotely by the customer. If the input signal on P1-68 is not low, the ECM knows that the ECS is not in the REMOTE position. The ECM knows that the engine is controlled locally by the ECS on the instrument panel.When the ECS is in the REMOTE position, inputs from the customer control the operation of the engine. The following list contains some of the inputs from the customer connector and the inputs function.
c keyswitch
S remote input
C remote start 2
D remote start 1
E remote stop 1
F remote stop 2When the ECS is in the REMOTE position, the "Remote Start" relay and the "Remote Stop" relay are energized. When the remote start inputs C and D go low, the following relays energize: "Run 1" relay, "Run 2" relay, "Reset 1" relay and "Reset 2" relay. The start/run/stop inputs P1-21 and P1-22 will be pulled low. The engine will begin the start cycle. When the customer's remote stop inputs F and E are low, the following relays energize: "Stop 1" relay and "Stop 2" relay. The start/run/stop inputs P1-21 and P1-22 will be high. The engine will begin the stop function. When the ECS is in the REMOTE position, the "ECS in Remote" relay energizes. The "ECS in Remote" relay sends a signal to the customer connector that allows the customer to determine the position of the ECS.When the ECS is in the START position, the following relays energize: "Run 1" relay, "Run 2" relay, "Reset 1" relay and "Reset 2" relay. The start/run/stop inputs P1-21 and P1-22 will be pulled low. The engine will begin the start cycle.When the ECS is in the STOP position, the following relays energize: "Stop 1" relay and "Stop 2" relay. The start/run/stop inputs P1-21 and P1-22 will be high. The engine will begin the stop function.When the ECS is in the OFF/RESET position, the input for the keyswitch P1-70 is not pulled up to +Battery voltage and the ECM will not operate.
Illustration