COVER 1W5785 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's Electronic Control Module (ECM) 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
168-0 Electrical System Voltage high - most severe (3) The battery supply voltage is greater than 32 VDC for two seconds.
The engine's ECM has been powered for three seconds.
The engine is not being cranked. The code is logged.
168-1 Electrical System Voltage low - most severe (3) The battery supply voltage is less than 9 VDC for two seconds.
The engine's ECM has been powered for three seconds.
The engine is not being cranked.
168-2 Electrical System Voltage erratic, intermittent, or incorrect The engine is running. The battery voltage falls below 9 VDC for at least .06 seconds. The voltage returns above 9 VDC.
or
Three voltage readings in the last seven seconds were below 9 VDC. The engine's ECM receives 24 VDC from the battery. Electrical power comes from the 20 amp breaker for the ECM to the normally close contacts of relay "R2A". The electrical power to the ECM from the normally closed contact of relay "R2A" is on wire C150 and on wire 150. The wire C150 goes to pin P1-53 of ECM connector J1/P1. The wire 150 goes to pin P1- 52 of ECM connector J1/P1. The −Battery is applied to pin P1-63 and pin P1-65 of ECM connector J1/P1. The wire numbers for the −Battery are wire D229 and wire 229 . The Engine Control Switch (ECS) sends a signal to pin P1-70 of the ECM when the ECS is in the following positions: REMOTE, STOP and START. When the ECM senses battery voltage on pin P1-70 of the ECM, the ECM will power up. When the ECS is in the OFF/RESET position, voltage is not present on P1-70 and the ECM will power down.When the emergency stop switch is activated, relays"R4" and "R4A" energize. Electrical power from relay "R4A" is routed to terminal 3 of the timer. When 24 VDC is applied to terminal 3 of the timer, the timer activates for 2.5 seconds. The timer outputs 24 VDC to the coil of the air shutoff switch (ASOS). The timer also outputs 24 VDC to the diode assembly and to the coils of relay "R3A" and relay "R3". When relay "R3A" is energized, power is applied to the coil of relay "R2A". When relay "R2A" is energized, the normally closed contacts of relay "R2A" open. This removes electrical power to the ECM.In order to restart the engine, the operator must correct the cause of the emergency stop condition. The ECS must be turned to the OFF/RESET position for three seconds. This resets the ECM and the air shutoff timer. In addition to turning the ECS to the OFF/RESET position, the operator must manually open the air shutoff valves before starting the engine.The presence of two +Battery connections and