803537 Mercury COVER

Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
168-0 Electrical System Voltage : High The battery supply voltage is greater than 32 VDC for nine seconds.
The engines ECM has been powered for 30 seconds. The code is logged.
168-1 Electrical System Voltage : Low The battery supply voltage is less than 18 VDC for 0.5 seconds.
The engines ECM has been powered for three seconds.
The engine has started and the engine is running. The code is logged.
Engine parameters for most of the powered sensors will revert to default values.
168-2 Electrical System Voltage : Erratic, Intermittent, or Incorrect The engine is running.
Three voltage readings in the last seven seconds were below 6 VDC. The voltage then returned to above 9 VDC. The code is logged.
1834-2 Ignition Key Switch loss of signal Three voltage readings for the keyswitch for the last one second were below an acceptable voltage.
The engine is not cranking. The code is logged. Use this test if there are intermittent engine shutdowns or if a difficulty in starting is not accompanied by loss of electrical accessories. Engine shutdowns that are accompanied by a loss of other electrical accessories indicate a problem in the keyswitch. This does not indicate a problem in the wiring at the ECM. Verify that there are no problems with the starting system or with the charging system before you use this test.Unswitched battery voltage is supplied through the machine connector to the ECM. The voltage is supplied to terminals at P1-48, P1-52, P1-53, P1-55, and P1-57 of the ECM connector . The negative battery is supplied to the ECM at P1-61, P1-63, P1-65, P1-67, and P1-69. The ECM receives battery voltage from the keyswitch at P1-70 when the keyswitch is in the ON position or in the START position. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down. The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).
Illustration 1 g01622622
Typical schematic of the electrical power supply
Illustration 2 g01624112
Fuse that is in the cab of the machine
(1) 10 amp fuse that is for the keyswitch circuit
(2) 20 amp fuse that is for the ECM battery circuit
Illustration 3 g01619826
Locations of the connectors at the ECM that are for the 16 cylinder engines (typical left front engine view)
(3) J1/P1 ECM connectors
(4) Right rail connector
(5) Left rail connector
Illustration 4 g01619829
Locations of the connectors at the ECM that are for the 20 cylinder engines (typical left front engine view)
(3) J1/P1 ECM connectors
(4) Right rail connector
(5) Left rail connector
Illustration 5 g01619831
Location of the machine interface connectors (left rear engine view)
(6) Machine interface connectors
Illustration 6 g01854037
Location of the interface connector at the cab of the machine that is for the electrical power supply
(7) Interface connector at the cab of the machine
Illustration 7 g01323936
Terminal locations at the P1 ECM connector for the electrical power supply
(P1-48) +Battery
(P1-52) +Battery
(P1-53) +Battery
(P1-55) +Battery
(P1-57) +Battery
(P1-61) −Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-67) −Battery
(P1-69) −Battery
(P1-70) Keyswitch circuit
Illustration 8 g01446655
Terminal locations at the left rail connector that are for the electrical power supply
(Terminal 52) Keyswitch circuit
(Terminal 69) +Battery
(Terminal 70) +Battery
Illustration 9 g01446658
Terminal locations at the right rail connector that are for the electrical power supply
(Terminal 18) Keyswitch circuit