0281869 JOHNSON DECAL SET, 90

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 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 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 one second. The voltage returns above 9 VDC.
or
Three voltage readings in the last seven seconds were below 9 VDC.
1834-2 Ignition Keyswitch loss of signal The ECM detects at least three changes to the state of the signal that is for the keyswitch in the last one second. The code is logged. The electrical power supply for the engine ECM and the other engine controllers consists of several components. A low current power distribution panel is used to accommodate the circuit protection for low current devices. Circuit protection for the low current power distribution panel is provided by a main circuit breaker that is located in the high current power distribution panel.
Illustration 1 g01291985
Location of the high current power distribution panel (rear left side engine view)
(1) Starter relays
(2) Circuit breakers
(3) Battery disconnect switch Starter relays (1), circuit breakers that are greater than 25 amp (2), and the battery disconnect switch (3) are accommodated in this panel. The circuit breakers that are found in this panel include the engine's main circuit breaker, the starting motor's circuit breaker, the alternator's circuit breaker, and the prelubrication motor's circuit breaker. The high current power distribution panel provides the connection terminals for a direct connection to the engine's batteries.
Illustration 2 g01530500
Location of the low current power distribution panel (front left side engine view)
(4) Harness for the low current power distribution panel
(5) Low current power distribution panel The low current power distribution panel (4) is connected to the control box through harness (5).
Illustration 3 g01530502
Location of the connectors at low current power distribution panel (7) that are for the engine's electrical power supply
(6) Fuse for the temperature control module
(7) Gray connector
(8) ECM relay
(9) Fuse for the service tool connector and for the relays that are for the starting system's manual override
(10) Yellow connector
(11) Orange connector
(12) Fuse for the ECM
(13) Blue connector
(14) Fuse for the exhaust temperature module
(15) Fuse for the keyswitch circuit
(16) −Battery
(17) +Battery
(18) Fuse for the fuel control valve's controller The following circuits for this application are fused at the low current power distribution panel:
ECM
Fuel control valve's controller
Keyswitch
Aux 1 (power to the EMCP 3 through the engine interface connector)
Exhaust temperature module
Relays for the starting system's manual override
Temperature control modulePower for the engine ECM is provided through the ECM relay. The ECM relay is used to provide electrical power to the ECM and various controllers. The control circuit for the relay (normally open contact) is wired from the ECM relay through the emergency stop switch (normally open switch) to battery power. The secondary circuit for the relay is power directly from battery power through a fuse that is located in the low current power distribution panel. This circuit is also protected by the main breaker at the high current power distribution panel.The ECM performs the task of stopping the engine in the case of an emergency stop shutdown. There are two emergency stop circuits that are associated with the ECM. For this application, the wires from these ECM inputs create a redundant circuit that is spliced together in the interconnect harness between the engine interface connector and the generator set control panel. The circuit in the interconnect harness continues to the emergency stop switch. Beyond the switch, the circuit is wired to a digital return at the ECM. As the switch contacts of the emergency stop switch are closed, the switch inputs at the ECM are grounded through the switch. The ECM discontinues power to the injector solenoids and the engine is shut down.Power for the keyswitch circuit is provided through the keyswitch relay. The control circuit for this relay is continuously powered. The secondary circuit for the relay is power directly from battery power through a fuse that is located in the low current power distribution panel. This circuit is also protected by the main breaker at the high current power distribution panel. The keyswitch circuit also powers the temperature control module and the fuel control valve's controller.The engine's power mode circuit allows the ECM to control the power to various components. This application utilizes the power mode circuit to power the exhaust temperature module. The control circuit for the relay that is for the power mode circuit is powered by a high side ECM driver. The secondary circuit for the relay is powered by the output of the ECM relay. The ECM relay must be providing power to the ECM in order for the power mode circuit to be powered.
Illustration 4 g01818213
Schematic for the electrical power supply
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the battery disconnect switch to the OFF position.
Illustration 5 g01820516
Location of the connectors at the control box that are for the electrical power supply (typical top front engine view)
(19) J1/P1 ECM connector
(20) J2/P2 ECM connector
(21) Engine interface connector at the control box
(22) Relay for the keyswitch circuit
(23) Relay for the power mode circuit
(24) Connector to the low current power distribution panel
Thoroughly inspect connectors (19), (20), (21), and (24). Also, thoroughly inspect the connectors for relays (22) and (23). Inspect the wiring for the crossover harness that is in the control box for abrasion. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the proper procedure for inspecting system wiring.