0123975 JOHNSON COVER

Table 1
Diagnostic Trouble Codes for the Ignition Keyswitch and the Battery Supply Circuit
168-0 Battery Potential / Power Input #1 : High - most severe (3) The ECM detects the following conditions:
The battery supply voltage is greater than 16.5 VDC for at least 0.5 seconds.
The keyswitch has been ON for at least 2 seconds.
The warning lamp will flash and the shutdown lamp will come on.
The engine will shutdown and the engine will not restart as long as this condition exists.
The ECM is unable to control the fuel rack solenoid at this system voltage.
168-3 Battery Potential / Power Input 1 : Voltage Above Normal This code indicates that the battery circuit to the ECM has excessive voltage while the engine is running.
The ECM detects the following conditions:
The battery voltage is high for at least 0.5 seconds.
The engine has been running for at least 3 minutes.
The warning lamp will come on.
Active regeneration will be inhibited.
168-4 Battery Potential / Power Input 1 : Voltage Below Normal This code indicates that the battery circuit for the ECM has low voltage while the engine is running.
The ECM detects the following conditions:
The battery voltage is less than 6 VDC for at least 0.5 seconds.
The engine has been running for at least 3 minutes.
The warning lamp will come on.
The engine may experience changes in the engine rpm, intermittent engine shutdowns, or complete engine shutdowns while the code is present.
Active regeneration will be inhibited.
1485-7 ECM Main Relay : Not Responding Properly The ECM detects the following conditions:
The ECM detects battery voltage for at least 1 second after the main relay has been commanded off.
The keyswitch is in the OFF position.
The DPF outlet temperature is below 200° C (392° F).
The warning lamp will flash.
The ECM is receiving battery voltage after the keyswitch has been turned OFF, which will drain battery voltage.
1485-14 ECM Main Relay : Special Instruction The ECM requires battery voltage for up to 60 seconds after the keyswitch has been turned OFF.
A fault is caused when the ECM has lost battery voltage before this period has elapsed.
If equipped, the warning lamp will come ON.
This condition is most likely caused by shutting down the engine using the battery disconnect switch instead of the keyswitch for three consecutive shutdowns or using the battery disconnect switch immediately after the keyswitch has been turned OFF.
3484-3 Aftertreatment #1 Ignition : Voltage Above Normal The ECM detects the following conditions:
The ARD glow plug voltage is greater than 15 VDC for at least 5 second.
The ECM has been powered for at least 2 seconds.
There are no active 168 diagnostic codes.
The warning lamp will come on.
The code will reset when the keyswitch is cycled or if the voltage is within normal operating range. The ECM receives electrical power (battery voltage) through the wiring that is supplied by the manufacturer of the application. Battery+ voltage is supplied through P1:19.The battery- is supplied through the following terminals on the P1 connector:
P1:20
P1:39
P1:40
P1:59
P1:60
P1:79
P1:80The ECM receives the input from the keyswitch at P1:13 and P1:33 when the keyswitch is in the ON or START positions. When the ECM detects battery voltage at this input, the ECM will activate the main relay. When battery voltage is removed from this input, after a short time the ECM will deactivate the main relay.The cause of an intermittent power supply to the ECM can occur on either the positive side or the negative side of the battery circuit. The connections for the unswitched battery+ may be routed through a dedicated protection device (circuit breaker).Some applications may be equipped with an engine protection shutdown system or an idle timer shutdown system that interrupts electrical power to the keyswitch. The engine protection shutdown system can be an aftermarket device and the idle timer shutdown system can be external to the ECM. Some of these systems will not supply power to the ECM until one of the following conditions is met:
The engine is cranking.
An override button is pressed.These devices may be the cause of intermittent power to the ECM. These devices may also shutdown the engine.Usually, battery power to the diagnostic connector is available and the battery power to the data link connector is independent of the keyswitch. Therefore, although the electronic service tool can be powered up, there may be no communication with the engine ECM. The engine ECM requires the keyswitch to be in the ON position to maintain communications. The ECM may power down a short time after connecting the electronic service tool if the keyswitch is in the OFF position.
Illustration 1 g03325323
Schematic for the ignition keyswitch and battery supply circuit
Illustration 2 g03325729
View of the pin locations on the P1 connector for the ignition keyswitch and battery supply circuit
(3) Main relay -
(4) Main relay +
(12) Engine start signal
(13) Ignition keyswitch
(19) Battery +
(20) Battery ground
(23) Main relay -
(33) Ignition keyswitch
(39) Battery ground
(40) Battery ground
(59) Battery ground
(60) Battery ground
(79) Battery ground
(80) Battery groundTest Step 1. Inspect Electrical Connectors and Wiring
Check the fuses.
Thoroughly inspect the battery connections and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:
P1:19 (Battery+)
P1: 20, 39, 40. 59, 60, 79, 80 (Battery-)
P1:4 (ECM main relay +)
P1:3, 23 (ECM main relay -)
P1:13, 33 (keyswitch)
Check the harness for abrasion and for pinch points from the battery to the ECM, and from the keyswitch to the ECM.Results:
All connectors, pins, and sockets are correctly connected and/or inserted and the harness is free of corrosion, of abrasion or of pinch points. - Proceed to Test Step 2.
There is a fault with the connectors and/or the harness. - Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all the seals are correctly in place and ensure that the connectors are correctly connected. Replace any blown fuses.Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOPTest Step 2. Check for Active Diagnostic Codes
Connect the electronic service