3847844 Volvo.Penta Tachometer kit

Table 1
Diagnostic Trouble Codes for the Ignition Keyswitch and the Battery Supply Circuit    
J1939 Code    Description    Notes    
168-2     Battery Potential / Power Input 1 : Erratic, Intermittent or Incorrect     This code indicates that the battery circuit for the ECM is intermittent while the engine is running.
The ECM detects the following conditions:
Three voltage readings that are below 6 VDC in a period of 7 seconds will be detected by the ECM. The voltage must then increase to more than 9 VDC.
The keyswitch is in the ON position.
The engine is running.
The engine is not cranking.
The diagnostic code will normally be logged. If the battery voltage disappears without returning, the ECM will not log this diagnostic code and the engine will shut down. This shutdown will depend on the length of time for the occurrence of the fault.
The check engine lamp and the warning lamp may come on.
The engine may experience changes in the engine rpm, and intermittent engine shutdowns. The ECM may stop injecting fuel, dependent on the length of time for the occurrence of the fault.    
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 to the ECM exceeds 32 VDC for more than 0.5 seconds.
The keyswitch is in the ON position.
The engine is not cranking.
The engine has been running for more than 30 seconds.
The ECM will log the diagnostic code. If equipped, the warning lamp may come on.    
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 to the ECM is below 18 VDC for more than 0.5 seconds.
The keyswitch is in the ON position.
The engine is not cranking.
The engine has been running for more than 3 seconds.
If equipped, the warning lamp may come on. The ECM will normally log the diagnostic code. If battery voltage disappears without returning, the ECM will not log this diagnostic code and the engine will shut down.
The engine will derate 100 percent.
The engine may experience changes in the engine rpm and intermittent engine shutdowns.    The ECM receives electrical power (battery voltage) through the wiring that is supplied by the manufacturer of the application. Unswitched battery+ voltage is supplied through P1: 48, 52, 53, 55, and 57. The battery- is supplied through P1: 61, 63, 65, 67, and 69. The ECM receives the input 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 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.
The engine oil pressure achieves acceptable limits.
An override button is pressed.These devices may be the cause of intermittent power to the ECM. These devices may also shut down 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 in order 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.For intermittent faults such as intermittent shutdowns that could be caused by the application wiring, temporarily bypassing the application wiring may be an effective means of determining the root cause. If the symptoms disappear with the bypass wiring, the application wiring is the cause of the fault. A means of bypassing the application wiring is explained in this test procedure. This procedure is especially important for applications that do not provide dedicated circuits for the unswitched battery and the connections for the keyswitch.
Illustration 1 g02456140
Schematic for the ignition keyswitch and battery supply circuit
Illustration 2 g01981196
View of the pin locations on the P1 connector for the ignition keyswitch and battery supply circuit (48) Battery+ (52) Battery+ (53) Battery+ (55) Battery+ (57) Battery+ (61) Battery ground (63) Battery ground (65) Battery ground (67) Battery ground (69) Battery ground (70) Ignition key switchTest Step 1. Inspect Electrical Connectors and Wiring
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: 48, 52, 53, 55, 57 (Unswitched Battery+)
P1: 61, 63, 65, 67, 69 (Battery-)
P1:70 (keyswitch)
Use the electronic service tool to perform a "Wiggle Test".
Check the ECM connector for the correct torque of 6 N m (53 lb in).
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 of the