3AC-77375-0 Tohatsu O-RING, 2-28-5

Table 1
Diagnostic Codes
J1939 Code Description
38-3 Secondary Fuel Level : Voltage Above Normal
38-4 Secondary Fuel Level : Voltage Below Normal
96-3 Fuel Level : Voltage Above Normal
96-4 Fuel Level : Voltage Below Normal Background InformationThe Engine Control Module (ECM) has inputs for two fuel level sensors. The sensors read the level of fuel in the primary fuel tank and secondary fuel tank. The sensors are installed by the Original Equipment Manufacturer (OEM).Configuration Parameters - The "Primary Fuel Tank Size" and "Secondary Fuel Tank Size" parameters must be programmed to "25", "35", or "50" gallons for this feature to work. These parameters may be protected by customer passwords.-3 and -4 Codes - The ECM continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects voltage that is above a threshold on the signal wire, the ECM activates a -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a -4 diagnostic code.The following components can cause these codes:
Electrical connector or wiring
Sensor
ECMThe most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.Diagnostics on the Caterpillar Electronic Technician (ET)Wiggle Test - The wiggle test allows you to monitor the status of the signals from the sensors while you wiggle the wiring. This helps to identify faulty electrical connections.For additional information regarding the wiggle test, refer to the documentation that accompanies your Cat ET software.
Illustration 1 g01224893
Circuit connections for the fuel level sensors
Test Step 1. Determine if the Code is Logged or ActiveIdentify the diagnostic code.Results:
Logged -3 or -4 code - Repair: Do not troubleshoot a logged code unless the code relates to an engine symptom. If the code is logged and the code does not relate to an engine symptom, clear the code.If the code is logged and the code relates to an engine symptom, proceed to Test Step 2.
Active -3 code - Proceed to Test Step 3.
Active -4 code - Proceed to Test Step 6.Test Step 2. Wiggle the Wiring and Look for ProblemsCarefully following this procedure is a good way to identify the root cause of an intermittent problem.
Verify that the engine is OFF and that the keyswitch is ON.
Configure Cat ET for the wiggle test. Select the status group that includes the parameter that relates to the code. Start the wiggle test.
Slowly wiggle the wiring and the connectors between the P1 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring between the P1 connector and the sensor. As you wiggle the wiring, observe the wiring and the connectors. Look for these problems:
Loose connectors or damaged connectors
Moisture on the connectors or the wiring
Damage that is caused by excessive heat
Damage that is caused by chafing
Improper routing of wiring
Damaged insulationExpected Result:The wiring failed the wiggle test.Results:
The wiring failed the wiggle test. - Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.STOP
The wiring passed the wiggle test. - Repair: There may be a problem inside a connector. Perform the following procedure:
Disconnect the connectors for the sensor. Carefully inspect the terminals in each connector for proper installation. Each terminal must be clean and dry. Clean the terminals, if necessary.
Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
Turn the keyswitch to the OFF position.
Disconnect the J1/P1 connectors.
Illustration 2 g01225074
Terminal side of the P1 connector
Identify the P1 sockets that relate to the diagnostic code. Carefully inspect the sockets for proper installation. The sockets must be clean and dry. Clean the sockets, if necessary.
Insert a pin into each socket that relate to the diagnostic code. Verify that each socket grips the pin firmly. Repair any problems.
Connect all connectors.
Turn the keyswitch to the ON position.
Activate the wiggle test. Verify that the wiring passes the wiggle test.
Return the engine to service. STOPTest Step 3. Check for Battery Voltage on the Signal WireMeasure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.Expected Result:The voltage measurement is less than the +Battery voltage.Results:
Yes - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 4.
No - The voltage measurement is approximately equal to the +Battery voltage. The signal wire is shorted to the +Battery.Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.STOPTest Step 4. Check the Signal Wire for an Open Circuit
Disconnect the sensor that relates to the diagnostic code.
Connect a jumper wire between the two terminals on the harness connector for the sensor that relates to the diagnostic code. This will replace the sensor