303.5E2 CR Mini-HEX Machine ECM Caterpillar

Sensor Signal (Analog, Passive) - Test

Usage:

Machine ECM

The following is a list of codes that are associated with the passive (analog) circuits of the machine.

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Table 1
Machine ECM (MID 39)
DTC	Code Description	System Response
96-3	Fuel Level Sensor : Voltage Above Normal	Fuel gauge indicator will report incorrectly.
96-4	Fuel Level Sensor : Voltage Below Normal	Fuel gauge indicator will report incorrectly.
110-3	Engine Coolant Temperature Sensor : Voltage Above Normal	Engine coolant temperature reading is erratic, possibly resulting a shutdown of the engine by the Machine ECM. The Operator Monitor displays a popup symbol in gray when this diagnostic code is active. The Operator Monitor Warning LED displays in red when this code is active.
110-4	Engine Coolant Temperature Sensor : Voltage Below Normal	Engine coolant temperature reading is erratic, possibly resulting a shutdown of the engine by the Machine ECM. The Operator Monitor displays a popup symbol in gray when this diagnostic code is active. The Operator Monitor Warning LED displays in red when this code is active.
600-3	Hydraulic Oil Temperature Sensor : Voltage Above Normal	The code is logged. The Operator Monitor displays a popup symbol in amber when this diagnostic code is active. The Operator Monitor Warning LED displays in red when this code is active.
600-4	Hydraulic Oil Temperature Sensor : Voltage Below Normal	The code is logged. The Operator Monitor displays a popup symbol in amber when this diagnostic code is active. The Operator Monitor Warning LED displays in red when this code is active.

Possible causes for an FMI 3 Diagnostic code are:

The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the +battery.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 4 Diagnostic code are:

The sensor has failed.
The signal circuit for the sensor is shorted to ground.
The Machine ECM has failed. A failure of the Machine ECM is unlikely.

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Illustration 1	g06037883
Schematic of the Analog, Passive Sensor connections at the Operator Monitor.

Note: The diagram above is a simplified schematic of the fuel level sensor, and the hydraulic oil temperature sensor connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. For detailed information, refer to the latest revision of Electrical Schematic, UENR6662 for the 305.5E2 CR excavator.

The tables below provide information about the resistance across a given sensor based on environmental conditions or fluid level.

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Table 2
Fuel Level Sensor Resistance Values
Float Position	Resistance (Ω)
Empty Tank (bottom)	246-252
Full Tank (top)	27-33

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Table 3
Engine Coolant Temperature Sensor Resistance Values
C°	F°	Resistance (k Ω)
25	77	7.6
40	104	4.0
50	122	2.7 ±0.22
80	176	0.92 ±0.073
95	203	0.56
105	221	0.42
120	248	0.276 ±0.014

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Table 4
Hydraulic Oil Temperature Sensor Resistance Values
C°	F°	Resistance (Ω)
-20	-4	9717
0	32	3268
20	68	1249
40	104	532
60	140	248
80	176	126
100	212	68
120	248	39

Diagnostic Trouble Code Procedure

Note: Prior to beginning this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.

FMI 3 diagnostic code, proceed to Table 5.
FMI 4 diagnostic code, proceed to Table 6.

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Table 5
FMI 3 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Sensor Note: Refer to the appropriate table within this procedure for a list of resistance values related to the suspect sensor. Perform any temperature readings or confirm fluid level depending on the type of sensor being checked. A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the sensor from the harness. C. Measure the resistance between pin 1 and 2 of the sensor.	The resistance reading agrees with the values from the table.	OK - The resistance readings agree with the values in the specific table. Proceed to Test Step 2. NOT OK - The resistance readings do not agree with the values in the table. Repair: Replace the sensor. Proceed to Test Step 4.
2. Check For An Open In The Sensor Circuit A. The key start switch and disconnect switch remain in the OFF position. B. The harness connector remains disconnected from the sensor. C. At the sensor harness connector, install a jumper wire across pins 1 and 2. D. Disconnect the connectors from the ECM. E. At the ECM harness connector, measure the resistance between the signal and return contacts for the sensor.	The resistance reading is less than 5 Ω.	OK - The resistance is less than 5 Ω. Proceed to Test Step 3. NOT OK - The resistance is greater than 5 Ω. The open is in the signal circuit or the return circuit. Repair: Repair or replace the harness. Proceed to Test Step 4.
3. Check The Signal Circuit For A Short. A. The disconnect switch and the key start switch remain in the OFF position. B. The harness connectors remain disconnected from the ECM. C. Remove the jumper wire from the sensor harness connector. D. At the ECM harness connectors, measure the resistance between the signal circuit and all the other contacts on the ECM.	Each resistance reading is greater than 5K Ω.	OK - Each measurement is greater than 5K Ω. Proceed to Test Step 4. NOT OK - A resistance measurement is less than 5 Ω. A short exists between the signal circuit and the circuit with the low-resistance measurement. Repair: Repair or replace the machine harness. Proceed to Test Step 4.
4. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch to the ON position. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

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Table 6
FMI 4 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Sensor A. Turn the key start switch and disconnect switch to the ON position. B. Ensure that the diagnostic code is active. C. Disconnect sensor from machine harness.	The diagnostic code remains active.	OK - Diagnostic code remains active. Proceed to Test Step 2 NOT OK - Diagnostic code is no longer active. Repair: Replace the sensor. Proceed to Test Step 3.
2. Check The Wiring Harness Of The Sensor For A Short To Ground A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the machine harness connector from the sensor. C. Disconnect the machine harness connectors from the ECM. D. At the ECM harness connectors, measure the resistance between the signal circuit and all the other contacts that are used on the ECM.	Each reading greater than 5K Ω.	OK - All resistance readings are greater than 5K Ω. Proceed to Test Step 3. NOT OK - One or more of the readings are less than 5 Ω. A short exists between the signal contact and the circuit with the low resistance. Repair: Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose connection or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit. Proceed to Test Step 3.
3. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch to the ON position. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist currently. The initial diagnostic code may have been caused by a poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.