G3516B Engines Caterpillar

+5V Sensor Voltage Supply

Usage:

System Operation Description:

The Electronic Control Module (ECM) supplies 5.0 ± 0.5 VDC to the sensors for these parameters:

Inlet air temperature
Engine oil temperature
Unfiltered engine oil pressure
Filtered engine oil pressure
Humidity (if equipped)

A "+5 V sensor supply" diagnostic code is probably caused by a short circuit or an open circuit in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide an historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.

This troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

"DESIRED SPEED" Potentiometer (if equipped)

The ECM also provides 5 VDC to the "DESIRED SPEED" potentiometer (if equipped).

A "5 Volt Sensor DC Power Supply short to +batt" diagnostic code will be activated if both of these conditions occur:

The desired speed signal wire is shorted to a voltage source that is greater than +5 volts.
The "DESIRED SPEED" potentiometer is near the maximum desired speed or at the maximum desired speed.

A "5 Volt Sensor DC Power Supply short to ground" diagnostic code will be activated if both of these conditions occur:

The desired speed signal wire is shorted to ground.
The "DESIRED SPEED" potentiometer is near the maximum desired speed or at the maximum desired speed.

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Illustration 1	g01078325
Schematic for the 5 volt supply

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 2	g01076892
Terminal box (1) J1/P1 connectors for the ECM (2) J12/P12 connectors for the harness from the sensors (3) 16 amp circuit breaker (4) J9/P9 connectors for the wiring to the customer's connections

Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (3) to the OFF position.
Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Thoroughly inspect each of the following connectors:
- J1/P1 connectors
- J9/P9 and J12/P12 connectors on the terminal box

Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).

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Illustration 3	g01053671
Harness side of the P1 connector (P1-2) 5 volt supply (P1-3) Return (P1-11) Signal for the humidity (P1-14) Signal for the inlet manifold air temperature (P1-16) Signal for the desired speed (P1-17) Signal for the engine oil temperature (P1-18) 5 volt supply (P1-24) Signal for the filtered engine oil pressure (P1-26) Signal for the unfiltered engine oil pressure (P1-35) Return

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Illustration 4	g00888444
Harness side of the P12 connector (P12-A) 5 volt supply (P12-C) Return (P12-E) Signal for the unfiltered engine oil pressure (P12-F) Signal for the filtered engine oil pressure (P12-G) Signal for the humidity (P12-H) Signal for the engine oil temperature (P12-K) Signal for the inlet air temperature

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Illustration 5	g01070999
Harness side of the P9 connector (P9-H) Return (P9-I) Signal for desired speed (P9-J) 5 volt supply

Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuits for the 5 volt sensors.
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Illustration 6 g01076893

Right side view
(5) Inlet air temperature sensor
(6) Engine coolant temperature sensor

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Illustration 7 g01076895

Left side view
(7) Unfiltered oil pressure sensor
(8) Filtered oil pressure sensor
(9) Oil temperature sensor

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Illustration 8 g01076896

Left side views of the 50 Hz and 60 Hz engines
(10) Humidity sensor (if equipped)
Check the harness and wiring for abrasion and for pinch points from each 5 volt sensor to the ECM.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

OK - All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. The components are in good condition with proper connections. Proceed to Test Step 2.
Not OK - At least one of the connectors, pins, or sockets are not connected properly. At least one of the connectors and the wiring has corrosion, abrasion, and/or pinch points.
Repair: Perform the necessary repairs and/or replace parts, if necessary.

STOP

Test Step 2. Check for Diagnostic Codes

Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".
Rotate the "DESIRED SPEED" potentiometer (if equipped) counterclockwise to the minimum speed position.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become activated. Look for these codes:
- 262-03 5 Volt Sensor DC Power Supply short to +batt
- 262-04 5 Volt Sensor DC Power Supply short to ground
Observe the "Logged Diagnostic" screen on Cat ET. Look for the same codes.

Expected Result:

The 262-03 code or the 262-04 code is not active or logged.

Results:

No codes - There are no active codes or logged codes. If the engine is equipped with a "DESIRED SPEED" potentiometer, proceed to Test Step 3. Otherwise, the initial diagnostic code was probably caused by a poor electrical connection. Resume normal operation. STOP.
Active code - The 262-03 code or the 262-04 code is active. Proceed to Test Step 5.
Logged code - The 262-03 code or the 262-04 code is not active. However, there is at least one logged code for the +5 volt sensor supply.
Repair: There may be a problem with the wiring and/or a connector. Refer to Troubleshooting, "Inspecting Electrical Connectors".

Verify that the wiring and/or connectors are OK. Check for diagnostic codes again. Proceed to Test Step 3, if necessary.

Test Step 3. Check the Analog Speed Circuit

Rotate the "DESIRED SPEED" potentiometer (if equipped) clockwise to the maximum speed position. Look for these codes:

262-03 5 Volt Sensor DC Power Supply short to +batt
262-04 5 Volt Sensor DC Power Supply short to ground

Expected Result:

The 262-03 code or the 262-04 code is not active.

Results:

No codes - Rotating the "DESIRED SPEED" potentiometer clockwise to the maximum speed position did not cause an active code. The +5 V sensor voltage supply is operating correctly at this time. Resume normal operation.
STOP
Active code - Rotating the "DESIRED SPEED" potentiometer clockwise to the maximum speed position caused an active code. There is a problem with the analog speed circuit. Proceed to Test Step 4.

Test Step 4. Check the Wiring for the "DESIRED SPEED" Potentiometer

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Label the wiring that is connected to the "DESIRED SPEED" potentiometer. Disconnect the wiring from the "DESIRED SPEED" potentiometer.
Disconnect the P1 connector.
Measure the resistance between terminal P1-16 and all of the other terminals on the P1 connector.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

OK - Each check of the resistance is greater than 20,000 Ohms. The wiring on the outside of the terminal box for the "DESIRED SPEED" potentiometer appears to be OK.
Repair: The "DESIRED SPEED" potentiometer may have a problem. Perform the following procedure:
1. Check the "DESIRED SPEED" potentiometer in order to ensure that the potentiometer does not have an internal short circuit. Replace the "DESIRED SPEED" potentiometer, if necessary. Continue with this procedure when the "DESIRED SPEED" potentiometer is operating correctly.
2. Reconnect the wiring to the "DESIRED SPEED" potentiometer. Be sure to connect the wires to the appropriate terminals.
3. Reconnect the P1 connector to the ECM.
4. Perform this entire procedure again. Verify that the original problem is resolved.
STOP
Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with the wiring for the "DESIRED SPEED" potentiometer. The problem could be between the P1 connector and the J9 connector. Alternatively, the problem could be in the P9 connector or the wiring that is connected to the P9 connector.
Repair: Perform any necessary repairs or replace parts, if necessary.

STOP

Test Step 5. Isolate the Wiring Harnesses from the ECM

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Reconnect the P1 connector to the ECM.
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Illustration 9 g00888555

ECM connector P1
(P1-2) 5 volt supply for the analog sensors
(P1-18) 5 volt supply for the "DESIRED SPEED" potentiometer
Use a 151-6320 Wire Removal Tool to remove terminals P1-2 and P1-18.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

No codes - The 262-03 code or the 262-04 code is not active. Disconnecting all of the 5 volt wiring from the ECM eliminated the active "5 Volt Sensor Supply" diagnostic code. There is a problem with a connector and/or the wiring in a harness. Proceed to Test Step 6.
Active code - The 262-03 code or the 262-04 code is active. Disconnecting all of the 5 volt wiring from the ECM did not eliminate the +5 V diagnostic code. There may be a problem with the ECM.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the problem is not resolved, perform the following steps:
Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".
If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM".

STOP

Test Step 6. Connect the 5 Volt Wiring for the Analog Speed Circuit to the ECM

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Insert terminal 18 into the P1 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector.
Rotate the "DESIRED SPEED" potentiometer clockwise to the maximum speed position.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

No codes - The 262-03 code or the 262-04 code is not active. Connecting the wiring for the analog speed circuit to the ECM did not cause a diagnostic code. The wiring for the analog speed circuit appears to be OK. Proceed to Test Step 7.
Active codes - The 262-03 code or the 262-04 code is active. Connecting the wiring for the analog speed circuit to the ECM caused a diagnostic code. Proceed to Test Step 4.

Test Step 7. Connect the 5 Volt Wiring for the Sensors to the ECM

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Insert terminal 2 into the P1 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Use Cat ET to look for diagnostic codes.

Expected Result:

No active codes

Results:

No codes - The 262-03 code or the 262-04 code is not active. Connecting the 5 VDC for the sensors did not cause a diagnostic code. The problem appears to be resolved.
Repair: The initial diagnostic code was probably caused by a poor electrical connection. Resume normal operation.

STOP
Active code - The 262-03 code or the 262-04 code is active. Connecting the 5 VDC for the sensors caused a diagnostic code. Proceed to Test Step 8.

Test Step 8. Disconnect the 5 Volt Sensors and Look for Active Diagnostic Codes.

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Disconnect the sensors for the following parameters:
- Inlet air temperature
- Engine oil temperature
- Unfiltered engine oil pressure
- Filtered engine oil pressure
- Humidity (if equipped)
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
Note: An "Open Circuit" code will be generated for each sensor that is disconnected. This is normal. Clear the codes after you complete this procedure.
Observe the "Active Diagnostic" screen on Cat ET. Verify that the 262-03 code or the 262-04 code is not active.
Reconnect the sensors for the following parameters one at a time. After you reconnect each sensor, wait for at least 30 seconds and then observe the "Active Diagnostic" screen on Cat ET.
- Inlet air temperature
- Engine oil temperature
- Unfiltered engine oil pressure
- Filtered engine oil pressure
- Humidity

Expected Result:

The original "5 Volt Sensor" diagnostic code is activated when a particular sensor is disconnected.

Results:

Yes - The original "5 Volt Sensor" diagnostic code is activated when a particular sensor is reconnected. The sensor and/or the wiring for the sensor has a short circuit.
Repair: Perform the following procedure:
1. Set the engine control to the OFF/RESET mode.
2. Disconnect the suspect sensor.
3. Set the engine control to the STOP mode. Use Cat ET to clear the logged 262-03 or 262-04 code.
4. Reconnect the suspect sensor. Verify that the diagnostic code recurs.
  If these conditions are true, replace the sensor.
5. Clear all of the diagnostic codes. Verify that the problem is eliminated.
STOP
No - The original "5 Volt Sensor" diagnostic code was still active while all of the 5 volt sensors were disconnected. Do not reconnect the sensors. Proceed to Test Step 9.

Test Step 9. Check the Harnesses

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Disconnect the P1 connector. Verify that all of the sensors for the following parameters are disconnected from the engine harness:
- Inlet air temperature
- Engine oil temperature
- Unfiltered engine oil pressure
- Filtered engine oil pressure
- Humidity
Measure the resistance between terminal P1-2 and each of the remaining terminals on the P1 connector. During each measurement, wiggle the harnesses in order to check for an intermittent problem with the harness. Be sure to wiggle the harnesses near each of the connectors for the disconnected sensors. Also, wiggle the harness at the P12 connector.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

OK - Each check of the resistance is greater than 20,000 Ohms. The 5 volt wires in the engine harnesses do not have a problem. The problem appears to be resolved. The initial diagnostic code was probably caused by a poor electrical connection.
Repair: Reconnect all of the connectors. Resume normal operation.

STOP
Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with a connector and/or at least one of the 5 volt wires in a harness. Proceed to Test Step 10.

Test Step 10. Check the Engine Harness

Disconnect the P12 connector. Verify that all of the sensors are disconnected.
Measure the resistance between terminal P12-A and each of the remaining terminals on the P12 connector. During each measurement, wiggle the harnesses in order to check for an intermittent problem with the harness. Be sure to wiggle the harnesses near each of the connectors.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

OK - Each check of the resistance is greater than 20,000 Ohms. The 5 volt wires in the engine harness do not have a problem. Proceed to Test Step 11.
Not OK - Repair the engine harness, when possible. Replace parts, if necessary.
STOP

Test Step 11. Check the Terminal Box's Harness

Disconnect the P9 connector. Verify that P12 and P1 are also disconnected. This will isolate the terminal box's harness.
Measure the resistance between terminal P1-2 and all of the other terminals on the P1 connector. During each measurement, wiggle the wires in the terminal box in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.
Measure the resistance between terminal P1-2 and the ground strap for the ECM.

Expected Result:

Each check of the resistance is greater than 20,000 Ohms.

Results:

OK - Each check of the resistance is greater than 20,000 Ohms. The problem seems to be resolved. The initial diagnostic code was probably caused by a poor electrical connection.
Repair: Reconnect all of the connectors and resume normal operation.

STOP
Not OK - At least one check of the resistance is less than 20,000 Ohms. There is a problem with a connector and/or at least one of the 5 volt wires in the terminal box.
Repair: Repair the terminal box's harness, when possible. Replace parts, if necessary.

STOP