G3306B Petroleum Generator Set Engines Caterpillar

Sensor Supply - Test

Usage:

Use this procedure to troubleshoot the electrical system if a problem is suspected with one of the supply circuits. Also, use this procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.

Show/hide table

Table 1
Diagnostic Codes Table
Code and Description	Conditions which Generate this Code	System Response
3509-3 Sensor Supply Voltage 1 : Voltage Above Normal	The Electronic Control Module (ECM) detects a voltage for the 5 V power supply that is above 5.2 V for one second.	The code is logged. The amber warning lamp is illuminated. The ECM will use the last good value for each parameter that uses the 5 V supply. The service tool displays "Data Error" on the status screen for all of the 8 V sensors and the sensor supply.
3509-4 Sensor Supply Voltage 1 : Voltage Below Normal	The ECM detects a voltage for the 5 V power supply that is below 4.8 V for one second.	The code is logged. The amber warning lamp is illuminated. The ECM will use the last good value for each parameter that uses the 5 V supply. The service tool displays "Data Error" on the status screen for all of the 8 V sensors and the sensor supply. The ECM retries the circuit at two second intervals in order to recheck the circuit.
3511-6 Sensor Supply Voltage 3 : Current Above Normal	While the output driver for the oxygen sensors is on, the ECM detects a high current in the circuit for two seconds.	The code is logged. The amber warning lamp is illuminated. The activation of this code is latched by the ECM. The power to the ECM must be powered in order to reset the power supply.

24 V Power Supply

The ECM supplies 24 VDC to the voltage converter for the oxygen sensors through terminal location P1-28 at the ECM.

The 3511-6 becomes activated if a short to ground is detected in the harness between the ECM and the voltage converter.

8 V Power Supply

The ECM supplies 8 VDC to the speed/timing sensor.

For information that is related to troubleshooting the circuit for the speed/timing sensor, refer to Troubleshooting, "Speed/Timing - Test" for details.

5 V Power Supply

The ECM supplies 5.0 ± 0.5 VDC to the following sensors:

Engine oil pressure sensor
Intake manifold pressure sensor
Temperature sensor at the inlet of the catalytic converter
Temperature sensor at the outlet of the catalytic converter

The ECM also provides 5.0 ± 0.5 VDC to the speed control potentiometer.

There are five outputs at the ECM for the 5 V sensor supply:

J1-41
J1-42
J2-46
J2-48

The internal circuitry for the outputs is wired to the same voltage source inside the ECM. A short circuit on one of these terminals will cause a short circuit on the other terminal.

A 3509-4 Sensor Supply Voltage 1 : Voltage Below Normal will be activated if the following conditions occur:

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

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

Show/hide table




Illustration 1	g02073254
Schematic for the power supply circuits

Show/hide table




Illustration 2	g01960583
Locations of the engine sensors that are associated with the sensor supply circuits (typical left side engine view) (1) Intake manifold pressure sensor

Show/hide table




Illustration 3	g03431239
Locations of the engine sensors that are associated with the sensor supply circuits (typical right side engine view) (2) Voltage converter (3) Engine oil pressure sensor

Show/hide table




Illustration 4	g02073953
Locations of the ECM connectors that are associated with the sensor supply circuits (typical right side engine view) (4) J2/P2 ECM connector (5) J1/P1 ECM connector (6) Interconnect harness connector

Show/hide table




Illustration 5	g02073973
Terminal locations at the P1 ECM connector that are for the sensor supply circuit (P1-29) 24 V supply for the voltage converter (P1-34) Return for the temperature sensors that are for the catalytic converter (P1-41) 5 V supply for the temperature sensors that are for the catalytic converter (P1-42) 5 V supply for the intake manifold pressure sensor

Show/hide table




Illustration 6	g02074022
Terminal locations at the P2 ECM connector that are for the sensor supply circuit (P2-37) Return for the intake manifold pressure sensor (P2-38) Return for the engine oil pressure sensor (P2-40) Return for the desired speed signal (P2-46) 5 V supply for the engine oil pressure sensor (P2-48) 5 V supply for the desired speed signal

Show/hide table




Illustration 7	g02074056
Terminal locations at the interconnect harness connector that are for the speed adjust potentiometer (Terminal g) Return for the speed adjust potentiometer (Terminal N) Supply for the speed adjust potentiometer

Show/hide table




Illustration 8	g02074077
Terminal locations at the connector for the sensors that are for the catalytic converter (Terminal A) 5 V supply for the temperature sensor that is at the inlet of the catalytic converter (Terminal B) Return for the temperature sensor that is at the inlet of the catalytic converter (Terminal D) 5 V supply for the temperature sensor that is at the outlet of the catalytic converter (Terminal E) Return for the temperature sensor that is at the outlet of the catalytic converter

Show/hide table




Illustration 9	g01414254
Terminal locations for the harness connectors of the sensors (Terminal A) Supply (Terminal B) Return

Show/hide table

Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Set the engine control switch to the OFF position. Remove the electrical power from the engine. B. Thoroughly inspect the condition of the connectors that are for sensors (1) and (3) . Inspect the condition of connectors (2) that are at the voltage converter and connectors (6) that are for the interconnect harness. Also, thoroughly inspect the condition of ECM connectors (4) and (5) . Refer to Testing and Adjusting, "Electrical Connectors - Inspect". C. Perform a 45 N (10 lb) pull test on each of the wires in each of the circuits. D. Check the torque of the allen head screws for each of the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. E. Check the harness and the wiring for abrasion and for pinch points from the sensors to the appropriate junction box.	Damaged connector or wiring	Result: All 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. Result: At least one of the connectors, pins, and sockets are not connected properly. At least one of the connectors and/or the wiring has corrosion, abrasion, and/or pinch points. Perform the necessary repairs and/or replace parts, if necessary.

Show/hide table

Table 3
Troubleshooting Test Steps	Values	Results
2. Check for Diagnostic Codes A. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools". B. Restore the electrical power to the engine. Set the engine control to the STOP position. C. Monitor the active diagnostic code screen on Cat ET. Check and record any diagnostic codes that are active or logged. Look for the following diagnostic codes: Wait at least 30 seconds in order for diagnostic codes to become active. · 678-3 · 678-4 · 3509-3 · 3509-4 · 3511-6 D. Adjust the potentiometer from the maximum speed setting to the minimum speed setting while you check for active diagnostic codes. Ensure that the adjustment of the speed potentiometer is not the cause of the active diagnostic code. E. Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.	Diagnostic code	Result: None of the diagnostic codes for the sensor supply are active at this time. Use the "Logged Diagnostic" screen on Cat ET to check for logged codes. Look for the same codes that are listed above. If any of the above codes are logged while the engine is running properly, there may be an intermittent electrical problem in the circuit. Check the circuit connectors and the harnesses for the intermittent electrical problem. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for troubleshooting information. Result: A 678-3 or 678-4 diagnostic code is active at this time. The 8 V power supply is used to supply power to the speed/timing sensor. For information that is related to troubleshooting the circuit for the speed/timing sensor, refer to Troubleshooting, "Speed/Timing - Test". Result: A 3509-3 or 3509-4 diagnostic code is active at this time. There is a problem with one of the 24 V supply circuit for the voltage converter. Proceed to Test Step 3. Result: A 3511-6 diagnostic code is active at this time. There is a problem with one of the 24 V supply circuit for the voltage converter. Proceed to Test Step 5.

Show/hide table

Table 4
Troubleshooting Test Steps	Values	Results
3. Disconnect the 5 V Sensors, the Voltage Converter, and the Speed Potentiometer while you Monitor the Active Diagnostic Codes A. Restore the electrical power to the engine. Set the engine control to the STOP position. B. Monitor the active diagnostic code screen on Cat ET while you disconnect each 5 V sensor at the sensor connector. Disconnect the wiring for the desired speed potentiometer at the potentiometer. Check for an active 3509-3 code or an active 3509-4 code after you disconnect each of the following components: Wait at least 30 seconds in order for the diagnostic code to become active. · Engine oil pressure sensor · Intake manifold pressure sensor · Temperature sensor at the inlet of the catalytic converter · Temperature sensor at the outlet of the catalytic converter · Speed control potentiometer C. Set the engine control to the OFF position. Remove the electrical power from the engine.	Suspect component	Result: The diagnostic code deactivates when a particular sensor or the speed potentiometer is disconnected. Connect the suspect component. If the code returns, replace the component. Connect all of the connectors. Verify that the problem is resolved. Result: The diagnostic code remains active after all of the 5 V components are disconnected. There may be a problem in the harness wiring. Leave all of the components disconnected. Proceed to Test Step 4.
4. Measure the Voltage of the 5 V Supplies at the ECM A. Disconnect the J1/P1 and J2/P2 ECM connectors. B. Fabricate two jumper wires that are long enough to be used to create test circuits at the ECM connector. Crimp connector sockets to one end of each of the jumper wires. C. Restore the electrical power to the engine. Set the engine control to the STOP position. D. Use the jumper wires to measure the supply voltage at the ECM. Perform the measurements between the following terminals at the ECM: Several diagnostic codes that are unrelated to the power supply will become active when the ECM is powered. Disregard these codes while you perform the voltage measurements. If necessary, clear the codes when the test is finished. · J1-41 and J1-34 · J1-42 and J2-37 · J2-46 and J2-38 · J1-48 and J2-40 E. Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.	5.0 ± 0.2 VDC	Result: The voltage measurements are 5.0 ± 0.2 VDC. The ECM is operating correctly. There may be a supply wire that is shorted to another wire in the harness. There may be a supply wire that is shorted to engine ground. There may be an open circuit in one of the supply wires that are in the harness. Repair the harness, when possible. Replace the harness, if necessary. Verify that the original problem has been resolved. Result: The ECM is not generating the correct supply voltage. There is a problem with the ECM. Perform the following steps: Temporarily install a new ECM. Refer to Troubleshooting, "ECM - Replace". 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, "ECM - Replace".

Show/hide table

Table 5
Troubleshooting Test Steps	Values	Results
5. Disconnect the Voltage Converter while you Monitor the Active Diagnostic Codes A. Restore the electrical power to the engine. Set the engine control to the STOP position. B. Monitor the active diagnostic code screen on Cat ET while you disconnect the voltage converter. C. Disconnect the connector for the voltage converter at the converter. D. Check for an active 3511-6 diagnostic code. Wait at least 30 seconds in order for the diagnostic codes to become active. E. Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.	Voltage converter	Result: The 3511-6 diagnostic code deactivates when the voltage converter is disconnected. Reconnect the voltage converter. Check for the active code. If the code returns, replace the voltage converter. Verify that the problem is resolved. Result: The 3511-6 diagnostic code remains active after the voltage converter is disconnected. The voltage converter is not the cause of the diagnostic code. Leave the connectors disconnected. Proceed to Test Step 6.
6. Measure the Voltage for the 24 V Supply at the ECM A. Set the engine control to the OFF/RESET position. Ensure that the electrical power has been removed from the engine. B. Disconnect the J1/P1 ECM connectors. C. Fabricate a jumper wire that is long enough to be used to create a test circuit at the J1 ECM connector. Crimp a connector socket to one end of the jumper wire. D. Install the jumper wire at terminal location J1-29 (24 V supply) at the ECM. E. Restore the electrical power to the engine. Set the engine control to the STOP position. F. Measure the voltage between the jumper wire in P1-29 and a good source of battery ground. G. Remove electrical power from the ECM. Restore all wiring to the original configuration.	24.0 ± 0.8 VDC	Result: The voltage measurement is 24.0 ± 0.8 VDC. The ECM is operating correctly. The supply wire for the voltage converter is shorted to another wire in the harness or the supply wire is shorted to engine ground. Repair the harness, when possible. Replace the harness, if necessary. Verify that the original problem has been resolved. Result: The voltage measurement is not 24.0 ± 0.8 VDC. The ECM is not generating the correct supply voltage. There is a problem with the ECM. Perform the following steps: Temporarily install a new ECM. Refer to Troubleshooting, "ECM - Replace". 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, "ECM - Replace".