Detonation sensors are located on the upper cylinder block between every two cylinders. Each sensor monitors two adjacent cylinders. For example, one sensor monitors cylinders 1 and 3.
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| Illustration 1 | g01093730 |
Arrangement of the detonation sensors (A-E) Detonation sensors | |
The master Electronic Control Module (ECM) and the slave ECM supply 8 VDC to each detonation sensor. The detonation sensors provide electrical signals to each ECM that indicate mechanical engine vibrations. The signals are amplified and the signals are filtered. The frequency of the signal corresponds to the mechanical frequency of the vibrations. The amplitude of the signal is proportional to the intensity of the vibrations.
The master ECM monitors the detonation sensors on the left side of the engine. The slave ECM monitors the detonation sensors on the right side of the engine. The signals are monitored in order to determine the presence and the severity of the detonation. The master ECM can retard the timing of the cylinders on the left side of the engine in order to limit detonation levels. The slave ECM can retard the timing of the cylinders on the right side of the engine in order to limit detonation levels. The timing may be retarded for a single cylinder or for more than one cylinder. The timing may be retarded for all of the cylinders, if necessary. If retardation of the timing does not sufficiently limit the detonation, the master ECM will shut down the engine.
An ECM can retard timing by as few as three degrees for light detonation levels. The timing can be retarded up to six degrees for severe detonation. For most applications, the minimum allowable actual timing is ten degrees BTC (five degrees BTC for propane operation). A proportional strategy is used for advancing the timing after the timing has been retarded. The rate of advance is based upon the level of detonation. The rate is faster for lighter detonation. The fastest rate of proportional timing advance is one degree per minute.
Each ECM will diagnose the detonation sensors for a signal that is shorted to the -Battery side, the +Battery side, or an open circuit. To avoid detecting vibrations that are not related to detonation, each ECM only monitors a detonation sensor when one of the pistons that is monitored by that sensor is between 5 degrees after top center and 40 degrees after top center on the power stroke. Therefore, the "Block Tap" method of testing the detonation sensors does not work for the G3500B Engine.
An input from a detonation sensor that is diagnosed by an ECM as "open/shorted to +battery" may measure 0 VDC on a voltmeter. This is caused by the lack of pull up resistors in the detonation sensor's circuits inside the ECM.
Each ECM also supports related event codes when the levels of detonation warrant a reaction from the ECM. If the timing has been retarded by the maximum amount and the level of detonation remains high, the master ECM will shut down the engine. Detonation protection is disabled when the engine speed is less than 250 rpm.
Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.
The most likely causes of the diagnostic code are a poor connection or a problem in a wiring harness. The next likely cause is a problem with a sensor. The least likely cause is a problem with an ECM.
The 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.
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| Illustration 2 | g01087497 |
Schematic for the detonation sensors | |
Test Step 1. Inspect the Electrical Connectors and Wiring
- Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.
- Thoroughly inspect each of the following connectors:
- Master ECM J2/P2 connectors
- J6/P6 connectors on the terminal box for the master ECM
- J4/P4 connectors for the slave ECM
- J12/P12 connectors on the terminal box for the slave ECM
- Connectors for each of the detonation sensors
- Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the detonation sensors.
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Illustration 5 g00985646
Harness side of the side of the master ECM P2 connector
(P2-36) Signal for cylinders 2 and 4
(P2-37) Signal for cylinders 6 and 8
(P2-38) Signal for cylinders 10 and 12
(P2-39) Signal for cylinders 14 and 16
(P2-44) Signal for cylinders 18 and 20
(P2-54) Return
(P2-55) Return
(P2-56) 8 volt supply
(P2-57) 8 volt supply
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Illustration 6 g00902248
Harness side of the side of the P6 connector
(J6-B) Signal for cylinders 2 and 4
(J6-C) Signal for cylinders 6 and 8
(J6-D) Signal for cylinders 10 and 12
(J6-G) Signal for cylinders 14 and 16
(J6-H) Signal for cylinders 18 and 20
(J6-A) Return
(J6-E) Return
(J6-J) 8 volt supply
(J6-F) 8 volt supply
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Harness side of the P4 connector for the slave ECM
(P4-36) Signal for cylinders 1 and 3
(P4-37) Signal for cylinders 5 and 7
(P4-38) Signal for cylinders 9 and 11
(P4-39) Signal for cylinders 13 and 15
(P4-44) Signal for cylinders 17 and 19
(P4-54) Return
(P4-55) Return
(P4-56) 8 volt supply
(P4-57) 8 volt supply
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Harness side of the side of the P21 connector
(J12-B) Signal for cylinders 1 and 3
(J12-C) Signal for cylinders 5 and 7
(J12-D) Signal for cylinders 9 and 11
(J12-G) Signal for cylinders 13 and 15
(J12-H) Signal for cylinders 17 and 19
(J12-A) Return
(J12-E) Return
(J12-J) 8 volt supply
(J12-F) 8 volt supply
- Check the harness and wiring for abrasion and for pinch points from the detonation sensors to each ECM.
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Illustration 9 g01087510
Detonation sensors
- Make sure that the detonation sensors are properly installed according to the torque in Specifications, "Detonation Sensors".
- Master ECM J2/P2 connectors
Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
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| Illustration 3 | g01087500 |
Terminal box for the master ECM (1) J2/P2 connectors for the master ECM (2) J6/P6 connectors for the harness to the detonation sensors on the left side of the engine | |
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| Illustration 4 | g01087506 |
Terminal box for the slave ECM (3) J4/P4 connectors for the slave ECM (4) J12/P12 connectors for the detonation sensors on the right side of the engine | |
Expected Result:
All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. All of the detonation sensors are properly installed.
Results:
- OK - The components are in good condition with proper connections. Proceed to Test Step 2.
- Not OK - The components are not in good condition and/or at least one connection is improper.
Repair: Perform the necessary repairs and/or replace parts, if necessary.
Stop.
Test Step 2. Check for Diagnostic Codes for the 8 Volt DC Supply
- Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".
- Restore the electrical power to the engine. Set the engine control to the STOP mode.
- Observe the "Active Diagnostic" screen of Cat ET. Wait at least 30 seconds so that any codes may become activated. Look for these codes:
- "41-03 8 Volt DC Supply short to +batt"
- "41-04 8 Volt DC Supply short to ground"
- "41-03 8 Volt DC Supply short to +batt"
Expected Result:
Neither of the "8 Volt DC Supply" diagnostic codes are active.
Results:
- OK - Neither of the "8 Volt DC Supply" diagnostic codes are active. Proceed to Test Step 3.
- Not OK - At least one of the "8 Volt DC Supply" diagnostic codes is active.
Repair: The "8 Volt DC Supply" diagnostic code must be resolved before you can proceed with this functional test.Exit this procedure and refer to Troubleshooting, "+8V Sensor Voltage Supply".If necessary, return to this functional test in order to troubleshoot the detonation sensor after the "8 Volt DC Supply" diagnostic code has been resolved.
Stop.
Test Step 3. Check for Active Diagnostic Codes for the Detonation Sensors
- Start the engine and run the engine.
Note: The run relay and the crank terminate relay must be energized before a diagnostic code for a detonation sensor can be generated. Therefore, the engine must be running. The engine will shut down soon after the diagnostic code for the detonation sensor is activated.
- Allow a minimum of 30 seconds for any diagnostic codes to become active. Observe the "Active Diagnostic" screen of Cat ET and look for the diagnostic codes that are listed in Table 1:
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Table 1 Code Description Cylinders 1501-03 Cylinder #1 Detonation Sensor short to +batt 1 and 3 1501-04 Cylinder #1 Detonation Sensor short to ground 1502-03 Cylinder #2 Detonation Sensor short to +batt 2 and 4 1502-04 Cylinder #2 Detonation Sensor short to ground 1505-03 Cylinder #5 Detonation Sensor short to +batt 5 and 7 1505-04 Cylinder #5 Detonation Sensor short to ground 1506-03 Cylinder #6 Detonation Sensor short to +batt 6 and 8 1506-04 Cylinder #6 Detonation Sensor short to ground 1509-03 Cylinder #9 Detonation Sensor short to +batt 9 and 11 1509-04 Cylinder #9 Detonation Sensor short to ground 1510-03 Cylinder #10 Detonation Sensor short to +batt 10 and 12 1510-04 Cylinder #10 Detonation Sensor short to ground 1513-03 Cylinder #13 Detonation Sensor short to +batt 13 and 15 1513-04 Cylinder #13 Detonation Sensor short to ground 1514-03 Cylinder #14 Detonation Sensor short to +batt 14 and 16 1514-04 Cylinder #14 Detonation Sensor short to ground 1517-03 Cylinder #17 Detonation Sensor short to +batt 17 and 19 1517-04 Cylinder #17 Detonation Sensor short to ground 1518-03 Cylinder #18 Detonation Sensor short to +batt 18 and 20 1518-04 Cylinder #18 Detonation Sensor short to ground Note: A "short to ground" diagnostic code can indicate either an actual short to ground or an open circuit.
Expected Result:
None of the above diagnostic codes are active.
Results:
- OK (No active codes) - None of the above codes are active at this time. The problem seems to be resolved. The original diagnostic code was probably caused by a poor electrical connection in one of the harness connectors.
Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If any of the above codes are logged and the engine is running properly, there may be an intermittent problem in a connector or on a wiring harness. Refer to Troubleshooting, "Inspecting Electrical Connectors".
Stop.
- Not OK (Active Code) - A "short to +batt" or "short to ground" diagnostic code was activated.
Repair: Note the diagnostic code and note the location of the suspect detonation sensor.
Proceed to Test Step 4.
Test Step 4. Verify the Presence of the Supply Voltage at the Sensor
- Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.
- Disconnect the detonation sensor with the diagnostic code.
- Restore the electrical power to the engine. Set the engine control to the STOP mode.
- Measure the voltage between terminals A and B on the harness connector for the sensor.
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| Illustration 10 | g00890518 |
Harness connector for the detonation sensors (A) 8 volt supply (B) Return (C) Signal | |
Expected Result:
The voltage is between 7.6 VDC and 8.4 VDC.
Results:
- OK - The voltage is between 7.6 VDC and 8.4 VDC. The correct voltage is available to the sensor. Do not reconnect the sensor. Proceed to Test Step 5.
- Not OK - The voltage is not between 7.6 VDC and 8.4 VDC. The correct voltage is not available to the sensor. There is probably an open circuit in the 8 volt supply or in the return for the sensor.
Repair: The open circuit may be caused by a poor electrical connection or a wiring problem between the ECM and the connector for the sensor.If only one detonation sensor has a diagnostic code, the open circuit for the 8 volt supply is in the engine harness. Repair the electrical connection and/or the wiring, when possible. Replace the harness, if necessary.
Stop.
Test Step 5. Measure the Voltage of the Signal Wire at the Sensor
- Measure the voltage between terminals B and C on the harness connector for the suspect sensor.
| | |
| Illustration 11 | g00890518 |
Harness connector for the detonation sensors (A) 8 volt supply (B) Return (C) Signal | |
Expected Result:
The voltage is between 0.4 VDC and 0.6 VDC.
Results:
- Yes - The voltage is between 0.4 VDC and 0.6 VDC.
Repair: Reconnect the suspect sensor. Start the engine again and check for the diagnostic code.If the diagnostic code recurs, replace the detonation sensor with a known good detonation sensor. Tighten the detonation sensor according to the torque in Specifications, "Detonation Sensor". Verify that the problem is resolved.
Stop.
- No - The voltage is not between 0.4 VDC and 0.6 VDC. If the voltage is less than 0.4 VDC, there is probably a short to ground or an open circuit between the connector for the detonation sensor and the ECM. If the voltage is greater than 4.8 VDC, there is probably a short circuit to a positive voltage between the connector for the detonation sensor and the ECM. If you are troubleshooting a detonation sensor for the master ECM, proceed to Test Step 6. If you are troubleshooting a detonation sensor for the slave ECM, proceed to Test Step 7.
Test Step 6. Check the Operation of the Master ECM
- Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.
- Use a 151-6320 Wire Removal Tool to remove the signal wire for the suspect sensor from the P2 connector.
- Restore the electrical power to the engine. Set the engine control to the STOP mode.
- Start the engine. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.
An active "open/short to +batt" diagnostic code is generated for the sensor.
Note: The run relay and the crank terminate relay must be energized before a diagnostic code for a detonation sensor can be generated. Therefore, the engine must be running. The engine will shut down soon after the diagnostic code for the detonation sensor is activated.
- Set the engine control switch to the OFF/RESET mode.
- Fabricate a jumper wire that is long enough to reach between the P1 connector and the P2 connector. Install Deutsch terminals on the ends. Install one end of jumper wire (2) into the terminal for the signal wire that was removed from P2 connector (1). Install the other end of the jumper wire into terminal 19 of P1 connector (3) .
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| Illustration 12 | g01087517 |
Terminal box for the master ECM (1) P2 connector (2) Jumper wire (3) P1 connector | |
- Start the engine. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.
An active "short to ground" diagnostic code is generated for the sensor.
Expected Result:
Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps.
Results:
- OK - Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps. The master ECM is operating correctly. There is probably an open circuit in a harness between the master ECM and the connector for the sensor. The problem could be inside the terminal box for the master ECM.
Repair: Remove the jumper wire. Insert the terminal that was removed from the P2 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector. Repair the harness, when possible. Replace the harness, if necessary.
Stop.
- Not OK - No active "open/short to +batt" and "short to ground" diagnostic codes were generated. The master ECM is not operating correctly.
Repair: It is unlikely that the master 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 master 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 7. Check the Operation of the Slave ECM
- Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.
- Use a 151-6320 Wire Removal Tool to remove the signal wire for the suspect sensor from the P4 connector.
- Restore the electrical power to the engine. Set the engine control to the STOP mode.
- Start the engine. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.
An active "open/short to +batt" diagnostic code is generated for the sensor.
Note: The run relay and the crank terminate relay must be energized before a diagnostic code for a detonation sensor can be generated. Therefore, the engine must be running. The engine will shut down soon after the diagnostic code for the detonation sensor is activated.
- Set the engine control to the OFF/RESET mode.
- Fabricate a jumper wire that is long enough to reach between the P4 connector and the P3 connector. Install Deutsch terminals on the ends. Install one end of jumper wire (2) into the terminal for the signal wire that was removed from P4 connector (1). Install the other end of the jumper wire into terminal 19 of P3 connector (3) .
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| Illustration 13 | g01087530 |
Terminal box for the slave ECM (1) P4 connector (2) Jumper wire (3) P3 connector | |
- Start the engine. Observe the "Active Diagnostic" screen on Cat ET. Allow a minimum of 30 seconds for any codes to activate.
An active "short to ground" diagnostic code is generated for the sensor.
Expected Result:
Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps.
Results:
- OK - Active "open/short to +batt" and "short to ground" diagnostic codes are generated according to the above steps. The slave ECM is operating correctly. There is probably an open circuit in the harness between the slave ECM and the connector for the sensor. The problem could be inside the terminal box for the slave ECM.
Repair: Remove the jumper wire. Insert the terminal that was removed from the P4 connector. Pull on the wire in order to verify that the terminal is fully inserted into the connector. Repair the harness, when possible. Replace the harness, if necessary.
Stop.
- Not OK - No active "open/short to +batt" and "short to ground" diagnostic codes were generated. The slave ECM is not operating correctly.
Repair: It is unlikely that the slave 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 slave 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.