G3516B Engines Caterpillar

Detonation Sensors

Usage:

System Operation Description:

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	g01071661
Configuration of the detonation sensors

The Electronic Control Module (ECM) supplies 8 VDC in order to power the sensors. The detonation sensors provide electrical signals to the ECM that indicate mechanical engine vibrations. Each sensor outputs an electrical signal. The signal is amplified and the signal is 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 ECM monitors the signals in order to determine the presence and the severity of the detonation. The ECM retards the timing 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 engine is shut down.

The 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.

The 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, the ECM only monitors a detonation sensor on the power stroke, when one of the sensor's cylinders is between 5 degrees and 40 degrees after top center. 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 the 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.

The 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 ECM will shut down the engine. Detonation protection is disabled when the engine speed is less than 250 rpm.

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.

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 the 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	g01106035
Schematic for the detonation sensors

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 3	g01071625
Terminal box (1) ECM connectors J2/P2 (2) J11/P11 connectors for the harness from the detonation sensors (3) 16 amp circuit breaker

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:

J2/P2 connectors
J11/P11 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 4	g01071626
Harness side of the side of the P2 connector (P2-36) Signal from the detonation sensor for cylinders 1 and 3 (P2-37) Signal from the detonation sensor for cylinders 5 and 7 (P2-38) Signal from the detonation sensor for cylinders 9 and 11 (P2-39) Signal from the detonation sensor for cylinders 13 and 15 (P2-44) Signal from the detonation sensor for cylinders 2 and 4 (P2-45) Signal from the detonation sensor for cylinders 6 and 8 (P2-46) Signal from the detonation sensor for cylinders 10 and 12 (P2-47) Signal from the detonation sensor for cylinders 14 and 16 (P2-54) Return for the detonation sensors on the right side of the engine (P2-55) Return for the detonation sensors on the left side of the engine (P2-56) 8 volt supply for the detonation sensors on the right side of the engine (P2-57) 8 volt supply for the detonation sensors on the right side of the engine

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Illustration 5	g00890429
Harness side of the side of the P11 connector (J11-B) Signal from the detonation sensor for cylinders 1 and 3 (J11-C) Signal from the detonation sensor for cylinders 5 and 7 (J11-D) Signal from the detonation sensor for cylinders 9 and 11 (J11-G) Signal from the detonation sensor for cylinders 13 and 15 (J11-L) Signal from the detonation sensor for cylinders 14 and 16 (J11-K) Signal from the detonation sensor for cylinders 10 and 12 (J11-I) Signal from the detonation sensor for cylinders 6 and 8 (J11-H) Signal from the detonation sensor for cylinders 2 and 4 (J11-A) Return for the detonation sensors on the right side of the engine (J11-E) Return for the detonation sensors on the left side of the engine (J11-J) 8 volt supply for the detonation sensors on the right side of the engine (J11-F) 8 volt supply for the detonation sensors on the left side of the engine

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 6 g00752902

Detonation sensors
Check the harness and wiring for abrasion and for pinch points from the detonation sensors to the ECM.
Make sure that the detonation sensors are properly installed according to the torque in Specifications, "Detonation Sensors".

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. 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 V Sensor Supply

Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".
Switch the 16 amp circuit breaker ON. 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"

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

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.

Start the engine and run the engine.

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	1 and 3
1502-03	Cylinder #2 Detonation Sensor short to +batt	2 and 4
1502-04	Cylinder #2 Detonation Sensor short to ground	2 and 4
1505-03	Cylinder #5 Detonation Sensor short to +batt	5 and 7
1505-04	Cylinder #5 Detonation Sensor short to ground	5 and 7
1506-03	Cylinder #6 Detonation Sensor short to +batt	6 and 8
1506-04	Cylinder #6 Detonation Sensor short to ground	6 and 8
1509-03	Cylinder #9 Detonation Sensor short to +batt	9 and 11
1509-04	Cylinder #9 Detonation Sensor short to ground	9 and 11
1510-03	Cylinder #10 Detonation Sensor short to +batt	10 and 12
1510-04	Cylinder #10 Detonation Sensor short to ground	10 and 12
1513-03	Cylinder #13 Detonation Sensor short to +batt	13 and 15
1513-04	Cylinder #13 Detonation Sensor short to ground	13 and 15
1514-03	Cylinder #14 Detonation Sensor short to +batt	14 and 16
1514-04	Cylinder #14 Detonation Sensor short to ground	14 and 16

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 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. Switch the 16 amp circuit breaker OFF.
Disconnect the sensor with the diagnostic code.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
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Illustration 7 g00890518

Harness connector for a detonation sensor
(A) 8 volt supply
(B) Return
(C) Signal
Measure the voltage between terminals "A" and "B" on the harness connector for the sensor.

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 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.

If more than one detonation sensor has a diagnostic code, use the following procedure to locate the open circuit for the +8 volt supply:

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.
Disconnect the P11 connector.
Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
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Illustration 8 g01076952

Side view of the terminal box and the J11 connector

Measure the voltage between the terminals that are listed in Table 2.

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Table 2
Points for the Measurement of Voltage
Connector and Terminal	Connector and Terminal
J11-J 8 volt supply for the detonation sensors on the right side of the engine	J11-A Return for the detonation sensors on the right side of the engine
J11-F 8 volt supply for the detonation sensors on the left side of the engine	J11-E Return for the detonation sensors on the left side of the engine

If both of the voltage measurements are between 7.6 VDC and 8.4 VDC, the open circuit is in the engine harness. Repair the engine harness, when possible. Replace the harness, if necessary.

If either of the voltage measurements are not between 7.6 VDC and 8.4 VDC, the open circuit is in the terminal box's harness. Repair the terminal box's harness, when possible. Replace parts, if necessary.

STOP

Test Step 5. Measure the Voltage of the Signal Wire at the Sensor

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Illustration 9	g00890518
Harness connector for a detonation sensor (A) 8 volt supply (B) Return (C) Signal

Measure the voltage between terminals (B) and (C) on the harness connector for the suspect sensor.

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 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 source between the connector for the detonation sensor and the ECM. Proceed to Test Step 6.

Test Step 6. Check the Operation of the ECM

Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

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Illustration 10	g01071633
Harness side of the P2 connector (P2-36) Signal from the detonation sensor for cylinders 1 and 3 (P2-37) Signal from the detonation sensor for cylinders 5 and 7 (P2-38) Signal from the detonation sensor for cylinders 9 and 11 (P2-39) Signal from the detonation sensor for cylinders 13 and 15 (P2-44) Signal from the detonation sensor for cylinders 2 and 4 (P2-45) Signal from the detonation sensor for cylinders 6 and 8 (P2-46) Signal from the detonation sensor for cylinders 10 and 12 (P2-47) Signal from the detonation sensor for cylinders 14 and 16

Use a 151-6320 Wire Removal Tool to remove the signal wire for the suspect sensor from the P2 connector.
Switch the 16 amp circuit breaker for the ECM ON. Set the engine control to the STOP mode.
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.
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.
Set the engine control to the OFF/RESET mode.
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Illustration 11 g01071656

Terminal box
(1) P2 connector
(2) Jumper wire
(3) P1 connector
Fabricate a jumper wire (2) that is long enough to reach between P2 connector (1) and P1 connector (3). Install Deutsch terminals on the ends of the jumper wire. Install one end of the jumper wire into the terminal for the signal wire that was removed from the P2 connector. Install the other end of the jumper wire into terminal 19 of the 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 ECM is operating correctly. There is probably an open circuit in the engine harness between the ECM and the connector for the sensor.
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 parts, if necessary.

STOP
Not OK - No active "open/short to +batt" and "short to ground" diagnostic codes were generated. The ECM is not operating correctly.
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