9562A 1 Mercruiser CARBURETOR ASSEMBLY

Table 1
J1939 Code and Description Comments
731-3
Engine Knock Sensor : Voltage Above Normal The engine ECM detects signal voltage that is not in the acceptable range.
The code is logged.
731-4
Engine Knock Sensor : Voltage Below Normal The engine ECM detects signal voltage that is not in the acceptable range.
The code is logged.
6651-3
Engine Knock #2 : Voltage Above Normal The engine ECM detects signal voltage that is not in the acceptable range.
The code is logged.
6651-4
Engine Knock #2 : Voltage Below Normal The engine ECM detects signal voltage that is not in the acceptable range.
The code is logged. The engine ECM receives and processes detonation information directly from the sensor.The ECM supplies 8 VDC to power the sensors. The detonation sensors provide electrical signals to the module 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 to determine the presence and the severity of the detonation. The ECM can retard the timing of the cylinders 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 the cylinders, if necessary. If retardation of the timing does not sufficiently limit the detonation, the ECM will shut down the engine.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 on 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, to the +Battery side, or for an open circuit. To avoid detecting vibrations that are not related to detonation, the ECM only monitors a detonation sensor when one of the pistons that is monitored by that sensor is between top center and 40 degrees after top center on the power stroke. Therefore, the “Block Tap” method of testing the detonation sensors cannot be performed on this 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. The cause is the lack of a pull-up resistors in the detonation sensor circuit 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 a historical record. Before you begin this procedure, use the Cat® Electronic Technician (Cat ET) Service Tool 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.
Illustration 1 g06487420
For the complete circuit details, refer to the full schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect the Cat® Electronic Technician (Cat ET) Service Tool to the service tool connector.
B. Determine if a code is active or logged.
Codes
Result: A -3 code is active.
Proceed to Test Step 2.
Result: A -4 code is active.
Proceed to Test Step 3.
2. Create a Short at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the sensor with the active -3 code.
C. Install the jumper wire between the following terminals at the sensor connector:
- Terminal C (signal) and Terminal B (sensor return)
D. Connect Cat ET.
E. Use Cat ET to monitor the following:
- -4 code
F. Turn the keyswitch to the OFF position.
Create a Short
Result: A -4 code did not become active.
Proceed to Test Step 4.
Result: A -4 code became active.
Repair: The wiring harness is OK. Replace the sensor.
Verify that the repair eliminated the problem.
3. Create an Open at the Sensor Connector
A. Turn the keyswitch to the OFF position.
B. Disconnect the sensor with the active -4 code.
C. Connect Cat ET.
D. Use Cat ET to monitor the following:
- -3 code
E. Turn the keyswitch to the OFF position.
Create an Open
Result: A -3 code did not become active.
Proceed to Test Step 4.
Result: A -3 code became active.
Repair: The wiring harness is OK. Replace the sensor.
Verify that the repair eliminated the problem.
4. Check the 8 VDC Supply Voltage at the Sensor Connector
A. Turn the keyswitch to the ON position.
B. Measure the voltage at the sensor connector between the following pins:
- Pin A and Pin B
C. Reconnect the sensor.
8.0 0.2 VDC
Result: The supply voltage is 8.0 0.2 VDC.
Proceed to Test Step 5.
Result: The supply voltage is not 8.0 0.2 VDC.
Repair:Repair or replace the wiring harness.
If the problem is not resolved, proceed to Test Step 5.
5. Perform the Wiggle Test
Carefully following this procedure is the best way to identify the root cause of an intermittent problem.
A. Connect Cat ET.
B. Use CAT ET to perform the following test:
- "Wiggle Test"
C. Slowly wiggle the wiring and the connectors between the L-C2 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all the wiring.
As you wiggle the wiring look for these problems:
- Loose connectors or damaged connectors
- Moisture on the connectors or the wiring
- Damaged that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring
- Damaged insulation
Test
Result: The wiring failed the Wiggle Test.
Repair: There is a problem with the wiring harness. Repair or replace the wiring harness.
Verify that the repair eliminated the problem.
Result: