0334343 JOHNSON BAFFLE-EXH RELIEF

Table 1
J1939 Code and Description Comments
190-8
Engine Speed : Abnormal Frequency, Pulse Width, or Period Code is for the crankshaft sensor.
The ECM has lost the crankshaft sensor signal.
The engine is shutdown.
The code is logged.
637-11
Engine Timing Sensor : Other Failure Mode The engine has failed the automatic timing calibration during engine start-up.
The code is logged.
The value of the timing offset that has been stored in memory will be used. This value will continue to be used for the timing calibration until the diagnostic is resolved.
723-8
Engine Speed Sensor #2 : Abnormal Frequency, Pulse Width, or Period Code is for the camshaft sensor.
The engine is shutdown.
The code is logged. This engine utilizes two speed/timing sensors to detect the speed and the timing for the engine. The primary (camshaft) speed/timing sensor is used to detect engine speed and camshaft position during engine starting and also while the engine is running. The secondary (crankshaft) speed timing sensor is used only during engine cranking in order to determine top center of the No. 1 cylinder. Use this procedure to troubleshoot electrical problems with the circuit for the primary (camshaft) engine speed/timing sensor. For information related to troubleshooting the secondary engine speed/timing sensor, refer to Troubleshooting, "Speed/Timing (Secondary) - Test".
Illustration 1 g02644586
Features machined into the cam gear for speed/timing detection
The primary speed timing sensor utilizes a series of holes that are machined into the face of the cam gear to establish a signal. The pattern of holes includes two holes that are strategically spaced in order to provide a unique signal pattern to the ECM. The ECM utilizes the signal pattern to locate top center for the No. 1 cylinder, initiate ignition for the cylinders, and for engine speed determination.
Illustration 2 g02644459
Features machined into the flywheel for speed/timing detection
Similarly, the secondary speed timing sensor utilizes a series of holes that are machined into the outer surface of the flywheel to establish a signal. The pattern of holes includes two holes that are strategically spaced in order to provide a unique signal pattern to the ECM. The ECM utilizes the signal pattern to locate top center for the No. 1 cylinder.If the ECM detects a problem with the primary speed/timing sensor signal, the engine will not start and the engine will not run. If the ECM loses the signal from the secondary speed/timing sensor with the engine stopped, the engine will not be able to start. If a problem with the signal from the secondary speed/timing sensor occurs while the engine is running, the engine will continue to run.A timing offset is determined during each engine start-up. The value of the timing offset is stored in the non-volatile memory of the ECM until the successful completion of the next engine start-up. If a failure mode for the crankshaft speed/timing sensor is detected during engine start-up, the timing offset stored in ECM memory will be used. This value will continue to be used for the engine timing calibration until the diagnostic is resolved. A timing calibration cannot be performed manually on this engine.Note: The primary speed/timing sensor is an active 2 wire sensor that utilizes an 8 V supply voltage and integrated circuitry. Do not attempt to troubleshoot the sensor by measuring resistance across the terminals of the sensor.If a problem is detected with the signal from the speed/timing sensor during engine operation, the ECM will shut down the engine. The ECM activates the above diagnostic code.A timing offset is determined during each engine start-up. The value of the timing offset is stored in the non-volatile memory of the ECM until the successful completion of the next engine start-up. If a failure mode for the crankshaft speed/timing sensor is detected during engine start-up, the timing offset stored in ECM memory will be used. This value will continue to be used for the engine timing calibration until the diagnostic is resolved. A timing calibration cannot be performed manually on this engine.The least likely cause of this diagnostic code is a problem with the ECM.
Illustration 3 g06302203
For the complete circuit details, refer to the full schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Active Codes and Logged Codes
A. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Restore electrical power to the ECM.
C. Start the engine and run the engine until the engine is at normal operating temperature.
Note: If the engine will not start, monitor the engine rpm on Cat ET when the engine is being cranked. If necessary, power Cat ET from another battery when the engine is being cranked.
D. Determine if a code is active or logged.
Codes
Result: A code is not active or logged.
Repair: Refer to the appropriate engine symptom in this Troubleshooting manual.
Result: A 190-08, 723-08 code is active or logged.
Proceed to Test Step 2.
Result: No engine rpm. Cat ET is not reporting engine rpm for at least one engine speed/timing sensor when the engine is cranked.
Proceed to Test Step 3.
2. Check the Installation of the Sensor Assembly
A. Turn the main disconnect switch to the OFF position.
B. Visually inspect the sensors without removing the sensor assembly from the engine.
Verify that the bracket securely holds the flange of the sensor flush against the mounting surface.
Verify that the bracket is not bent. If the bracket is bent or if an obstruction is preventing the sensor assembly from being installed correctly, the engine will not start.
Note: The bracket cannot be replaced separately.
C. Remove the suspect engine speed/timing sensor from the engine.
D. Ensure that the O-ring seals are installed and free of damage.
Sensor
Result: The O-ring seals are properly installed. The bracket and the seals are free of damage.
Repair: Perform the following procedure:
1. Lubricate the O-ring seals with oil.
2. Fully seat the sensor into the housing.
Note: If the sensor assembly will not fully seat into the engine, replace the sensor assembly.
3. Tighten the bolts.
4. Connect the connector.
5. Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location.
Proceed to Test Step 3.
Result: At least one of the sensor assembly components is NOT