60252A 2 Mercruiser END CAP/CONNECTOR, EXHAUST MANIFOLD (FRONT)

Table 1
J1939 Code and Description Comments
190-8
Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period The engine speed from this sensor is ignored.
The code is active.
The code is logged if the pattern from the timing ring returns for five seconds.
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 The code is latched in the active state until the power to the Electronic Control Module (ECM) is cycled.
The offset for the timing calibration is set to zero when the diagnostic code is active.
The sensor is ignored. The engine speed is calculated by using only the signal from the primary speed/timing sensor.
723-19
Engine Speed Sensor #2 : Data Error The ISM has lost the camshaft differential speed signal.
The ECM has been notified by the Integrated Sensing Module (ISM) that the engine speed signal is no longer detected.
The code is logged.
The engine is shutdown.
Illustration 1 g06408834
For the complete circuit details, refer to the full schematic.
The ECM provides the engine speed/timing sensors with a regulated voltage of 8.0 0.5 VDC. The engine speed/timing sensors provide a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensors. The timing reference gear is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference gear allows the ECM to determine the crankshaft position, rotation, and rpm.The engine speed/timing sensors generate a pulse signal to the ECM as each tooth passes the sensors. The ECM counts the pulses to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern to determine the crankshaft position. The ECM uses this information to determine the position of the No. 1 cylinder. The ECM then triggers each unit injector to fire in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM. The ECM uses engine rpm and engine load to determine the timing and duration of injection. The loss of a signal from an engine speed/timing sensor generates a diagnostic on Caterpillar Electronic Technician (ET). If the signals from both the primary engine speed/timing sensor and the secondary engine speed/timing sensor are lost, the ECM will terminate fuel injection.Under normal operation, the ECM utilizes the signal from the primary speed/timing sensor to determine the crankshaft position for an accurate fuel delivery and timing. This feature eliminates the need for a separate procedure for timing calibration. 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 primary engine speed/timing sensor is detected during engine start-up, timing calibration is aborted. The value of 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.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Start the engine.
C. Run the engine until normal operating temperature is reached.
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. Look for these codes and pattern status parameters on Cat ET:
Codes:
• 190–08
• 723–08
Parameters:
• "Primary Engine Speed Sensor Timing Pattern Status"
• "Secondary Engine Speed Sensor Timing Pattern Status"
Note: When checking status parameters, engine must be in a cranking state.
Codes
Result: None of the diagnostic codes that are listed above are active or logged and the primary/secondary speed sensor timing status is "OK".
Repair: If the diagnostic codes that are listed above are not active or logged as well as the primary/secondary speed sensor timing status is "OK", and the engine is not running properly, refer to the appropriate engine symptom in this Troubleshooting Manual.
Result: If a 190-08 or a 723-08 code is active or logged or primary/secondary speed sensor timing status is "Not OK".
Proceed to Test Step 2.
Result: No engine rpm. -Cat ET is not reporting engine rpm for at least one engine speed/timing sensor while the engine is cranked or at least one of the speed timing pattern status parameter are displayed as "Not OK".
Proceed to Test Step 3.
2. Check the Installation of the Sensor Assembly
A. Turn the main disconnect