3512C and 3516C Marine Auxiliary Engines Caterpillar

Speed/Timing - Test

Usage:

Use this procedure to troubleshoot the electrical system if a problem is suspected with one or more of the engine speed/timing sensors. Also, use this procedure if any of the diagnostic codes in Table 1 is active.

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Table 1
Diagnostic Codes Table
CDL Code and Description	Conditions which Generate the Code	System Response
190-8 Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	The Electronic Control Module (ECM) detects an abnormal signal frequency.	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.
723-8 Engine Speed Sensor #2 : Abnormal Frequency, Pulse Width, or Period	The ECM detects an abnormal signal frequency.	The code is latched in the active state until the power to the ECM is cycled. The offset for the timing calibration is set to zero while 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.

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 in order to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern in order 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.

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Illustration 1	g02968596
Schematic for the engine speed/timing sensors

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Illustration 2	g02724104
P2 ECM connector (P2-29) +8V supply (primary ECM) (P2-35) Primary engine speed/timing signal (primary and secondary ECM) (P2-46) Secondary engine speed/timing signal (primary and secondary ECM)

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Illustration 3	g02724105
P1 ECM connector (P1-5) Secondary digital return (primary ECM only) (P1-18) Primary digital return (primary ECM only)

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Diagnostic 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 while the engine is being cranked. If necessary, power Cat ET from another battery while the engine is being cranked. E. Look for these codes on Cat ET: - 190-08 - 723-08	Codes	Results: None of the diagnostic codes that are listed above are active or logged. Repair: If the diagnostic codes that are listed above are not active or logged, and the engine is not running properly, refer to the appropriate engine symptom in this Troubleshooting manual. Results: A 190-08 or a 723-08 code is active or logged. Proceed to Test Step 2. Results: No engine rpm. - Cat ET is not reporting engine rpm for at least one engine speed/timing sensor while 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	Results: The O-ring seals are properly installed. The bracket and the seals are free of damage. Repair: Perform the following procedure in order to install a sensor assembly: 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. Results: At least one of the sensor assembly components is not OK. Repair: Install a new sensor assembly. Verify that the repair eliminated the problem.
3. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the engine speed/timing sensors D. Check the allen head screw for each ECM connectors and the rail connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. E. Check the harness and wiring for abrasion and for pinch points from the engine speed/timing sensors to the ECM.	Circuit	Results: The harness and the wiring appear to be OK. Proceed to Test Step 4. Results: There is a problem in the connectors and/or wiring. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals for the connectors are properly in place and ensure that the connectors are coupled. Verify that the repair eliminated the problem.
4. Check the Supply Voltage to the Sensors A. Turn the main disconnect switch to the OFF position. B. Disconnect the connectors for the speed/timing sensors. C. Restore electrical power to the ECM. Measure the voltage between terminal A and terminal B at the sensor connectors.	Supply voltage	Results: The battery voltage is OK. Proceed to Test Step 5. Results: The battery voltage is not OK. Proceed to Test Step 7.
5. Check the Signal Voltage at the Sensor A. Crank the engine and measure the voltage between the sensor signal wire and terminal B.	Signal voltage	Results: The signal voltage is OK. The voltage measures less than 3 VDC or more than 9 VDC when the ECM is powered and the engine is not cranking. While the engine is cranking, the voltage is between 2 VDC and 7 VDC. Proceed to Test Step 6. Results: The signal voltage is not OK. Repair: Replace the engine speed/timing sensor. A timing calibration is not required when the sensors are replaced. Verify that the repair eliminated the problem.
6. Check the Signal Voltage at the ECM A. Turn the main disconnect switch to the OFF position. B. Remove the signal wire from the ECM connector P2-35. C. Restore electrical power to the ECM. D. Crank the engine and measure the voltage between the primary sensor signal wire and P1-18. E. Turn the main disconnect switch to the OFF position. F. Remove the signal wire from the ECM connector P2-46. G. Restore electrical power to the ECM. H. Crank the engine and measure the voltage between the secondary sensor signal wire and P1-5.	ECM signal voltage	Results: The signal voltage is OK. The voltage measures less than 3 VDC or more than 9 VDC when the ECM is powered and the engine is not cranking. While the engine is cranking, the voltage is between 2 VDC and 7 VDC. Proceed to Test Step 7. Results: The signal voltage is not OK. There is a problem in the engine speed/timing circuit. Repair: The problem is between the ECM and the engine speed/timing sensor. Repair the connectors and/or wiring or replace the connectors and/or wiring. Verify that the repair eliminated the problem.
7. Check the Supply Voltage for the Engine Speed/Timing Sensors at the ECM A. Turn the main disconnect switch to the OFF position. B. Remove the supply wire from ECM connector P2-29. Install a wire jumper into the socket P1-29. C. Reconnect ECM connector J2/P2. D. Restore electrical power to the ECM. E. Measure the supply voltage between the wire in ECM connector P2-5 and the wire jumper in P2-29.	ECM supply voltage	Results: The supply voltage is OK. There is an open circuit or a short circuit between the ECM and the connectors for the engine speed/timing sensors. Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring. Verify that the repair eliminated the problem. Results: The supply voltage is not OK. There appears to be a problem with the ECM. Repair: Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. Verify that the repair eliminated the problem.