3512C Marine Auxiliary Generator Set Engines with Dynamic Gas Blending Caterpillar

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 the following diagnostic code is active or easily repeated.

Table 1

Diagnostic Codes Table
J1939 Code and Description	Conditions which Generate this 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 is set to zero rpm. 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 sensor with a regulated voltage of 8.0 ± 0.5 VDC. The engine speed/timing sensor provides a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensor. 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 sensor generates a pulse signal to the ECM as each tooth passes the sensor. 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 signal from the engine speed/timing sensor is lost, the ECM will terminate fuel injection. A manual timing calibration is required on this engine.

Illustration 1	g03656801
Schematic for the engine speed/timing sensors

Illustration 2	g03381708
(1) Secondary engine speed/timing sensor (2) Primary engine speed/timing sensor

Illustration 3	g03381711
(3) Timing calibration sensor

Illustration 4	g03381773
P2 ECM connector (P2-26) Secondary engine speed/timing signal (P2-46) Primary engine speed/timing signal

Illustration 5	g03381777
P1 ECM connector (P1-4) +8V digital supply (P1-5) Digital return

Illustration 6	g03393169

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 while the engine is being cranked. If necessary, power Cat ET from another battery while the engine is being cranked. D. Look for these codes on Cat ET: - 190-08 - 723-08	Codes	Result: A code is not 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. Result: A 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 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	Result: 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. Result: 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.	Connectors and Wiring	Result: The connectors and/or wiring appear to be OK. Proceed to Test Step 4. Result: 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	Result: The battery voltage is OK. Proceed to Test Step 5. Result: 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	Result: 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. Result: 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 P2-46. C. Restore electrical power to the ECM. D. Crank the engine and measure the voltage between the primary sensor signal wire and P1-5.	Signal Voltage	Result: 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. Result: 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 P1-4. Install a wire jumper into the socket P1-4. C. Reconnect ECM connector J1/P1. D. Restore electrical power to the ECM. E. Measure the supply voltage between the wire in ECM connector P1-5 and the wire jumper in P1-4.	Supply Voltage	Result: 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. Result: 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.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).