C175 Tier 4 Final Engines for Off-Highway Trucks Caterpillar

Speed/Timing - Test

Usage:

793F D3T

Use this procedure to troubleshoot a problem with one or more of the engine speed/timing sensors. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
190-8 Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	190-8 Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	The Electronic Control Module (ECM) can default to the secondary engine speed/timing sensor. The default will occur if a valid signal is not received from the primary engine speed/timing sensor. The engine will shutdown only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal. The code is logged.
637-11 Engine Timing Sensor : Other Failure Mode	261-11 Engine Timing Offset Fault	The ECM has detected that the crankshaft speed/timing sensor and the camshaft speed/timing sensor are not aligned. The code is logged.
723-8 Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	342-8 Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	If a valid signal is not received from the secondary engine speed/timing sensor, the ECM will default to the primary engine speed/timing sensor. The engine will shutdown only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal. The code is logged.
4202-8 Engine Speed Sensor #3 : Abnormal Frequency, Pulse Width, or Period	2710-8 Engine Tertiary Speed Sensor : Abnormal Frequency, Pulse Width, or Period	The signal from the tertiary speed/timing sensor is ignored. The engine speed is calculated by using the signal from the primary speed/timing sensor. If the signal from the primary speed/timing sensor is ignored, the engine speed is calculated by using the signal from the secondary speed/timing sensor.
4202-11 Engine Speed Sensor #3 : Other Failure Mode	2710-11 Engine Timing Offset fault	The ECM has detected that the crankshaft speed/timing sensor and the camshaft speed/timing sensor are not aligned.

The Electronic Control Module (ECM) uses the pattern of the pulses from the speed/timing sensors to determine the position of the crankshaft and camshaft. The ECM measures the time between the pulses that are created by the sensors as the gears rotate to determine rpm.

After locating the No. 1 cylinder, the ECM triggers each injector in the correct firing order and at the correct unit injector timing. The actual timing and duration of each injection is based on engine rpm and load.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET). B. Determine if a code is active or logged.	Codes	Result: A -8 code is active or logged. Proceed to Test Step 2. Result: A -11 code is active or logged. Proceed to Test Step 6.
2. Check the Engine Speed/Timing Circuit A. Connect Cat ET. B. Start the engine and run the engine. The problem may occur when the engine is at any operating temperature. However, the problem is more likely to occur when the engine is at the normal operating temperature.	Circuit Check	Result: The engine started. Proceed to Test Step 3. Result: The engine did not start. Proceed to Test Step 4.
3. Check for Codes A. While the engine is running, monitor Cat ET for active codes. B. Use Cat ET to monitor the "Engine Starting" screen for the following: - An engine speed/timing that is "Not Detected".	Codes	Result: There is an active code or there is a timing pattern that is "Not Detected". Proceed to Test Step 6. Result: There is not an active code and there is not a timing pattern that is "Not Detected". Repair: Download the "Product Status Report" from the engine ECM. Troubleshoot any diagnostic codes that may be present. Return to service.
4. Check the Battery Voltage A. Connect Cat ET. B. Use Cat ET to monitor the "Engine Starting" screen for the following: - Battery voltage C. Crank the engine for 5 seconds.	Battery Voltage	Result: The battery voltage is OK. Proceed to Test Step 5. Result: The battery voltage is NOT OK. Repair: Refer to Troubleshooting, "Engine Cranks but Does Not Start" for additional information. Verify that the repair eliminated the problem.
5. Check the Engine Speed and the Engine Speed/Timing Status A. Connect Cat ET. B. Use Cat ET to monitor the "Engine Starting" screen for the following: - Cranking speed C. Crank the engine for 5 seconds. While the engine is cranking, verify that the sensors show an acceptable cranking speed. D. While the engine is cranking, check the status of the engine speed/timing.	Speed/Timing Status	Result: A sensor does not show an acceptable cranking speed and/or the timing pattern shows "Not Detected". Proceed to Test Step 6. Result: The sensors show an acceptable cranking speed. The timing pattern shows "Detected". Repair: Refer to Troubleshooting, "Engine Cranks but Does Not Start" for additional information. Verify that the repair eliminated the problem.
6. Inspect the Sensor Assembly A. Turn the keyswitch to the OFF position. B. Visually inspect the sensor and the sensor assembly without removing the sensor assembly from the engine. Flanges must be flush against the surface of the front timing gear housing to ensure proper operation. C. Inspect the bracket. Verify that the bracket securely holds the flanges of the sensors flush against the engine. D. 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. E. Disconnect the harness from the speed/timing sensors. Check the harness for debris and for corrosion. F. Perform a 45 N (10 lb) pull test on the harness wiring.	Sensor	Result: The sensor and the sensor assembly mounting are OK. Do not reconnect the harness connector. Proceed to Test Step 7. Result: The sensor and/or the sensor assembly has a mechanical problem or the harness has debris and/or corrosion. Repair: Repair or replace the sensor and/or the sensor assembly. Repair: Replace the sensor and the sensor harness connector if there was debris and/or corrosion. Verify that the repair eliminated the problem.
7. Use a Multimeter to Check the Harness Wiring A. Disconnect the affected speed/timing sensor from the wiring harness. B. Turn the keyswitch to the ON position. C. Perform the following procedure for the affected sensor: For 2 wire speed/timing sensors: a. Measure the voltage between terminal 1 on the engine wiring harness connector and a known good ground. The voltage should be 2.5V. +/- 0.2V. b. Measure the voltage between terminal 2 on the engine wiring harness connector and a known good ground. The voltage should be 2.5V. +/- 0.2V. For 3 wire speed/timing sensors: a. Measure the voltage between terminal A (8V SUPPLY) and terminal B (RETURN). The voltage should be 8V +/-.2V. b. Measure the voltage between terminal C (SIGNAL) and terminal B (RETURN). The voltage should be 2.5V. +/- 0.2V.	Wiring Harness	Result: A -8 code was active and the voltage was OK for all the measurements. Repair: Replace the affected speed/timing sensor. Result: A -11 code was active and the voltage was OK for all the measurements. Repair: Refer to Testing and Adjusting, Camshaft Timing. Result: The voltage was not OK for at least one of the measurements. There is a problem in the harness wiring. Repair: Repair or replace the appropriate harness wiring. 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).