TUBE 1998207 - Caterpillar

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.
Table 1
J1939 Code and Description CDL Code and Description Comments
190-8
Engine Speed : Abnormal Frequency, Pulse Width, or Period 190-8
Engine Speed : 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 shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal.
The code is logged.
723-8
Engine Speed Sensor #2 : Abnormal Frequency, Pulse Width, or Period 342-8
Engine Speed Sensor #2 : 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 shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal.
The code is logged.
Illustration 1 g03871359
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 while the engine is being cranked. If necessary, power Cat ET from another battery while the engine is being cranked.
D. Determine if a code is active or logged.
Codes
Result: A -8 code is not active or logged.
Repair: Refer to the appropriate engine symptom in this Troubleshooting manual.
Result: A -8 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.
C. Remove the 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 OK.
Repair: Install a new sensor assembly.
If the problem is not resolved, proceed to Test Step 3.
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 additional information.
C. Perform a 45 N (10 lb) pull test on the connector wires.
D. Check the