WASHER 6N8863 - Caterpillar

System Operation Description:Use this procedure to troubleshoot any suspect problems with the following sensors:
Primary engine speed/timing sensor
Secondary engine speed/timing sensorThis procedure covers the following diagnostic codes:
190-08 Engine Speed abnormal
342-08 Secondary Engine Speed signal abnormalThe engine uses two engine speed/timing sensors. The primary engine speed/timing sensor detects the reference for engine speed and timing from a unique pattern on the crankshaft gear. The secondary engine speed/timing sensor detects the reference for engine speed and timing from a unique pattern on the camshaft gear. The ECM counts the time between pulses that is created by the sensor as the gear rotates in order to determine rpm.Under normal operation, the secondary engine speed/timing sensor is used to determine timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to determine engine speed.When the timing has been established, the ECM triggers each injector in the correct firing order at the correct time. The actual timing and duration of each injection is based on engine rpm and on load. If the engine is running and the signal from one sensor is lost, no noticeable change in engine performance will be noticed. If the engine is running and the signals from both sensors are lost, fuel injection will be terminated and the engine will be shut down by the ECM. The engine will start when only one sensor signal is present. The engine will not start if the signals from both sensors are lost.Both sensors are magnetic sensors. The two sensors are not interchangeable. If a sensor is replaced, a timing calibration is not necessary.If a replacement of the ECM is required, the ECM parameters and the timing calibration can be transferred from the suspect ECM to the replacement ECM. Timing calibration will not be necessary. This feature requires the Caterpillar Electronic Technician (ET) and this feature is only possible if the existing ECM can communicate with Cat ET. Use the "Copy Configuration - ECM Replacement" feature on Cat ET.Complete all of the following tasks when you install a speed/timing sensor:
Ensure that an O-ring is installed on the sensor. If the O-ring is damaged or missing, replace the O-ring.
Lubricate the O-ring with oil.
Ensure that the sensor is fully seated into the engine before tightening the bracket bolt.
Ensure that the electrical connector is latched.
Ensure that the harness is properly secured, and ensure that each tie-wrap is placed in the correct location.
Illustration 1 g01129099
Schematic for the engine speed/timing sensorsTest Step 1. Check for Diagnostic Codes
Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".
Turn the keyswitch to the ON position.
Start the engine and run the engine until the engine is at the normal operating temperature.Note: If the engine will not start, monitor the engine rpm on Cat ET while the engine is being cranked. Cat ET may need to be