HOSE AS 1087203 - Caterpillar

System Operation Description:Use this procedure under the following situation:
There is an active diagnostic code or an easily repeated diagnostic code that is associated with either the primary engine speed/timing sensor or the secondary engine speed/timing sensor.
You have been directed to this test from Troubleshooting, "Troubleshooting without a Diagnostic Code".The following background information is related to this procedure:The engine uses two engine speed/timing sensors. One sensor picks up the camshaft gear and the other sensor picks up the crankshaft gear. Both of the engine speed/timing sensors detect the reference for engine speed and timing from a unique pattern on the 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.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. If the engine is running and the signal from the primary engine speed/timing sensor is lost, a slight change in engine performance will be noticed when the ECM performs the changeover to the secondary engine speed/timing sensor. Loss of the signal from the secondary engine speed/timing sensor during engine operation will not result in any noticeable change in engine performance. However, if the signal from the secondary engine speed/timing sensor is not present during start-up the following conditions may exist:
The engine may require a slightly longer period of time to start-up.
The engine may run rough for a few seconds until the ECM determines the proper firing order with the primary engine speed/timing sensor.The engine will start and the engine will run when only one sensor signal is present from either of the sensors. The loss of the signal from both of the sensors during engine operation will result in the termination of injection and the shutting down the engine by the ECM. The loss of the signal from both of the sensors during start-up will prevent the engine from starting.Both sensors are magnetic sensors. The two sensors are not interchangeable. Do not switch the positions of the sensor. If the sensors are replaced, a timing calibration is NOT necessary for the engine. Timing calibration is only necessary after replacing an ECM that will not communicate.
Illustration 1 g00994866
C-10 and C-12 enginesLeft side engine view
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C-15 enginesLeft side engine viewIf 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 (Cat ET) and this feature is