RENR5042-02 135 Troubleshooting Section 342-08 Secondary Engine Speed signal abnormal 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. The engine uses two engine speed/timing sensors.
The primary engine speed/timing sensor detects the unique pattern of crankshaft gear and the secondary engine speed/timing sensor picks up the unique pattern of the camshaft gear. Both of the engine speed/timing sensors detect the reference for engine speed and timing from a unique pattern on the gear. The Engine Control Module (ECM) measures the time between the pulses that are created by the sensors as the gears rotate in order to determine rpm. Complete all of the following tasks when you install a speed/timing sensor: 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. Lubricate the O-ring with oil. Ensure that the sensor has a face seal inside the connector body. If a seal is damaged or missing, replace the seal. Ensure that the sensor is fully seated into the engine before tightening the bracket bolt. 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: Ensure that the connector is latched on both sides.
Ensure that the harness is properly secured, and ensure that the tie-wraps are placed in the correct location. 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. 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.