OIL COOLER AND LINES 1357989 - Caterpillar

System Operation Description:Use this procedure to troubleshoot a suspected problem with the speed/timing sensor circuit. Also use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
145-3 12 Volt DC Power Supply : Voltage Above Normal The 12 V power supply is above normal for two seconds. The code is logged.
The alarm output is activated.
The shutdown output is activated.
The engine is shut down.
145-4 12 Volt DC Power Supply : Voltage Below Normal The 12 V power supply is below normal for two seconds.
320-3 Speed/Timing Sensor short to +batt Engine speed is greater than 280 rpm, the Electronic Control Module (ECM) has lost the signal for the timing gear pattern for 1.3 seconds.
320-8 Engine Speed/Timing signal abnormal Engine speed is greater than 280 rpm, the ECM has detected an invalid signal for the timing gear pattern and a valid timing signal returns within one second. The speed/timing sensor provides information about engine speed and the position of the crankshaft to the engine ECM. The sensor is powered by the sensor supply (12 VDC) from the ECM. A magnetic pickup is located in the pickup head of the sensor. The timing ring is mounted on the rear of the left camshaft. As the teeth of the ring rotate past the sensor pickup head, the sensor generates a signal that matches the pattern of the teeth.With the information from the engine speed/timing sensor, the ECM is able to calculate the positions of the pistons in the cylinders. The ECM determines the desired ignition timing according to the engine speed and load. If detonation is detected in any of the cylinders, the ECM retards the timing of the affected cylinders. The ECM sends voltage pulses to the ignition transformers for firing the spark plugs according to the desired timing.During engine operation, the ECM will shut down the engine if a problem is detected with the signal from the speed/timing sensor. The ECM activates the corresponding diagnostic code.The ECM will not initiate ignition if there is a problem with the speed/timing sensor. The engine will not start. Unless the engine speed exceeds 280 rpm, the corresponding diagnostic code will not be activated. Poor electrical connection or a problem in a wiring harness can cause diagnostic codes. The next likely cause is a problem with the engine speed/timing sensor. The least likely cause is a problem with the ECM.
Illustration 1 g01725773Schematic of the circuit for the engine speed/timing sensor
Illustration 2 g03086936
Schematic of the engine speed/timing sensor. 20 cylinder engines only.
Test Step 1. Inspect the Electrical Connectors and the Wiring
Set the engine control switch to the OFF/RESET position. Remove the electrical power from the engine.