Caterpiller C27 & C32 Engine Speed/Timing Sensor Circuit - Testby Dave Jack Auto Car Repair Knowledge
This instruction show you guide on how to do speed/timing sensor test for CAT C27 and CAT C32 engine.
SMCS Code: 1439-038-VF; 1912-038
System Operation Description:
Use this procedure to troubleshoot any suspect problems with the following sensors:
• Primary engine speed/timing sensor
• Secondary engine speed/timing sensor
This procedure covers the following diagnostic codes:
• 190-08 Engine Speed abnormal
• 342-08 Secondary Engine Speed signal abnormal
The engine uses two engine speed/timing sensors.
The primary engine speed/timing sensor detects the reference for engine speed and timing from a timing ring with a notched pattern that has been machined onto a portion of the crankshaft gear. The signal from the primary engine speed/timing sensor is also used by the ECM as a control reference during a timing calibration.
secondary engine speed/timing sensor detects the reference for engine
speed and timing from a timing ring with a notched pattern that has been
machined onto a portion of the camshaft gear.
Control Module (ECM) counts the time between pulses that is created by
the sensor as each gear rotates in order to determine rpm. Timing is
provided by the unique pattern of notches in the timing ring.
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
2020 Cat ET diagnostic software Free Download
A timing calibration is necessary after the ECM software has been updated. Refer to
Troubleshooting, “Engine Speed/Timing Sensor - Calibrate” for information that is related to timing calibration.
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
• 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.
Created on Oct 22nd 2020 20:31. Viewed 42 times.