Series 50 – Section 2.20 Synchronous Reference Sensor

Section 2.20
Synchronous Reference Sensor

The Synchronous Reference Sensor (SRS) is an electronic component that is mounted to the rear of the gear case. See Figure "SRS Location " .‪

Figure 1. SRS Location

Note: The length of the SRS sensor element is 33.15-33.66 mm (1.305-1.325 in.).

The sensor portion of the SRS extends through a hole in the gear case, and is positioned very near the rear of the bull gear. A bolt, inserted through a hole in the SRS bracket, secures the SRS assembly to the gear case. The SRS connector is black in color. ‪

The SRS sends a signal to the ECM. This signal is generated by a raised metal pin on the rear of the bull gear. See Figure "Bull Gear " .‪

Figure 2. Bull Gear

The bull gear pin passes by the SRS as the number one piston reaches approximately 45° before Top-Dead-Center. This information is used by the ECM to determine engine speed.‪

Section 2.20.1
Repair or Replacement Synchronous Reference Sensor

The SRS is a non-serviceable item and is replaced as a unit. No adjustment is required.‪

Section 2.20.2
Removal of Synchronous Reference Sensor

Remove the SRS as follows: ‪

1. Disengage the locking tang on the SRS connector. Grasp the connector bodies and gently pull them apart.
2. Using a socket and long extension, remove the SRS bolt.
3. Remove the SRS by pulling it straight out of the gear case.

Section 2.20.3
Installation of Synchronous Reference Sensor

Install the SRS as follows: ‪

Note: The SRS is an electronic component. Use care upon installation.

1. The O-ring on the sensor may be coated with clean engine oil for ease of installation.
2. Insert the SRS into the gear case and index the hole in the bracket with the hole in the gear case.
3. Insert the SRS bolt and torque it to 30-38 N·m (22-28 lb·ft).
4. Plug the connectors together, making sure the locking tang clicks into place.
5. Turn the ignition to the "ON" position. If any diagnostic code other than 25 appears, refer to the DDEC II Troubleshooting Guide, 6SE489, or DDEC  III/IV Single ECM Troubleshooting Guide, 6SE497.