GEAR 8R4480 - Caterpillar

Conditions Which Generate This Code:
Illustration 1 g01262239
Schematic of the transmission output speed sensor 2This diagnostic trouble code is associated with the transmission output speed sensor 2. The FMI 8 means that the ECU has determined that the signal frequency is not within the expected range. This sensor is a frequency sensor. The sensor sends a frequency to the ECU as the gear teeth pass the magnet. The voltage is proportional to the speed of the transmission output shaft. The frequency that is sent to the ECU increases when the speed of the teeth increases. The possible causes of this diagnostic trouble code are listed below:
Intermittent connections or poor connections
The sensor is loose.
The sensor has failed.
The ECU has failed. This is unlikely.Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear the diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of SPN 3825 FMI 8 is active before performing this procedure. The engine must be running in order for the diagnostic trouble code to be active.Note: Use a digital multimeter for the measurements in this procedure. System Response:The ECU will use the other speed sensor in order to determine the speed of the transmission output shaft.Test Step 1. INSPECT THE HARNESS CONNECTIONS.
Turn the disconnect switch to the OFF position.
Inspect all harness connections that are related to the sensor. Make sure that the connectors are clean and tight.
Check the connectors for proper mating. Ensure that all the seals are present and in place.
Check the harness for signs of damage or abrasion.
Check the wires at the connector. Ensure that the wires are secured tightly into the connector.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit. Take care not to pull the wire out of the connector.
Check the exposed wires at the connectors for nicks or signs of abrasion.
Check for moisture inside the connector.
Check the connectors for dirty contacts or corroded contacts.
Check each pin and each socket of the machine harness connectors. Ensure that the contacts are properly installed. The contacts should mate correctly when the two pieces of the connector are placed together.Expected Result: