RING 8D9746 - Caterpillar

Table 1
Transmission ECM (MID 81)
DTC Code Description System Response
177-3 Transmission Oil Temperature Sensor : Voltage Above Normal A transmission oil temperature indicator is lit on the display.
177-4 Transmission Oil Temperature Sensor : Voltage Below Normal A transmission oil temperature indicator is lit on the display. Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.Possible Causes for an FMI 3 Diagnostic code are:
The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the +battery.
The sensor has failed.
The ECM has failed. This condition is unlikely.Possible Causes for an FMI 4 Diagnostic code are:
The sensor has failed
The signal circuit for the sensor is shorted to ground
The ECM has failed. A failure of the Transmission ECM is unlikely.
Illustration 1 g03489776
Schematic of the Transmission Oil Temperature Sensor
The table below is a reference that can be used when checking the resistance of the temperature sensors listed in the table above.
Table 2
CELSIUS TEMPERATURE FAHRENHEIT TEMPERATURE RESISTANCE
10 50 1991.4
15 59 1571.9
20 68 1249.5
25 77 1000
30 86 805.5 Note: The diagram above is a simplified schematics of the Transmission ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR3118 for the complete schematic.
Table 3
Troubleshooting Test Steps Values Results
1. Identify The Active DTC Code Associated With The Suspect Circuit
Code present. FMI 3 diagnostic code, proceed to Test Step 2.
FMI 4 diagnostic code, proceed to Test Step 5.
Begin Process For FMI 3 Troubleshooting HERE
2. Check The Sensor
Note: See Table 2 for a list of resistances related to specific temperature values. The maximum resistance for the sensor is 33,650 Ω, the minimum is 51.2 Ω.
A. Turn the key start switch and the disconnect switch to the OFF position.
B. Disconnect the sensor from the harness.
C. Measure the resistance between pin 1 and 2 of the sensor.
The resistance reading agrees with the values from Table 2. OK - The resistance reading agrees with the values in 2.
Proceed to Test Step 3.
NOT OK - The resistance reading does not agree with the values in 2.
Repair: Replace the sensor.
STOP
3. Check For An Open In The Sensor Circuit
A. The key start switch and disconnect switch remain in the OFF position.
B. The harness connector remains disconnected from the sensor.
C. Disconnect the J1 and J2 connectors from the ECM.
D. At the harness connector for the sensor install a jumper wire.
E. At the harness connector for the ECM measure the resistance at the contacts for the sensor.
The resistance reading is less than 5 Ω. OK - The resistance is less than 5 Ω.
Proceed to Test Step 4.
NOT OK - The resistance is greater than 5 Ω.
Repair: Either the