3508, 3508B, 3508C, 3512, 3512B, 3512C, 3516, 3516B and 3516C Engines Caterpillar Monitoring System Caterpillar

Illustration 1	g00573143
LH/RH Temperature Sender (Inlet Air)

Note: Ensure that the desired diagnostic code (CID FMI) is on hold. Ensure that the "SERV CODE" indicator is ON. Use the electrical system schematic for the engine that is being serviced to find the connector contact on the Main Display Module which corresponds to the CID that is currently shown.

This diagnostic code is recorded when the Main Display Module reads the voltage of the sender signal as being too low. The corresponding Gauge Needle is in the warning region as a result of this diagnostic condition. The following examples are possible causes.

• The inlet air temperature sender unit has a problem.

• The signal circuit for the inlet air temperature sender unit in the engine harness is shorted to ground.

• The Main Display Module has a problem.

Note: The Main Display Module is unable to determine when a sender or sender signal harness is open or the resistance is too high. This condition causes the corresponding Gauge Needle to stay at the left side of the scale.

1. Measure the Resistance of the Sender.

   1. Turn the "ECS" switch to the OFF/RESET position.

   2. Disconnect the engine harness from the inlet air temperature sender unit.

   3. Measure the resistance that is between the two contacts of the sender connector. The following table illustrates the correct approximate resistance at various temperatures.
      Show/hide table

      Table 1

      Approximate Resistances For The Sender Connector Contacts
      Temperature	Resistance
      25 ± 2°C (77 ± 3.6°F)	1000 Ohms
      100 ± 2°C (212 ± 3.6°F)	103.7 Ohms

2. Check the Display Area and the Harness.

   1. Turn the "ECS" switch to the OFF/RESET position.

   2. Check for loose connections or corroded connections to the inlet air temperature sender.

   3. Replace corroded contacts and tighten loose connections.

   4. Turn the "ECS" switch to the COOLDOWN/STOP position. The "SERV CODE" indicator should be ON for the diagnostic code CID 172 FMI 04.

   5. Disconnect the engine harness from the inlet air temperature sender unit. Observe the "SERV CODE" indicator.

      Expected Result: The "SERV CODE" indicator should turn OFF.

      Results:

      • OK - The "SERV CODE" indicator turns OFF. The inlet air temperature sender unit has a problem. Replace the inlet air temperature sender unit.

      • Not OK - The SERV CODE indicator stays ON. The harness wiring or the Main Display Module has a problem. Proceed to Step 3.

3. Check the Sender Wire for a Short to Ground.

   1. Turn the "ECS" switch to the OFF/RESET position.

   2. Disconnect the engine harness from the inlet air temperature sender unit.

   3. Turn the "ECS" switch to the COOLDOWN/STOP position.

   4. Measure the voltage of the harness signal wire from the inlet air temperature sender unit. The voltage should be measured from pin 1 to pin 2 (ground).

      Expected Result: The voltage should be 6.0 ± 0.5 DCV.

      Results:

      • OK - The voltage is 6.0 ± 0.5 DCV. The voltage is correct. If the SERV CODE indicator is still ON, repeat Step 1 through Step 3. If the cause of the diagnostic fault is not found, replace the Main Display Module.

      • Not OK - If the voltage is less than 0.5 DCV, the harness wiring has a problem. There is an open circuit, a short to ground in the inlet air temperature sender wire or a poor connection to a connector. Repair the harness or replace the harness. If the cause of the diagnostic fault is not found, replace the Main Display Module.

      • Not OK - If the voltage is not greater than 6.5 DCV or the voltage is not less than 0.5 DCV, the harness is shorted to a power circuit. Repair the harness or replace the harness. If the cause of the diagnostic fault is not found, then replace the Main Display Module.