GASKET 4K4938 - Caterpillar

Use this procedure to troubleshoot a problem with the exhaust temperature sensors. Also, use this procedure if the following diagnostic code is active or easily repeated.
Table 1
Diagnostic Codes Table
J1939 Code and Description Conditions which Generate this Code System Response
173-9
Engine Exhaust Gas Temperature : Abnormal Update Rate The Integrated Sensor Module (ISM) has not received several messages that were expected from the exhaust temperature sensors over the CAN data link. The code is logged.
The alarm output is activated. The ISM is an electronic monitoring system used to monitor exhaust temperatures. The module monitors the following thermocouples:
Thermocouple for the exhaust port of each cylinderThe ISM reads each of these temperatures and sends this information via the CAN data link to the ECM and the optional remote control panel.If the ECM cannot communicate with the ISM, the ECM activates a diagnostic code related to identify the problem. The most likely cause of the diagnostic code is a problem with an electrical connector or a harness. The next likely cause is a problem with the ISM.Terminating resistors must be connected to each end of the CAN data link. The terminating resistors improve the communication signal between the devices. If there is an intermittent diagnostic code for any of the devices connected to the CAN data link, check the terminating resistors. One of the terminating resistors is in the control panel. The other terminating resistor is inside the ECM control box. If the engine is not equipped with a remote panel, the other terminating resistor will be connected at the far end of interconnect harness. Refer to Troubleshooting, "CAN Data Link - Test" for details related to troubleshooting the data link circuit.This troubleshooting procedure may generate additional diagnostic codes. Correct the cause of the original diagnostic code before continuing. You clear the diagnostic codes after the problem is resolved.
Illustration 1 g03818797
Illustration 2 g03382427
(1) ISM P1/J1
(2) ISM P2/J2
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Determine if a code is active or logged.
Codes
Result: A 173-9 code is active or logged.
Repair: The ECM has detected a problem with the communication between the ECM and the sensor.
Proceed to Test Step 3.
Result: A code is not active or logged.
Proceed to Test Step 2.
2. Inspect the Electrical Connectors and the Wiring
A. Ensure that the electrical power has been removed