HOSE 2040951 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the exhaust temperature sensors or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
827-8 Left Exhaust Temperature Sensor abnormal frequency, pulse width, or period     The Electronic Control Module (ECM) detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz.
The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent.     The value of the parameter is set to zero.
The code is logged.    
828-8 Right Exhaust Temperature Sensor abnormal frequency, pulse width, or period     The ECM detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz.
The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent.    System OperationUse this procedure to troubleshoot any suspect problems with the following sensors:
Left exhaust temperature sensor
Right exhaust temperature sensorThe PWM sensors provide a signal to the engine's ECM for certain engine operating conditions. The sensors receive a 8.0 0.4 VDC regulated voltage from the ECM.The sensor's wires are routed from the ECM to the sensor connectors. The following list gives the terminal locations for the sensor connector.
Terminal A 8 V supply
Terminal B sensor return
Terminal C sensor signalThe ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.
Illustration 1 g01213936
Typical schematic
Illustration 2 g01213937
P1 ECM connector (P1-4) 8 V supply (P1-5) Digital return (P1-11) Left exhaust temperature (P1-12) Right exhaust temperature
Illustration 3 g01094844
Sensor connector (Pin A) Sensor supply (Pin B) Sensor return (Pin C) Signal
Illustration 4 g01215186
Left side view (1) Left exhaust temperature sensor
Illustration 5 g01215187
Right side view (2) Right exhaust temperature sensorTest Step 1. Check for an "Active" Diagnostic Code
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a diagnostic code has occurred several times.Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal.
Determine if a -8 diagnostic code is active for one of the exhaust temperature sensors.Expected Result:No diagnostic code is active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are active.Repair: If the problem is intermittent, refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct procedures for inspecting electrical connectors.STOP
Not OK - A -8 diagnostic code is active or the diagnostic code is logged several times. Proceed to Test Step 2.Test Step 2. Check the Digital Supply Voltage at the Sensor Connector
Disconnect the suspect sensor(s)