CLAMP 9M8867 - 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 signal abnormal 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 signal abnormal 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 sensorA digital supply voltage is routed to terminal A of each sensor connector. The sensor return is routed to terminal B of each sensor connector. The sensor signal is routed to terminal C of each sensor connector. The 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
Schematic for the pulse width modulated sensors
Illustration 2 g01228528
P1 ECM connector
(P1-4) 8 V supply
(P1-5) Digital return
(P1-11) Left exhaust temperature
(P1-12) Right exhaust temperature
Illustration 3 g01159881
Sensor connector
(Terminal A) Sensor supply
(Terminal B) Sensor return
(Terminal C) Signal
Illustration 4 g01228531
Location of the exhaust temperature sensors (typical right side and left side engine views)
(1) Right exhaust temperature sensor
(2) Left exhaust temperature sensor Test Step 1. Check for Active Diagnostic Codes
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 connector terminal.
Determine if one of the following diagnostic codes is active for one of the exhaust temperature sensors:
-3
-4Expected Result:No diagnostic codes are active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are active. There are no active diagnostic codes, but a problem with the sensor is still suspected. Proceed to Test Step 5.
Not OK - A -3 diagnostic code is active or the diagnostic code is logged several times. There is an open circuit or a short to the +Battery in one of the sensor circuits. Proceed to Test Step 2.
Not OK - A -4 diagnostic code is active or the diagnostic code is logged several times. A short to ground has been detected in one of the sensor circuits. Proceed to