0303679 JOHNSON SCREW

Table 1
Diagnostic Codes Table
Code 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 OperationThe PWM sensors provide a signal to the engine's ECM. 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 8V 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 g01542213
Typical schematic
Illustration 2 g01234146
Location of ECM connectors
Illustration 3 g01572157
P1 ECM connector
(P1-11) Left exhaust temperature
(P1-12) Right exhaust temperature
(P1-60) Digital return
Illustration 4 g01572158
P2 ECM connector
(P2-55) Digital return
(P2-56) 8 V supply
(P2-57) 8 V supply
Illustration 5 g01094844
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal Test Step 1. Check for "Active" or "Logged" Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
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 -8 diagnostic code is active for one of the exhaust temperature sensors. 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.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, "Electrical Connectors - Inspect" 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
Turn the keyswitch to the OFF position.
Disconnect the suspect sensor(s) at the sensor connector.
Turn the keyswitch to the ON position.
Measure the voltage on the ECM side of the sensor connector between pin A and pin B for the suspect sensor(s). Expected Result:The supply voltage is 8.0 0.4 VDC.Results:
OK - The supply voltage is 8.0 0.4 VDC. Proceed to Test Step 4.
Not OK - The supply voltage is not 8.0 0.4 VDC. Proceed to Test Step 3.Test Step 3. Check the Digital Supply Voltage at the ECM
Turn the keyswitch to the OFF position.
Remove the supply wire from P1-56. Install a wire jumper into the socket for P1-56.
Remove the supply wire from P1-57. Install a wire jumper into the socket for P1-57.
Turn the keyswitch to the ON position.
Measure the voltage between the wire jumper in terminal P1-56 and engine ground.
Measure the voltage between the wire jumper in terminal P1-57 and engine ground.
Turn the keyswitch to the OFF position.
Remove the wire jumper and reconnect all wires. Reconnect ECM connector J1/P1. Expected Result:The supply voltage is 8.0 0.4 VDC.Results:
OK - The supply voltage is 8.0 0.4 VDC. The supply voltage at the ECM is correct. There is a problem in the wiring between the ECM and the sensor connector.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOP
Not OK - The supply voltage is not 8.0 0.4 VDC. The voltage at the ECM is not correct.Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.STOPTest Step 4. Check the Digital Sensor's Signal Frequency and the Duty Cycle at the Sensor Connector
Turn the keyswitch to the OFF position.
Remove the suspect sensor's signal wire from pin C of the sensor connector.
Reconnect the suspect sensor connector.
Turn the keyswitch to the ON position.
Measure the frequency and the duty cycle between the sensor's signal wire and pin B of the suspect digital sensor at the sensor connector.
Turn the keyswitch to the OFF position.
Replace the sensor's signal wire and reconnect the sensor. Expected Result:The duty cycle is between 10 to 90 percent. The frequency reading is approximately 500 Hz.Results:
OK - The frequency and the duty cycle are correct. Proceed to Test Step 5.
Not OK - The frequency or the duty cycle is not correct.Repair: Replace the sensor. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor.STOPTest Step 5. Check the Sensor's Duty Cycle at the ECM
Remove the signal wire for the suspect sensor from ECM connector P1. Refer to Illustration 1 for the terminal locations for the ECM connector.
Turn the keyswitch to the ON position.
Measure the duty cycle between the sensor's signal wire and the sensor's return wire. Note: Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.
Turn the keyswitch to the OFF position. Expected Result:The duty cycle is between 10 to 90 percent.Results:
OK - The duty cycle is correct.Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "ECM - Replace".STOP