ROD AS 4220080 - Caterpillar

Table 1
J1939 Code and Description CDL Code and Description Comments
6797-7
Aftertreatment #1 SCR Intake Absolute Pressure : Not Responding Properly 4054-7
Aftertreatment #1 DEF Doser #1 Pressure Not Responding To Command The Selective Catalyst Reduction (SCR) Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #1.
6797-17
Aftertreatment #1 SCR Intake Absolute Pressure : Low - least severe (1) E1637 (1)
Low Aftertreatment #1 SCR Catalyst Intake Pressure The SCR Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #1.
6798-7
Aftertreatment #2 SCR Intake Absolute Pressure : Not Responding Properly 4055-7
Aftertreatment #2 DEF Doser #1 Pressure Not Responding To Command The Selective Catalyst Reduction (SCR) Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #2.
6798-17
Aftertreatment #2 SCR Intake Absolute Pressure : Low - least severe (1) E1638 (1)
Low Aftertreatment #2 SCR Catalyst Intake Pressure The SCR Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #2. Probable Causes
Codes
Sensor
Debris
Voltage
Exhaust systemRecommended Actions
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Look for active codes that are associated with the system for the event code.
Codes
Result: An associated code is active.
Repair: Troubleshoot any associated codes before continuing with this test.
Result: A code is active or logged.
Proceed to Test Step 2.
2. Verify that the Selective Catalyst Reduction (SCR) Inlet Pressure Sensor is Installed
A. Turn the keyswitch to the OFF position.
B. Visually inspect the exhaust system to ensure that the SCR catalyst inlet pressure sensor has not been tampered with or removed.
Sensor
Result: The SCR catalyst inlet pressure sensor is installed in the exhaust system.
Proceed to Test Step 3.
Result: The SCR catalyst inlet pressure sensor is not installed in the exhaust system.
Repair: Install the SCR catalyst inlet pressure sensor into the exhaust system.
If the problem is not resolved, proceed to Test Step 3.
3. Check the SCR Catalyst Inlet Pressure Sensor Port for Debris
A. Turn the keyswitch to the OFF position.
B. Visually inspect the SCR catalyst inlet pressure sensor for debris.
C. Visually inspect the SCR catalyst inlet pressure sensor port for blockage by debris.
Debris
Result: The SCR catalyst inlet pressure sensor port is not blocked by debris.
Proceed to Test Step 4.
Result: The SCR catalyst inlet pressure sensor port is blocked by debris.
Repair: Clear the debris from the SCR catalyst inlet pressure sensor port and replace the affected sensor.
If the problem is not resolved, proceed to Test Step 6.
4. Check the Supply Voltage to the SCR Catalyst Inlet Pressure Sensor
A. Turn the keyswitch to the OFF position.
B. Disconnect the SCR catalyst inlet pressure sensor from the wiring harness connector.
C. Measure the voltage between the following pins of the wiring harness connector:
- Pin 1 and Pin 2
5 VDC
Result: There was 5 VDC present between pin 1 and pin 2.
Proceed to Test Step 4.
Result: There was not 5 VDC present between pin 1 and pin 2.
Repair: There is a problem with the supply voltage to the sensor. Determine the cause of the supply voltage issue. Refer to Troubleshooting, Sensory Supply - Test for additional