Overview
| CODE | REASON | EFFECT |
| Fault Code: 6786 PID: SPN: 3610 FMI: 2/20 LAMP: None SRT: |
An offset in the Diesel Particulate Filter Outlet Pressure Sensor reading has been detected.
|
Possible reduced engine performance. |
Circuit Description
The engine control module (ECM) provides a 5 volt supply to the aftertreatment diesel particulate filter outlet pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The aftertreatment diesel particulate filter outlet pressure sensor provides a signal to the ECM on the aftertreatment diesel particulate filter outlet pressure sensor signal circuit. This sensor signal voltage changes based on the pressure at the outlet of the aftertreatment diesel particulate filter.
Component Location
The aftertreatment diesel particulate filter differential pressure sensor is mounted on the diesel particulate filter. It is a combination sensor that detects both diesel particulate filter differential pressure and outlet pressure. Refer to the original equipment manufacturer (OEM) service manual.
Conditions for Running the Diagnostics
This diagnostic consists of two parts:
One part runs when the keyswitch is initially turned ON before the engine is started
The second part runs continuously while the engine is running.
Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the aftertreatment diesel particulate filter outlet pressure was greater than 1.5 kpa [0.22 psi] or less than -1.5 kpa [0.22 psi] at initial key ON, or was not changing with engine conditions.
Action Taken When the Fault Code is Active
- The ECM illuminates the amber CHECK ENGINE lamp and/or malfunction indicator lamp (MIL) after the diagnostic fails on two consecutive trips.
- Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Conditions for Clearing the Fault Code
- To validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop and go city type driving and steady state highway type driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.
- To validate the repair using a Chassis Dynamometer, utilize a routine that incorporates acceleration and motoring events, steady state highway type operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.
- Turn the key switch OFF and allow the ECM to completely powerdown.
- To validate the repair, perform a key cycle and leave the key in the ON position for 2 minutes. Then start the engine and let it idle for 1 minute.
- The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
- The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
- For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
- The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.
Shop Talk
Possible causes of this fault code include:
Stuck in-range aftertreatment diesel particulate filter outlet pressure sensor reading
High resistance in the aftertreatment diesel particulate filter outlet pressure sensor signal or return wires
Higher than expected diesel particulate filter outlet pressure
Excessive diesel exhaust fluid (DEF) deposits in the aftertreatment decomposition tube
Plugged aftertreatment outlet pressure sensor ports could cause this fault code if pressure is held in the port after the engine is turned OFF.
Frozen, plugged, or restricted aftertreatment DPF differential pressure sensor tubes.
Note: It is possible to set this fault in a shop environment by performing a key cycle with the tailpipe connected to an exhaust ventilation system.
- Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.
Troubleshooting Summary
- Check for primary fault codes
- Technical Service Bulletin is available
- Damaged or missing aftertreatment DPF differential pressure sensor tubes
- Aftertreatment DPF differential pressure sensor stuck in-range
- High exhaust restriction
- Aftertreatment DPF outlet pressure sensor open circuit check
- Aftertreatment DPF outlet pressure circuit pin to ground short
- Deposits in the SCR decomposition tube
- Leaks in the aftertreatment diesel exhaust fluid dosing system
- Aftertreatment DPF Outlet Pressure Sensor wire pin to pin short circuit check
- ECM calibration revision history check
- Aftertreatment DPF differential pressure sensor is malfunctioning
Solution: S00000422
Verification
Conditions
- Turn keyswitch ON.
- Connect the recommended Cummins® electronic service tool or equivalent.
Action
- Use the recommended Cummins® electronic service tool or equivalent to read the fault codes.
Specification
Before troubleshooting this fault code, troubleshoot any fault code that is active or has more than one inactive count within the last 25 engine operating hours from the following list:
- Aftertreatment DPF: 3133, 3134, 3135
Linked Solutions
- None
Repair
- Perform a search on the appropriate fault codes.
Validation
- None
Solution: S00011076
Verification
Conditions
- Turn keyswitch OFF.
Specification
- Proceed to the Repair section if the Technical Service Bulletin is applicable.
Linked Solutions
- None
Repair
- Complete the action outlined in the Technical Service Bulletin.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00010099
Verification
Conditions
- Turn keyswitch OFF.
Action
- Visually inspect the aftertreatment differential pressure tubes for proper installation.
- Inspect the aftertreatment DPF differential pressure sensor tubes for signs of damage, plugging, kinks, leakage or loose connections.
In extreme cold ambient temperatures it is important to check for a frozen, plugged, or restricted aftertreatment DPF differential pressure sensor tubes. Ice can form in the aftertreatment DPF differential pressure sensor tubes causing obstruction/sticking and may not be present at the time of troubleshooting.
Specification
- If damage, kinks or blockages are found, then proceed to the Repair section.
Linked Solutions
- None
Validation
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
Solution: S00000793
Verification
Conditions
- Turn keyswitch ON.
- Connect the recommended Cummins® electronic service tool or equivalent.
Action
- Use the recommended Cummins® electronic service tool or equivalent.
- Monitor the aftertreatment DPF differential pressure sensor voltage.
Specification
- If the aftertreatment DPF differential pressure sensor voltage readings are not within specification, then a malfunctioning aftertreatment DPF differential pressure sensor has been detected.
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00009950
Verification
Conditions
- Turn keyswitch OFF.
Specification
- If the exhaust restriction is not within specification, then a restriction in the exhaust has been detected.
Linked Solutions
- None
Repair
Repair or replace only the components that were found to be out of specification.
- Repair the source of the exhaust restriction.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00003179
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the OEM wiring harness connector from the ECM.
- Disconnect the aftertreatment DPF differential/outlet pressure sensor from the OEM wiring harness.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the OEM wiring harness ECM connector aftertreatment DPF outlet pressure sensor SIGNAL pin and the OEM wiring harness aftertreatment DPF outlet pressure sensor connector SIGNAL pin.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning OEM wiring harness has been detected if the resistance is greater than the following specification: 10 Ω
Linked Solutions
- None
Repair
- Troubleshoot each harness connected in series to determine which contains the open circuit.
- Repair or replace the OEM wiring harness.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00002790
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the aftertreatment DPF differential/outlet pressure sensor from the OEM wiring harness.
- Disconnect the OEM wiring harness connector from the ECM.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the aftertreatment DPF outlet pressure sensor SIGNAL pin in the OEM wiring harness ECM connector and ground.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning OEM wiring harness has been detected if the resistance is less than the following specification: 100k Ω
Linked Solutions
- None
Repair
- Troubleshoot the OEM wiring harness, and all interconnects.
- Repair or replace the OEM wiring harness.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00000564
Verification
Conditions
- Turn keyswitch OFF.
Specification
- If any excessive aftertreatment diesel exhaust fluid deposits were found inside the decomposition tube, then a plugged or restricted aftertreatment decomposition tube has been detected.
- Proceed to Linked Solutions section for additional checks.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00000735
Verification
Conditions
- Turn keyswitch OFF.
- Reconnect all aftertreatment diesel exhaust fluid lines and electrical connectors to the dosing unit and aftertreatment diesel exhaust fluid tank if they have been previously disconnected during troubleshooting.
Action
- Remove the aftertreatment diesel exhaust fluid dosing valve.
- Perform the Aftertreatment Diesel Exhaust Fluid System Leak Test found under ECM Diagnostic Tests.
Specification
- If a line, fitting, connection, or dosing unit is leaking, then a malfunction has been detected in the aftertreatment diesel exhaust fluid system or dosing unit.
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00001105
Verification
Conditions
- Turn keyswitch OFF.
- Disconnect the aftertreatment DPF outlet pressure sensor from the OEM wiring harness.
- Disconnect the OEM wiring harness connector from the ECM.
Action
- Inspect the pins and connectors for damage.
- Measure the resistance between the aftertreatment DPF outlet pressure sensor SIGNAL pin in the OEM wiring harness ECM connector and all other pins in the OEM wiring harness ECM connector.
- Refer to the circuit diagram or wiring diagram for connector pin identification.
Specification
- A malfunctioning OEM wiring harness has been detected if the resistance is less than the following specification: 100k Ω
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00000443
Verification
Conditions
- Connect all components.
- Turn keyswitch ON.
- Connect the recommended Cummins® electronic service tool or equivalent.
Action
- Use the recommended Cummins® electronic service tool or equivalent to read the fault codes.
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revision listed in the ECM calibration revision history for applicable changes.
Specification
- If a calibration update for this fault code is available, the ECM calibration revision must be that revision or higher.
Linked Solutions
- None
Repair
- Prior to downloading the ECM calibration, check to see that all job images and all other troubleshooting has been documented as downloading an ECM calibration will remove the fault codes on the ECM.
- Download the updated ECM calibration code.
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
Solution: S00010942
Verification
Conditions
- Turn keyswitch OFF.
Action
- Verify all preceding solution verifications for this fault code have been performed.
Specification
- If the fault code is still active after all preceding solution verifications have been performed, then a malfunctioning aftertreatment DPF differential pressure sensor has been detected.
Linked Solutions
- None
Validation
- Connect all components
- Connect the recommended Cummins® electronic service tool or equivalent.
- Disable the fault code.
- Operate the engine within the “Conditions for Clearing the Fault Code” found in the Overview section of the troubleshooting procedure.
- Verify that the fault code is no longer active.
- Check ECM Calibration Revision History
- Use the recommended Cummins® electronic service tool or equivalent to find the current ECM code and revision number in the ECM.
- Compare the ECM code and revision number in the ECM to the calibration revisions listed in the ECM Calibration Revision History Database for applicable changes related to this fault code.
- Refer to ECM Calibration Revision History Database.
If all steps have been completed and no root cause has been identified, then follow the technical escalation process.