Circuit DescriptionThe OEM truck manufacturer can install a permit switch in the dash or send an inhibit message via the J1939 data link to the engine ECM. The function of the inhibit message is to prevent the aftertreatment system from performing mobile regenerations. The purpose of this fault code is to inform the technician that the permit switch was disabled when Fault Code 1921, 1922, or 2639 was set active or when the system was requesting an active regeneration of the aftertreatment system. This fault code can indicate the reason that high aftertreatment soot load fault codes are logged.

Component LocationThe aftertreatment diesel particulate filter is located in the exhaust system and is installed by the original equipment manufacturer (OEM). The permit switch can be an actual switch in the vehicle dash or it can be a J1939 message sent via the J1939 data link. Refer to the OEM service manual.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault CodesThis fault code is triggered if the permit switch is disabled when Fault Code 1921, 1922, or 2639 is activated for high soot load levels in the diesel particulate filter or when the ECM is requesting active regeneration of the aftertreatment diesel particulate filter.

Action Taken When the Fault Code is ActiveThe ECM logs the fault code immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault CodeTo validate the repair, start the engine and let it idle for 1 minute with the permit switch enabled.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passesThe ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults.

Shop TalkIf this fault code is active and there has been damage to the aftertreatment system, the permit switch can possibly have prevented the aftertreatment system from performing a mobile (active) regeneration.

Consult with the OEM if the aftertreatment system has malfunctioned due to the permit switch.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Cause:1) ECM calibration