The following procedure contains troubleshooting steps and information regarding the aftertreatment system.
NOTE: The information in this procedure only applies to rear gear train engines.
Leaks in the exhaust system can cause exhaust odor or white smoke.
Inspect the exhaust piping for leaks, cracks, and loose connections. Refer to Procedure 010-024 in Section 10.
Tighten the exhaust clamps, if necessary. Refer to the OEM service manual for the correct torque value.
It may be necessary to perform a stationary (parked) regeneration to locate exhaust leaks. Refer to Procedure
014-013 in Section 14.
The ambient temperature affects the length of time it will take to perform a stationary (parked) regeneration,
because the engine must work harder to increase the exhaust temperatures to the appropriate levels in cold ambient temperatures.
In cold ambient temperatures (approximately -18°C [0°F] or colder), stationary (parked) regeneration may take
longer to complete. In extremely cold ambient temperatures, stationary (parked) regeneration may not complete.
In these cases, it may be necessary to warm the engine to operating temperature before starting the stationary
(parked) regeneration, or to move the vehicle to a location with higher ambient temperatures.
The vehicle manufacturer has the option of installing two switches that control the aftertreatment function: the start
switch and the permit switch.
The start switch (called the Diesel Particulate Filter Regeneration Start Switch in INSITE electronic service tool)
is used to start a stationary (parked) regeneration. The vehicle manufacturer may also reference this switch as a “stationary regeneration switch”, “start switch”, or “parked regeneration switch”.
The permit switch (called the Diesel Particulate Filter Permit Switch in INSITET electronic service tool) is used to allow the operator to disable active regeneration, if necessary. The vehicle manufacturer may also reference this switch as an “inhibit switch”, “stop switch”, or “disable switch”.
The start switch can be hardwired to the ECM, or it can be multiplexed over J1939 multiplexing.
If the start switch is hardwired, it shares an ECM pin with the diagnostic switch. When the switch is turned ON and the engine is OFF, the ECM interprets this signal as the diagnostic switch. When the switch is turned ON and the
engine is operating, the ECM interprets this signal as the start switch.
If the start switch is J1939-multiplexed, the signal for this switch is broadcast over the J1939 data link.
A J1939-multiplexed start switch signal has priority over a hardwired start switch signal. Therefore, if the start switch is enabled over J1939, the hardwired signal is ignored by the engine ECM.
The default setting for the start switch is “enabled”. If the start switch is enabled in INSITE electronic service tool, but no switch is installed (either hardwired or J1939-multiplexed), the switch status will remain OFF.
The position of the start switch can be monitored with INSITET electronic service tool in the data monitor/logger screen.
The permit switch can be hardwired to the ECM, or it can be multiplexed over J1939 multiplexing.
A J1939-multiplexed permit switch signal has priority over a hardwired start switch signal, so if the permit switch is enabled over J 1939, the hardwired signal is ignored by the engine ECM.
The position of the permit switch can be monitored with INSITETM electronic service tool in the Data Monitor/Logger screen:
• When the permit switch is ON, active regeneration is allowed.
• When the permit switch is OFF, active regeneration is not allowed.
The default setting for the permit switch is “enabled”. If the permit switch is enabled in INSITE electronic service tool, but no switch is installed (either hardwired or J1939- multiplexed), the switch status will remain OFF.
If the vehicle is operated for an extended period of time with the permit switch OFF, fault codes for the above normal levels of aftertreatment diesel particulate filter soot load or aftertreatment diesel particulate filter (DPF) system timeout can result (Fault Codes 1921, 1922, 2639, and 3753).
If the aftertreatment DPF soot load reaches the least severe level (Fault Code 2639), and the permit switch is OFF, the ECM will also log a Fault Code 2777.
If the aftertreatment exhaust gas temperature sensors are not connected properly, or if the wiring in the harness
between the engine and aftertreatment is not correct, the engine may experience frequent DPF lamp illuminations,
or stationary (parked) regenerations that do not complete.
Inspect the exhaust aftertreatment temperature sensor connectors to verify they are connected to the correct
connector on the aftertreatment system wiring harness.
Two of the temperature sensors have identical wiring harness connectors. Because the sensors are the same
part number, it is possible to install the wiring harness connectors to the wrong sensors.
To verify the correct sensor locations, use INSITE’M electronic service tool to monitor the following parameters
with the ignition key ON , but with the engine not running.
• Aftertreatment Diesel Oxidation Catalyst Inlet
Temperature Sensor Signal Voltage (V)
• Aftertreatment Diesel Particulate Filter Inlet
Temperature Sensor Signal Voltage (V)
• Aftertreatment Diesel Particulate Filter Outlet
Temperature Sensor Signal Voltage (V).
Unplug each of the aftertreatment exhaust gas temperature sensors, one at a time.
If the voltage changes when the sensor is unplugged, the wiring harness connector is connected to the correct sensor.
If the voltage does not change when the sensor is unplugged, switch the connector location to the other temperature sensor, unplug it, and check for a voltage change.
An incorrectly assembled aftertreatment wiring harness can not be checked by unplugging each of the aftertreatment exhaust gas temperature sensors.
The only method to check for a misassembled aftertreatment wiring harness is to check the wiring harness connectors for correct pin installation. Refer to the engine wiring diagram for connector pin identification and location.
When performing a stationary (parked) regeneration, monitor the exhaust temperatures in the aftertreatment system to determine why a stationary (parked) regeneration will not complete.
Possible causes for stationary (parked) regenerations that will not complete include:
• Misassembled aftertreatment wiring harness
• Aftertreatment exhaust gas temperature sensors installed in the wrong locations
• A plugged aftertreatment diesel oxidation catalyst
• A malfunctioning turbocharger
• Exhaust leaks between the engine and the aftertreatment
• Very low ambient temperatures (less than -18°C [0° F]).
A normal stationary (parked) regeneration will follow the pattern shown.
• The dashed line is for the aftertreatment diesel oxidation catalyst inlet temperature sensor.
• The dotted line is for the aftertreatment diesel particulate filter inlet temperature sensor.
• The solid line is for the aftertreatment diesel particulate filter outlet temperature sensor.
When the stationary (parked) regeneration begins (1 ), all three temperatures should be approximately the same,
and should increase at the same rate.
The wiring to the aftertreatment temperature sensors appears to be correct in this example, because they all read approximately the same temperature at the beginning of the stationary (parked) regeneration and increase at the same rate.
Aftertreatment injection begins when all three temperatures reach approximately 289°C [552°F] (2).
Once aftertreatment injection begins, the aftertreatment diesel oxidation catalyst inlet temperature may vary slightly, but will typically remain between 260 and 399°C [500 and 750°F].
The aftertreatment diesel particulate filter inlet and outlet temperatures will increase to approximately 482 to 649°C
[900 to 1200°F]. The temperatures may vary during the stationary (parked) regeneration, as the amount of fuel
injected during aftertreatment injection is changed to maintain a constant temperature.
The aftertreatment diesel particulate filter inlet and outlet temperatures will remain at this temperature for the
duration of the stationary (parked) regeneration.
This graph illustrates a stationary (parked) regeneration where the inlet of the aftertreatment diesel oxidation
catalyst is blocked.
• The dashed line is for the aftertreatment diesel oxidation catalyst inlet temperature sensor.
• The dotted line is for the aftertreatment diesel particulate filter inlet temperature sensor.
• The solid line is for the aftertreatment diesel particulate filter outlet temperature sensor.
In this condition, the engine speed will increase to the stationary (parked) regeneration speed of 1 000 to 11 00 rpm.
Raising the aftertreatment temperature to the aftertreatment injection temperature may take longer to complete than normal if the inlet to the aftertreatment diesel oxidation catalyst is plugged, restricting some of the exhaust flow.
Once aftertreatment injection begins (2), the aftertreatment diesel particulate filter inlet and outlet temperatures will differ greatly due to the plugged aftertreatment diesel oxidation catalyst being unable to oxidize the injected fuel. The aftertreatment diesel particulate filter has some capability to oxidize the injected fuel, but can not maintain this condition without damaging the filter material over time. It is possible that white smoke would be present from the vehicle tailpipe in this condition.
The wiring to the aftertreatment temperature sensors appears to be correct in this example, because they all
read approximately the same temperature at the beginning of the stationary (parked) regeneration and they
increase at the same rate.
This graph illustrates a stationary (parked) regeneration where the engine can not build enough heat to start
aftertreatment injection.
• The dashed line is for the aftertreatment diesel oxidation catalyst inlet temperature sensor.
• The dotted line is for the aftertreatment diesel particulate filter inlet temperature sensor.
• The solid line is for the aftertreatment diesel particulate filter outlet temperature sensor.
The engine speed will likely increase to the stationary (parked) regeneration speed of 1000 to 11 00 rpm, but
because the aftertreatment temperatures do not increase enough to start aftertreatment injection, the stationary
(parked) regeneration will not complete.
The wiring to the aftertreatment temperature sensor appears to be correct in this example, because they all
read approximately the same temperature for the same conditions.
Possible causes of this issue include:
• Low ambient temperatures. Move the vehicle to a location with higher ambient temperatures.
This graph illustrates a stationary (parked) regeneration where the wiring to the aftertreatment temperature
sensors is incorrect.
• The dashed line is for the aftertreatment diesel oxidation catalyst inlet temperature sensor.
• The dotted line is for the aftertreatment diesel particulate filter inlet temperature sensor .
• The solid line is for the aftertreatment diesel particulate filter outlet temperature sensor.
In this condition, the engine speed will increase to the stationary (parked) regeneration speed of 1 000 to 11 00 rpm.
Aftertreatment injection will not occur in this condition, because the aftertreatment diesel oxidation catalyst inlet
temperature does not reach the required temperature.
Because aftertreatment injection is not occurring, the aftertreatment temperatures should not read differently.
The possible cause of this condition is an incorrectly assembled aftertreatment wiring harness. See the aftertreatment exhaust gas temperature sensor wiring information in this procedure.
This graph illustrates a stationary (parked) regeneration where the connectors to the aftertreatment diesel
oxidation catalyst inlet temperature sensor and the aftertreatment diesel particulate filter outlet temperature sensor are reversed.
• The dashed line is for the aftertreatment diesel oxidation catalyst inlet temperature sensor.
• The dotted line is for the aftertreatment diesel particulate filter inlet temperature sensor.
• The solid line is for the aftertreatment diesel particulate filter outlet temperature sensor.
In this condition, the engine speed will increase to the stationary (parked) regeneration speed of 1000 to 11 00 rpm.
Aftertreatment injection may occur in this condition (2).
However, the aftertreatment diesel oxidation catalyst inlet temperature increases after aftertreatment injection
begins, while the aftertreatment diesel particulate filter outlet temperature remains constant.
The possible cause of this condition is that the connectors to the aftertreatment diesel oxidation catalyst inlet
temperature sensor and the aftertreatment diesel particulate filter outlet temperature sensor are reversed.
See the aftertreatment exhaust gas temperature sensor wiring information in this procedure.
