P149C

DTC P149C Diesel Exhaust Fluid (DEF) System Pressure Reduction Malfunction

Description

The DEF is drawn in from the DEF tank to the supply pump by operating an internal diaphragm type pump driven with the pump motor and it is sent to the DEF injector via the main filter and the pressure line. A pressurized excess DEF returns to the DEF tank via the branched backflow line within the supply pump housing. The DEF pressure sensor detects the DEF pressure in the backflow line between the main filter and the one-way valve. The DEF reverting valve switches the DEF flow direction based on the command from the DEF control module. When the reverting valve is commanded ON at the pressure reduction control or after run control, a reverse DEF flow direction is formed and the pump returns the DEF to the tank via the suction line. The DEF pressure should be fallen to nearly 0 psi (0 kPa) if the pressure reduction control or after run control is completed. The DEF control module detects this DTC if the DEF pressure does not fall to a specified pressure at the pressure reduction control or after run control.

Condition for Running the DTC

- The battery voltage is between 10 to 16 volts.
- The intake air temperature 1 is more than 19 °F (-7 °C).
- The DEF reverting valve is being commanded ON.
- The DEF injector is being commanded OFF.

Condition for Setting the DTC

- The DEF control module detects that the DEF pressure does not fall to 5.8 psi (40 kPa) or below during the pressure reduction control or after run control.

Action Taken When the DTC Sets

- Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type D.

Conditions for Clearing the DTC

- Refer to DTC Type Definitions for Conditions for Clearing the DTC - Type D.

Diagnostic Aids

Caution: Diesel Exhaust Fluid (DEF) is highly corrosive to electrical connectors and rubber used in electrical wiring. If any of these components come in contact with DEF, wash the area throughly with warm water and allow to completely dry before reconnection. Make a visual inspection for damage if the connection has been exposed to DEF.

- If an intermittent condition is suspected, refer to Intermittent Conditions in this section.
- A sticking DEF reverting valve at the normal DEF flow position will set this DTC.
- Cover on the DEF tank and the DEF supply pump must be attached for keeping them warm.
- A sticking DEF heater valve at the closed position that affects the DEF defrosting may set this DTC.
- Normal DEF Supply Pressure on the scan tool during the DEF supply pump operating is nearly 130 psi (900 kPa).
- A skewed DEF pressure sensor value sets this DTC. The DEF Supply Pressure on the scan tool should be fallen to nearly 0 psi (0 kPa) if the after run control is completed.

Circuit / System Testing DTC P149C