P1491

DTC P1491 Diesel Exhaust Fluid (DEF) Injection Pressure Too High

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 pressure is kept near constant pressure and it is regulated by speed of the DEF supply pump motor dependant upon values from the DEF pressure sensor. The DEF pressure should be stay nearly 130 psi (900kPa) if the DEF supply pump motor is energized. The DEF control module detects this DTC if the DEF pressure went excessively high for certain length of time.

Condition for Running the DTC

- The battery voltage is between 10 to 16 volts.
- The ignition switch is ON.
- The intake air temperature 1 is more than 19 °F (-7 °C).
- The exhaust gas temperature (EGT) 3 is more than 374 °F (190 °C).
- The DEF injection control is commanded ON.

Condition for Setting the DTC

- The DEF control module detects that the DEF pressure is more than 181 psi (1250 kPa) for longer than 5 seconds.

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.
- 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 P1491