P1490

DTC P1490 Diesel Exhaust Fluid (DEF) System NOx Trap Low Efficiency

Description

The NOx sensor 1 is installed to the rear chamber of diesel particulate filter (DPF) housing and it measures the concentration of NOx in the exhaust gas from the engine at the upstream of SCR catalyst. The NOx sensor 2 is installed to the rear chamber of SCR catalyst housing and it measures the concentration of NOx in the exhaust gas after NOx conversion at the downstream of SCR catalyst. Each sensor element has a heater to maintain its active status. The measurement of NOx concentration in the exhaust gas is started after each NOx sensor status is valid, and the DEF control module switches to the DEF injection control based on actual measurement values of the NOx sensors. The DEF control module uses the modeled NOx concentration calculated from the current engine running conditions before each NOx sensor status is valid. The DEF control module receives NOx sensor information from the each NOx sensor control module via the controller area network (CAN) communication bus. If the DEF control module detects a low NOx conversion rate for a certain length of time, this DTC will set.

Condition for Running the DTC

- DTCs P2201, P2202, P2203, P2206, P2207, P2214, P2215, P2216, P2223, P2224, U029D and U029E are not set.
- DTCs P0016, P0027, P0079, P0080, P008F, P0090, P0091, P0092, P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0182, P0183, P0191, P0192, P0193, P0201, P0202, P0203, P0204, P0237, P0238, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P02E7, P02E8, P02E9, P0335, P0336, P0340, P0341, P0405, P0406, P042E, P046C, P0500, P0545, P0546, P0641, P0697, P111D, P111E, P2032, P2033, P2146, P2149, P2227, P2228, P2229, P2294, P2295 and P2296 are not set in the ECM. (3.0L 4JJ1)
- The battery voltage is between 10 to 16 volts.
- The ignition switch is ON.
- The engine is running.
- The intake air temperature 1 is more than 19 °F (-7 °C).
- The barometric pressure is greater than 11.3 psi (78 kPa).
- The diesel exhaust filter (DPF) regeneration is not running.
- The calculated SCR catalyst temperature is within a predetermined range.
- The calculated exhaust gas flow amount is within a predetermined range.
- The NOx sensor 1 and 2 status are valid.
- The NOx concentration on the sensor 1 is within a predetermined range.
- The DEF injection is commanded ON.

Condition for Setting the DTC

- The NOx conversion efficiency measured with each NOx sensor is lower than a predetermined range.

Action Taken When the DTC Sets

- The DEF control module requests the ECM to illuminate the MIL. Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type A.
- The DEF control module and the ECM apply defaulted warning actions and fail-safe controls. Refer to Default Action and Fail-Safe List.

Conditions for Clearing the DTC

- Refer to DTC Type Definitions for Conditions for Clearing the DTC - Type A or Type B.

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.
- Poor quality or improper quality of DEF will cause this DTC to set.
- A sticking DEF injector that affects the DEF injection quantity will cause this DTC to set.
- Any unmetered DEF in the SCR catalyst will cause ammonia slip or low NOx conversion efficiency and sets this DTC.
- Accumulated crystalloid DEF in the mixer chamber or SCR catalyst will cause this DTC to set.
- Cover in 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 operation is nearly 130 psi 900 kPa).
- Any induction system problem or exhaust system problem will cause this DTC to set.
- Slow or skewed mass air flow (MAF) sensor may set this DTC. Use the Scan Tool Data List or a known good vehicle to determine nominal values.
- Slow or skewed EGT sensor 3 may set this DTC. Use the Temperature vs. Resistance table to test the EGT sensor 3 a various temperature levels to evaluate the possibility of a skewed sensor.

Circuit / System Testing DTC P1490