Duramax Reductant Pressure Sensor Location and Function

The duramax reductant pressure sensor is a component of the selective catalytic reduction (SCR) system, which reduces the nitrogen oxides (NOx) emissions from diesel engines. The SCR system injects a reductant compound or a diesel exhaust fluid (DEF) into the exhaust in front of the diesel particulate filter, NOx trap, and/or the catalytic converter via the reductant injection valve (solenoid). The reductant reacts with the NOx and converts it into harmless nitrogen and water vapor.

The reductant pressure sensor provides the reductant control module with a voltage signal proportional to the reductant pressure generated by the reductant pump. The reductant control module varies the duty-cycle of the pump voltage to maintain reductant pressure within a calibrated range.

Location

The duramax reductant pressure sensor is located near the reductant tank and pump assembly, which is typically mounted on the frame rail under the driver’s side of the vehicle. The sensor is connected to the reductant pump and sensor assembly harness, which has a four-pin connector. The sensor resembles a small black box with wires attached.

The following table shows the pinout of the reductant pressure sensor connector:

Table

Pin Wire Color Circuit Function
1 Yellow 2500 5 V Reference
2 Black 450 Low Reference
3 Brown 2501 Reductant Pressure Signal
4 Gray 2502 Reductant Temperature Signal

Function

The reductant pressure sensor measures the pressure of the reductant in the reductant pump and sensor assembly. The sensor responds to pressure changes in the reductant system. The reductant control module supplies 5 V to the sensor and provides a ground on the low reference circuit. The sensor returns a voltage signal on the reductant pressure signal circuit that varies with the reductant pressure. The reductant control module monitors the sensor signal and compares it to a desired pressure value. If the sensor signal is out of range or does not match the expected value, the reductant control module will set a diagnostic trouble code (DTC) and illuminate the service engine soon (SES) light.

The reductant pressure sensor also measures the temperature of the reductant in the reductant pump and sensor assembly. The sensor returns a voltage signal on the reductant temperature signal circuit that varies with the reductant temperature. The reductant control module monitors the sensor signal and uses it to adjust the reductant injection rate and the reductant tank heater operation. If the sensor signal is out of range or does not match the expected value, the reductant control module will set a DTC and illuminate the SES light.

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