P128B Code: Meaning, Causes, and Symptoms | OBD2 Codes

P128B – Fuel Rail Pressure Sensor 2 Internal Performance

 

P128B Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

P128B Possible Causes

 

Faulty Fuel Rail Pressure Sensor 2,Fuel Rail Pressure Sensor 2 harness is open or shorted,Fuel Rail Pressure Sensor 2 circuit poor electrical connection

 

P128B Description

 

The fuel rail pressure sensor transmits fuel pressure and temperature information by serial data. The fuel rail pressure sensor internal microprocessor allows 4 separate sensor outputs from one 3 wire sensor. The Engine Control Module (ECM) supplies the fuel rail pressure sensor with a 5 V reference circuit, a low reference circuit, and an asynchronous signal/serial data circuit. The asynchronous signal means communication is only going from the fuel rail pressure sensor to the ECM. The ECM decodes the serial data signal into separate voltages which are displayed on a scan tool as the voltage inputs from the Fuel Temperature Sensor, Fuel Rail Pressure Sensor and Fuel Rail Pressure Sensor 2.