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Lost Communication with Radio , did you replace factory radio ?
The communication among control modules is performed through the High speed GMLAN serial data circuits and the Low speed GMLAN serial data circuit. The modules that need real time communication are attached to the High Speed GMLAN network. The body control module (BCM) is the gateway between the high and low speed networks. Refer to Body Control System Description and Operation for more information about the gateway.
Signal supervision is the process of determining whether an expected signal is being received or not. Some messages are sent on a periodic basis and are interpreted as a heartbeat of a device. If such a signal is lost, the signal supervision part of the software will set a no communication DTC (U code) against the missing device. This code is mapped on the scan tool screen as a code against the physical device. A lost communication DTC typically is set in modules other than the module with a communication failure.
Does the vehicle start an run ?
What does that mean? EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor (DPF). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0402 code means that OBD detected an excessive amount of EGR.
Symptoms You may notice drivability problems such as the engine may surge off idle. There may also be other symptoms.
Causes A code P0402 most likely means one or more of the following has happened: * The DPFE (differential pressure) sensor is faulty and needs to be replaced * There is a blockage in the EGR (most likely carbon buildup) * The EGR valve is faulty * The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions With a P0402, it is common for people to replace the EGR valve, only to have the problem return. The most likely solution is to replace the DPFE sensor. * Check the voltage at the DPFE sensor both at idle and when the EGR is open * Replace the DPFE sensor