The truck CEL is on, and the code is P0401, here is the code description Took it from this linkP0401 OBD-II Trouble
Code
Technical Description
Insufficient EGR Flow
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 EGR (DPFE). These things work together to
deliver the correct amount of recirculation based on engine temperature,
load, etc. The P0401 code means that OBD detected an insufficient
amount of EGR.
Symptoms
You may notice drivability problems such as pinging (a.k.a. pre-ignition
knock) when the engine is under load or the vehicle is at higher
speeds. There may also be other symptoms.
Causes
A code P0401 most likely means one or more of the following has
happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and
needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the
EGR valve only to have the OBD code return. The EGR valve is not always
the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring
engine RPM's & DPFE voltage. There should be a noticable difference
in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to
a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve Read more at: http://www.obd-codes.com/p0401 Copyright © OBD-Codes.com 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 EGR
(DPFE). These things work together to deliver the correct amount of
recirculation based on engine temperature, load, etc. The P0401 code
means that OBD detected an insufficient amount of EGR.
Symptoms
You may notice drivability problems such as pinging (a.k.a. pre-ignition
knock) when the engine is under load or the vehicle is at higher
speeds. There may also be other symptoms.
Causes
A code P0401 most likely means one or more of the following has
happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and
needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the
EGR valve only to have the OBD code return. The EGR valve is not always
the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring
engine RPM's & DPFE voltage. There should be a noticable difference
in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to
a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve Read more at: http://www.obd-codes.com/p0401 Copyright © OBD-Codes.com Insufficient EGR FlowOur emissions expert has put together the following information about the P0401 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code. OBD II Fault Code
Fault Code Definition
Symptoms
Common Problems That Trigger the P0401 Code
Watch This Video for an Understanding of the EGR System
The Basics The exhaust gas recirculation (EGR) system recycles a small amount of exhaust gas from the exhaust system (usually no more than 10 percent) and mixes it with the intake manifold air entering into the combustion chambers. The addition of this inert (or non-combustible) exhaust gas limits the peak combustion temperatures to a range that is below 2500° F, where the formation of nitrogen oxide (NOx) is know to occur. In some cases where the engine is pinging and/or knocking badly from a severe lack of EGR flow, misfires can take place which allow raw hydrocarbons (HC) to be released from the tailpipe. P0401 Diagnostic Theory for Shops and Technicians The engine control module determines proper EGR flow in many ways:
The code P0401 is often not a problem with the EGR valve itself. Rather, the EGR system is not allowing enough EGR to flow back into the combustion process to sufficiently cool the peak firing temperatures. Once the code P401 has been retrieved with a scan tool, the freeze frame data should be documented and analyzed in order to determine what engine conditions were present when the code was triggered. It is recommended that the vehicle be driven in such a way as to duplicate the code setting conditions with a data streaming scan tool connected, so the behavior of the EGR actuating components and feedback sensors can be monitored. Pay close attention to the DPFE readings and make sure that they are changing from a .5 to 1 range to a 3 to 4 voltage range when the EGR System is activated. Also, pay close attention to the EGR duty cycle that typically grows percentage-wise as the EGR Sytem is activated. Common Tests to Determine Whether the Problem Is an EGR Control Problem, a Plugged or Restricted System, or a Defective Feedback Device
Note 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 EGR
(DPFE). These things work together to deliver the correct amount of
recirculation based on engine temperature, load, etc. The P0401 code
means that OBD detected an insufficient amount of EGR.
Symptoms
You may notice drivability problems such as pinging (a.k.a. pre-ignition
knock) when the engine is under load or the vehicle is at higher
speeds. There may also be other symptoms.
Causes
A code P0401 most likely means one or more of the following has
happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and
needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the
EGR valve only to have the OBD code return. The EGR valve is not always
the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring
engine RPM's & DPFE voltage. There should be a noticable difference
in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to
a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve Read more at: http://www.obd-codes.com/p0401 Copyright © OBD-Codes.com |