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Discussion Starter · #1 ·
I have a 1999 K1500 with the 5.7L and have had this light coming and going. I know what the repair manual say but has anyone else out there found a quick fix for the stupid thing. After it goes on then the codes for the bank 2 o2 sennsor kick on then egr valve stuck closed finally followed by cat below specs. Truck runs fine, has not affected fuel economy or driveability. Please Help have inspection by the end of Jan. The code is P0405

Premium Member
1,786 Posts
Disconnect battery for 60 seconds.

That should clear all codes.

Then if it comes back on you check it right away.

It’s possible it is the O2 sensor, but just clear the codes first, and see if it comes back.

O2 sensors are cheap and easy to replace.

2,470 Posts
Re: RE: CHeck Engine Light on for EGR Circ Low

ljjcsautomotive said:
replaced o2 sensor and still the same trouble codes. Guess I'll have to trace the wires and find the problem
The code P0405 indicates that the voltage level is low on circuit A. That suggests to me that the sensor is defective.

Here is a pretty good site for codes and their causes: Diesel Stop

I haven't found much info on P0405 Exhaust Gas Recirculation Sensor 'A' Circuit Low but the related code P0401 may shed some light on your problem and give you a couple of places to look: (from: )

P0401 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 (DPF). 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.

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.

A code P0401 most likely means one or more of the following has happened:

* The DPF (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

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. There should be a noticable difference in RPM's with the EGR open
* Clean out the EGR valve to remove deposits
* Replace the DPF sensor
* Replace the EGR valve

Please keep us updated on what you find out.
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