04.5-05 Chevy Duramax Diesel
EGR Code "Finger Stick" & EGR Block Off Plate- LLY Motor
This EGR Override Circuit "Finger Stick" is For the GM 2500/3500 LLY 6.6L Duramax Diesel Engines (Years: 2004.5, 2005).This circuit modifies the MAF signal to the computer on the LLY engines (Not LB7, Not LBZ, Not LMM) to expected levels when the EGR is blocked off, modified or a big free flowing exhaust system (removing the cat) causes the ECM to set an EGR code and display the check engine light / service engine soon.
This "Finger Stick" will prevent a Service Engine Soon (check engine engine) light from illuminating and will prevent the ECM from displaying DTC codes related to an EGR modification or larger exhaust.
This modification is required on most California and Northeastern emission trucks and some federal emission trucks to stop engine limp and turn off the check engine light due to the lowered back pressure of removing the front pipe.
Package comes complete with COLOR DETAILED wiring instructions!
This circuit once installed in not detectable by GM scan tools
Average install time 30min.
LLY ENGINE ONLY!! -
There are two common methods of defeating this system. The first is to simply unplug the EGR electrical connector. The second is to install a plate to physically obstruct the flow of EGR gasses. Both of these alterations will typically result in the P0401, P0404, plus P1404 (Exhaust Gas Recirculation Closed Position Performance) and P0405 (EGR Position Sensor Circuit Low voltage) will typically set with the EGR connector unplugged.
The key operational difference among these groups is how emission related DTCs are processed. In short, the FE9 trucks treat EGR system DTCs as non emissions and simply stores a record of the fault with no corrective action. The NE1, YF5, and VCL trucks typically require 2 trips of the code and then trigger an SES light and some form of reduced performance. The setting of codes and SES lights can be corrected and will be covered in a later paragraph.
Why do the Codes set?
When the ECM activates the EGR valve it is looking for a certain response on the various channels associated with the system. Unplugging the valves electrical connector also eliminates the electrical voltage feedback from the valve. When the EGR system operates, the ECM is essentially looking for a change in the MAF (mass air flow) signal to verify that a part of the engines combustion air is coming from another source than the air box. As an example, an idling Duramax will flow approximately 37 g/sec of mass air with the EGR off. When the EGR activates (say 10% duty cycle) the resultant change in flow will show approximately 27 g/sec of mass air. This is because the engine is now receiving part of its air flow from the recirculation of exhaust.
Dealing with the Codes:
The LLY FE9 trucks can simply ignore them as there is generally no SES light or corrective action taken, only DTCs store in the computer. The LBZ will set the same DTCs, and will also typically set the annoying SES light. There are several ways to deal with the codes associated with the EGR system. The code blocker "Finger Stick" is the simplest device that can be used to emulate the altered MAF signal during periods where the ECM is calling for EGR operation.
It is important to note that not all vehicles react or respond the same to alterations, modifications, or conditions. This is true for both emissions and performance modifications. Some trucks even been known to set DTCs (Diagnostic Trouble Codes) and trip the SES (Service Engine Soon) light in factory stock condition. I should also note that tampering with emission control devices is against the law regardless of whether your State or Municipality performs periodic emissions checks or not. That being said, I feel that there are far more negatives rather than positives to having these systems active on a diesel engine. Catalytic converters can cause excessive heat loading in the engine, turbo and exhaust system. EGR systems can load or potentially even plug the intake tract with soot. Even when operating under normal conditions EGR systems redirect abrasive soot and carbon back into the combustion chamber and crankcase. Closed crankcase ventilation systems draw oil vapors in from the crankcase via the turbo and intercooler system. These oil vapors coat the intake tract decreasing efficiency. Combine the oil and exhaust soot and you get a gooey tar like substance that can build up and severely restrict airflow. Both EGR and PVC systems replace a percentage of clean, oxygen laden air with a lesser quality air, oil vapor and exhaust gas mix that has less performance potential.
The Duramax engine has evolved:
- LB7 - 01-04
- LLY - 04.5-05
- LBZ - 06-07 (classic)
LMM (new body GMT 900)
The LB7 was used from 2001 model year until mid 2004 model year.
In mid 2004 the LLY series was released. In 2006 the Duramax changed again.
The early 2006 engines were still called LLY and the later 2006 and 2007 "Classic" became the LBZ. This creates some confusion as the 06 LLY is distinctively different from the 04.5-05 LLY. The 2006 LLY and LBZ engines are essentially the same when it comes to modifications.
The LMM began in the new body style GMT 900 series trucks in 2007.
The simplest way to verify which series you have is the VIN# of the truck. The 8th digit is the engine ID and it will either be a 1, 2, D, or 6.
Example: 1GCHK29143Exxxxxx for LB7 and 1GCHK29245Exxxxx for LLY.
It is important to know this as while the engines are essentially the same at the core, the electronics, turbochargers, electronics, and injectors are different among the variants. The 10th place in the VIN number identifies the model year on these vehicles. The example above shows the 2003 model year LB7 and 2005 LLY
Any installation you make is done at your own risk. Any manufacturer can not and
will not be responsible for any damages, real or perceived, to you, your truck,
or your marital life in whole or in part. Same goes for these installation
directions. I did this as a favor to the forum members to save them some reading
time on an interesting subject. Read all these directions before
installing. Ask questions first, install second.