Took my pickup into the stealer to get some warrenty work done. I was having the surging problems at low rpms. Dealer just called, they said my EGR Valve was bad. Does that sound right? Also, will they reflash with the lateset updates when replacing, becasue when I asked the guy if the mechanic had done the reflash, he didn't know.

Thanks

EGR valves have been somewhat common on LLY engines. For the most part we dont update unless we have a customer concern or a recall.

The reasons for this very, sometimes updates may not be needed from one truck to the next. Sometimes you may change something that the customer had no issue with.

Once you update you cant change it back.

I took mine in last week and had the low speed surge reflash done. I have had the EGR unplugged for 5 or 6 months and they didn't notice it. (I checked when I got the truck back. The male plug is up against the female to look like it's connected, but it's not plugged in) The invoice stated there were NO codes. I thought uplugging the EGR would set an internal code even though the SES light will not come on. Shouldn't it throw a code?

I took mine in last week and had the low speed surge reflash done. I have had the EGR unplugged for 5 or 6 months and they didn't notice it. (I checked when I got the truck back. The male plug is up against the female to look like it's connected, but it's not plugged in) The invoice stated there were NO codes. I thought uplugging the EGR would set an internal code even though the SES light will not come on. Shouldn't it throw a code?

I haven't gotten one on mine... I've checking with OBDII scanner/recorder.

but, I'm getting low rpm surging with the latest reflash...

By unplugging the EGR valve, is it stuck open or closed then?

I'm sure hoping it's closed..

I thought you had to unplug it when the truck was cold then it would assure that it was closed

Put a blocker plate in and it won't matter whether it stays open or closed, nothing will get through!

Document ID# 1369855
2005 GMC Truck GMC K Sierra - 4WD
Exhaust Gas Recirculation (EGR) System Description

The Exhaust Gas Recirculation (EGR) System is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by high combustion temperatures. At temperatures above 1 371°C (2,500°F), oxygen and nitrogen combine to form oxides of nitrogen (NOx). Introducing small amounts of exhaust gas back into the combustion chamber displaces the amount of oxygen entering the engine. With less oxygen in the air/fuel mixture, the combustion pressures are reduced, and as a result, combustion temperatures are decreased, restricting the formation of NOx.
The EGR valve motor is a direct current (DC) stepper motor utilizing a worm gear that extends from the motor to push on the EGR valve stem. The worm gear is not attached to the valve stem, and can only force the valve open. A return spring is used to force the valve closed.
The mass air flow (MAF) sensor signal is used by the engine control module (ECM) to detect the proper amount of EGR flow. One EGR flow test is performed per ignition cycle. The ECM will close the EGR valve for 5 seconds, then open the EGR valve to 100 percent for 5 seconds. The ECM will then calculate the MAF difference and determine if the proper EGR flow has been detected.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1369855&psdid=1058&evc=sm#ss1-1369855">Exhaust Gas Recirculation (EGR) System Operation


http://service.gm.com/engif/000/001/382/1382620.gif
http://service.gm.com/tif.gif (http://service.gm.com/servlets/RetrieveTif?pic=1382620)
(1)EGR Valve Position Sensor(2)EGR Valve Worm Gear(3)EGR Valve Return Spring(4)EGR Valve Head(5)EGR Valve Stem(6)EGR Valve Motor
The exhaust gas recirculation (EGR) valve is controlled by the engine control module (ECM) through the EGR motor high control and EGR motor low control circuits. The ECM supplies voltage that is near ignition voltage to the high and low control circuits at all times. This voltage is used by the ECM as a reference voltage during non EGR operation in order to detect circuit failures. The ECM will pulse width modulate (PWM) the low control circuit to ground and an increase in amperage on the high control circuit can be observed with a DMM when the EGR valve is commanded open. A lower pulse width will increase the open position of the valve. In order to close the EGR valve, the ECM will PWM the high control circuit to ground.
When the ignition is turned ON, the ECM will drive the EGR motor worm gear out with just enough force to touch the EGR valve stem. The ECM will do this 3 times in quick succession. This action determines the minimum closed position of the valve and only happens once per ignition cycle. If the valve is prevented from closing all of the way after the minimum closed position is learned, the scan tool EGR Position parameter will not reflect this position until the next ignition cycle. The EGR motor worm gear is not connected to the EGR valve stem and can only push the valve open. The valve is returned to the closed position by a return spring.
The ECM uses the EGR position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1369855&psdid=1058&evc=sm#ss2-1369855">EGR Valve Control Enabling Conditions.

Exhaust gas recirculation (EGR) valve control will only be enabled during idle and cruising conditions while the following conditions are met:
• The intake air temperature (IAT) is more than 5.25°C (41.5°F). EGR valve control will remain enabled until the IAT is less than 0°C (32°F) and will not enable again until the IAT is more than 5.25°C (41.5°F).
• The engine coolant temperature (ECT) is between 60-96.75°C (140-206.15°F). EGR valve control will remain enabled until the ECT is less than 57°C (134.6°F) or more than 99.75°C (211.55°F) and will not enable again until the ECT is between 60-96.75°C (140-206.15°F).
• The barometric pressure (BARO) is more than 74 kPa. EGR valve control will remain enabled until the BARO is less than 72 kPa and will not enable again until 74 kPa.
Document ID# 1369855

:o: Sorry, its a litte on the large side.

So what do you gain by blocking off the egr vlave.

you prevent a lot of exhaust soot from being blown back into the intake. The soot will build up in the intake and reduce performance / economy

Sorry for being thick headed. Does that mean that if the EGR is inpluged that it will stay closed and not let anything through? If it is unpluged will it effect the running of the engine or will it act like a bloker plate. If you don't install a fingerstick will the engine detect its unpluged and not perform properly?
There have been so many posts about the blocker plate and fingerstick, and also unpluging the egr my heads swimming. Not sure what to do. Have been thinking about adding blocker plate and finger. But don't know if we will run into problems if they start smog checking our truck.
Thanks sorry if these are stupid questions. My truck is 06 lbz just started egr codes at about 7600 mi. Taking to dealer to fix.
Thanks Ron.

All I know is that I didn't notice any difference when I unplugged my EGR. I read on here that the ECM will reset defaults if it sees the EGR is not opening. As far as smog checks, with it simply unplugged, if they catch it, all you have to do is act ignorant like you knew nothing about it and plug it back in. Who knows how it came unplugged...... ;)

The EGR if left stock with powertuners (Quadzilla in my case) will possibly make boost sensors go bad, I had one replaced before I put the blocker plate in. A lot of extra soot for the EGR to deal with.

I would highly recommend doing the blocker plate and fingerstick instead of unplugging the EGR. The valve would still creep open under boost.

To the guys running EFI Live, you are still running the blocker plates correct? just no fingerstick when you turn off the EGR?

So can the valve blow open under boost??

Not completely open, but it will creep open slightly. Well, I guess if there is enough boost it could fully open.