This applies to the 3.1 "3100" SFI V6 engine. Not sure what other engines it applies to.
The following directions are to resolve the issue of a trouble code for your EGR, which are the following:
OBD1-1.5(1995 and before) Codes:
75 digital egr #1 solenoid error
76 digital egr #2 solenoid error
77 digital egr #3 solenoid error
OBD2 (1996 and up) Code:
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
Step 1: Retrieve your diagnostic trouble codes. For OBD1 vehicles (93 & before) you can retrieve these codes by using a jumper wire (or paperclip) between the A and B terminals on your ALDL connector. Turn your ignition key to the "run" position but do not start the car. Your "Check Engine" or "Service Engine Soon" light will begin flashing. The first set of flashes you will see will be one long flash then 2 short flashes in rapid succession. This indicates code number 12, or that the diagnostic system is functioning properly. From here on any additional flashes will indicate a trouble code that your diagnostic system has detected, until you see code number 12 again. Each code will begin with a series of 1 or more long flashes, indicating the first digit (or the "tens" place) of the trouble code. Following the long flashes, a series of 1 or more short flashes indicates the second digit (or the "ones" place) of the trouble code. Each code is separated by a short pause.
If you feel uncomfortable doing this, many reputable auto parts chains will be able to pull your codes for free (Pep Boys, Auto Zone), or most garages and repair shops will do so for a fee. You can also purchase an ALDL cable, which, used in combination with your laptop, will give you the information you need. Finally, you can purchase an OBD1 scantool from a number of online sources. If you choose to purchase a scan tool, make sure that
List of OBD1 and OBD1.5 codes: http://www.extreme-check-engine-ligh...%20Decoder.htm
For OBD 1.5 (94-95) and OBD2 (96+) Vehicles, the options for retrieving your diagnostic trouble codes are slightly more limited. The cheapest way to retrieve your codes in this instance is to go to one of the local reputable auto parts stores (Pep Boys, AutoZone, etc) and they will scan your codes, free of charge. Note: OBD 1.5 vehicles are GM only, and therefore finding a location to scan your codes for you is more difficult. My local Pep Boys was able to pull my codes for free, however this varies by location. Consult the service department there about the cost and ability of pulling trouble codes at that location. Another option is to purchase a scanner, available from a number of online sources. OBD2 scanners are plentiful and easy to find, however scanners with an OBD1.5 attachment can be quite difficult to locate. Finally you can purchase (or make your own, contact site member RobertISaar for more information) ALDL cable.
List of OBD2 trouble codes: http://www.obd-codes.com/trouble_codes/
Step 2: Removing the EGR Valve. Using a deep well socket and wrench, remove the 2 bolts that connect the EGR to the engine. Disconnecting the electrical connectors from the throttle body (Idler Air Control and Throttle Position Sensor) may make it easier to locate the bolts. The two bolts are located directly opposite from each other. The one in the front is easy to see, however the one in the back can be difficult to locate, however, both bolts are the same size. After removing these two bolts, lift up on the EGR to separate it from the engine. There may be a large amount of carbon buildup, making it difficult to separate. A gentle tap with a rubber mallet will break loose this carbon, allowing the removal of the EGR valve. Using a small flat head screwdriver, you can carefully separate the electrical connector from the EGR valve.
When moving the EGR Valve, be careful not to damage your EGR gasket. Set the valve aside for reassembly later. Examine the EGR ports as well as where the EGR rests on the engine. Make note of any carbon buildup (you may notice a milky tan substance as I did in mine as well). You will be cleaning this up later.
Step 3: Removing the throttle body. First, using a deep well socket and an extension, remove the two bolts holding the air filter box on. After removing these, disconnect any wires and vacuum hoses from the air inlet tube. Removing the inlet tube is simple, using a flat head screwdriver loosen the hose clamp holding it on. A gentle tug and it should come off. You will now have a clear view of the throttle body butterfly. Examine carbon buildup on the butterfly. This buildup may lead to other problems with your engine, including hesitation and stalling. You will be cleaning this later. Using a deep well socket and an extension, disconnect the bolts holding the throttle body on. Remove the lower throttle body bolt first, as removing the upper one first will make removing the lower one more difficult. A coolant pipe runs directly in front of the lower throttle body bolt, making it difficult to remove. Some time and patience and the bolt will eventually come off. Next remove the upper throttle body bolt, which is completely open and easy to see. Before doing so, I would recommend removing the bracket that holds the throttle cable on. Be careful not to twist the throttle cables too badly, or mess up their routing. Set the throttle body and the cable assembly aside for cleaning later. You may notice upon removin the throttle body You will now have a clear view into the intake plenum.
Step 4: Cleaning!
You will need:Begin cleaning the EGR valve itself. Using the carburetor cleaner, spray the inside of it as well as the EGR opening on the engine. Let the cleaner soak in briefly and then blow it out using the compressed air. Be careful as this part can get very messy. You may have to do this a few times to clear out all of the gunk. Use more compressed air to dry out the cleaner. Inspect the EGR gasket. If it is in good shape, reuse it. If it is NOT in good shape, get a new one, they are only a few dollars.
- Red shop rags or lots of paper towels
- Carburetor Cleaner (Throttle Body cleaner is not needed)
- Compressed air
- A new throttle body gasket (available at your local auto parts store for less than $5)
- A wire coat hanger
- A cordless power drill
- A piece of speedometer cable or brake cable about 10 inches long.
Now comes the fun part.
Look in through the throttle body opening in the intake plenum, notice the carbon buildup. Using more Carburetor cleaner, thoroughly soak the carbon, especially around the area of the EGR passage. Let it sit. Using a pick tool of some sort (a flat head screwdriver, for instance) scrape out as much of the carbon as you can around the EGR passage. Then using a shop rag, wipe out as much of the carbon as you can. Depending on how much carbon is build up, you may have to do this several times.
Examine the opening of the EGR passage that connects the intake plenum with the EGR Valve. Chances are, the reason you are receiving a trouble code for the EGR is due to a clog in this passage.
Using the flexible snorkel (the little red plastic hose) on the can of carburetor cleaner, spray as much of this passage as you can. You can spray this passage both from the side of the intake plenum as well as from the side of the EGR. Using the piece of wire coat hanger, gently push it into the EGR passage until it doesn't go anymore. Twist the piece of wire coat hanger and attempt to dig out as much of the carbon as you can. Little pieces will break off and fall into the intake plenum. Use the shop rag wipe out as much of it as you can. You may have to do this a few times as well.
Eventually you will get to the point that you are no longer making any progress. At this point, install the piece of speedometer or brake cable into your drill. Put the drill in reverse and use it to clear out the hole, similarly to the way a plumber uses a pipe cleaning snake. I found it was easier to clean it out by pushing it in from the plenum side towards the EGR. Keep pushing the cable in and out until it pushes all the way through and you see it come out the EGR opening. Run it back and forth a few times just to make sure any blockage has been cleared. Doing this will take some time and more carb cleaner. After you have successfully cleared the passage, wipe up any residue you can with more carb cleaner and shop rags.
Now let's focus on the throttle body. Using carburetor cleaner and a shop rag, clean out the the butterfly valve on the throttle. You can open and close this butterfly by using the throttle cable attachment. Be careful when doing this that you do not bend the butterfly valve, as it will cause you more headaches.