ࡱ > bjbj "* j j l 6 6 6 6 6 6 6 J < < < < H J p p p p p p p p $ A a 0 6 p p p p p 0 t 6 6 p p E t t t p 6 p 6 p t p t t 6 6 p d lTJ < " R [ 0 5 t 5 t J J 6 6 6 6 Repair an EGR with Device Trouble Code P0405 My 1998 Trooper Check Engine Light came on. I read out the DTC and it indicated P0405. This happened about three years ago and I repaired it as described below. The problem came back again a few months ago and I did the same repair. Background: The computer (Powertrain Control Module- PCM) commands the position of the EGR and detects whether the EGR responded correctly. The EGR pintle (the thing that opens and closes in the valve) is connected to the wiper of a potentiometer. The PCM measures the voltage on this wiper to detect if the pintle is positioned correctly. See the figure below. Terminals A and E carry the current to the coil in the EGR that moves the pintle. Terminals B and D are the ends of the pot. Terminal C is the pot wiper. Physically, the connector is the one mounted on top of the EGR. Since the terminals A, B, C, D, E are in a line across the connector, there is no problem guessing which is which. The outer two are the coil, the next inner two are the ends of the pot and the center one is the wiper. The Problem: Both times that I got the DTC P0405, the connection to one of the ends of the pot was broken. The break was deep inside the EGR. The trouble shooting information basically guides you to determine if there is a break in the pot circuit and where it is, inside the EGR (so you buy a new one) or in the cabling. I would start by measuring the resistance between terminals B and D. The manual says it should be between 5 and 5.5 K ohms. I believe that should actually be around 10 K ohms. Of course since the PCM is reading the voltage on the wiper, any resistance value would work. Any value other than infinity (open circuit) that is. Infinity is what mine measured when it failed. Of course you need to check the resistance from the wiper, terminal C and terminal B or D in case the break is to terminal C.. The pot is formed by depositing conductive strips on a ceramic substrate about the size of a postage stamp. The figure below shows the pot. Note how the right most conductive strip has deteriorated. Somewhere along the right-hand strip there is a break. Opening the EGR Opening up the EGR took some doing. In fact, I made some mistakes the first time which could confuse this description but I will try to explain as I go along. To open the EGR I cut a vertical slit in it as shown below. I used my Dremel Tool but a hacksaw should work also. To close it up later, I just put a hose clamp around it. After you finish the cut, separate the can a little and slide the lower part including the flange down out of the can. The coil will come out with it. When the coil comes out, terminals A and E slide out of the upper part and stay with the coil. Be careful. Below is a picture of the two halves with terminals A and E labeled. They are just prongs that you are viewing almost straight on. The part on the right above comes apart as shown below. I have labeled a few things. Glob is a glob of silicone sealant from the last time I repaired the EGR. A and E are where terminals A and E were fitted through two slots. X is a part that I had to add. The first time I took this apart I didnt know how it was made so I cut out a rectangle in the plastic around terminals B, C, and D. I should not have done that so I had to fabricate a spacer to replace what I had cut out. That is part X. Instead of cutting out the rectangle, I should have just pealed back a lip on the Ring. The actual lip is just under the front leg of the letter R. It goes all around, through the missing rectangle and back to R. It isnt really needed because when you reassemble the unit, the metal plate (with GLOB on it) will keep everything together. Once you peal back the lip and pull it apart you can see the ceramic substrate for the pot, terminals B, C, and D, and on the other piece, the wiper made up of those two silver/white prongs. Now you can gently pull out the substrate like below. This view is the backside showing terminals B, C, and D. The Repair: On the front side, I cleaned it off a little of the gook and most of the right strip flaked off. I repaired the strip using a special Circuit Writer pen that deposits a silver trace. The figure below shows that pen and the cleaned ceramic. I got the circuit writer from RadioShack but I dont think they carry them anymore. I have seen them on Amazon and other places. They cost about $10-$15. The figure below shows the repair. Frankly I was doubtful this would work the first time because I am replacing a restive material with a silver trace that has basically zero resistance. I gather the PCM is somewhat forgiving about what it will accept for a reading. I guess as long as the voltage changes when the pintle moves, that is good enough. Use an ohmmeter to verify that you made the connection. Then, assembly is the reverse of the process. (Dont you just love it when the manuals say that?) As I said, I put a hose clamp around the whole unit to keep it from opening where the can was cut. I hope this is of use to someone. It got me three years more out of the EGR and another three I hope. - . ( I V W { | & j U j U j< U j U j] U jI U j U 5CJ \ j; U j CJ U 5CJ \ CJ - . ( ) H I V W @ A A z { } ~ ' ( ! ! " 1h/ =!"#$% ; D d ),, T C 0 A E G R - 4 0 5 . j p g R "c o D Fg "c JFIF C $.' ",#(7),01444'9=82<.342 C 2!!22222222222222222222222222222222222222222222222222 " ] !1AQa"2q#3BR$br4CDSTcs%&6t'5deEu ? [}[6@ kH1?X,r1==VtPV'LE Ըٓd f* ?Lb01f a1b́?}I*mD Wg4][J@Q J(o)}Iդ9eТw ceoRQBbъqjYp>t^K"!S);zU_J=>J3@ӆ?lP0 v+/26ppk.O,¾;bltɲ?+[(w#hs4䃦&ze͍Dj,zLth1 &7;ñwe,۸O)O*|"kkV 4 OsQ& xLl&]Z