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I just installed a brand new EGR on my neighbors Peugeot Partner II 1.6L HDI Turbo Diesel. As soon as I connected it and tried a bidi self test I got a bunch of codes. Cleared the codes, and now have a permanent P0405 EGR Circuit Low EGR Repeat Raw Signal which won't go away, even with the EGR disconnected. This code was not present prior to installing the new EGR. I could not detect any vibration or movement during the self test when placing my finger on the EGR solenoid.

This is a 5 wire EGR which I believe to be a linear EGR.

The EGR I bought is off ebay from England and is physically identical to the one it replaced. However it has a different part number, but from looking at cross references it should be compatible. I am keeping in the back of my head that the solenoid and potentiometer ( EGR position sensor ) might be wired differently.

So that's one posibility. The other things I'm considering are that there is a problem in the wiring since it's obvious that the connector has been cut off and replaced. The other possibility is the EGR is in fact wired differently and I fried something when I hooked it up.

Here's a look at the connector and it does look like it might have been rewired incorrectly:

enter image description here

My assumption is that the EGR should be wired internally like this:

enter image description here

When I used the continuity check setting on my multimeter to check the EGR I saw that Pin 1 had continuity with both pins 4 and 5 showing a resistance of about 200 Ohms, but not setting off the buzzer which I thought was strange. I got OL on all other combinations of pins.

I tested the harness side and with KOEO I have 5v on Pin 1, ground on pins 2,3 and 5 and nothing on pin 4. So I'm assuming Pin 4 should be B+.

With the key off, the only thing I get is a permanent ground on pin 5.

This makes me think pins 2 and 3 are sensor ground and signal. It also tells me the solenoid is probably power side switched and there will only be power on Pin 4 when the ECU is trying to activate the solenoid. This is opposite the above illustration which shows a ground side switched solenoid. The only other illustration of a linear EGR I've found also shows it being ground side switched.

Another possibility is that the permanent ground is the sensor ground, and that pin 4 is supposed to have power and just doesn't for some reason. That would make more sense based on the illustrations I've seen.

Those continuity readings on the EGR just have me really confused and I'm feeling like my brain is about to explode. Too many potential problems, and all just to help a neighbor. Any advice?

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  • One decent question would do : mechanics.stackexchange.com/q/82071/10976 – Solar Mike Mar 7 at 16:17
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    @SolarMike - These are separate questions with separate answers. This is the way SE is supposed to work. – Pᴀᴜʟsᴛᴇʀ2 Mar 7 at 16:37
  • @Pᴀᴜʟsᴛᴇʀ2 all about one peugeot with egr problems... – Solar Mike Mar 7 at 16:43
  • Is your meter able to measure in the 200 k ohm range. If so, can you measure all the different combination of resistances between pins 1,2 and 3 one the valve and post them? – HandyHowie Mar 7 at 17:16
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    @HandyHowie I'll redo that connector and make sure it's wired correctly, also, I'm thinking since every example I've seen is ground side switched there should be one pin with a fixed B+, probably pin 4. Maybe that wire is damaged or I've got a blown fuse someplace... I'll also check if my multimeter has a high ohm setting... – Robert S. Barnes Mar 7 at 19:02
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OK, so the first thing is that the continuity setting on my multimeter doesn't work very well.. I redid the resistance tests using the regular Ohm-meter setting and was able to identify all the pins:

EDIT

I went back and remeasured both the original EGR and the replacement one while both cold and off the engine. My updated measurements make me suspect that in addition to there being a short in the ECU the replacement EGR is defective. I applied B+ across pins 2-3 and while I could feel a slight jerk, the pintle did not visibly move. I verified it was in the closed position.

Original EGR readings ( Verified Closed Position ):

Pins 1-4 Pins 1-5 Pins 4-5 Pins 2-3
168 Ohms 5.888 kOhms 5.975 kOhms 3.75 Ohms

Replacement EGR readings ( Verified Closed Position ):

Pins 1-4 Pins 1-5 Pins 4-5 Pins 2-3
175 Ohms 155 Ohms 112 Ohms 3.7 Ohms

Checking the connector unplugged with Key On Engine Off:

Pin 1 Pin 2 Pin 3 Pin 4 Pin 5
5v Ground Ground Nothing Ground

Checking the connector unplugged with Key Off:

Pin 1 Pin 2 Pin 3 Pin 4 Pin 5
Nothing Nothing Nothing Nothing Ground

So what I gather from all this is that Pins 1, 4, and 5 are the Potentiometer ( EGR Pintle Position Sensor ) with 1 being 5v ref, 5 sensor ground and 4 sensor signal. Then we're left with pins 2 and 3. One of them should be solenoid ground and one should be B+. Pin 2 is red so I'm assuming by convention that it's the B+ pin. Since they're both ground there must be a short. I turned off the key and tested for continuity between the pins 2 and 3 and got about 175 Mega-Ohms; so the wires themselves aren't shorted.

So that seems to leave an internal short in the ECU between pins 2 and 3 as the only possibility. Basically, my neighbor needs a new ECU, in addition to whatever other problems this vehicle may have.

Please let me know if maybe I overlooked something...

EDIT I found this post on a Peugeot Forum which confirms the pin out for the EGR:

Wiring diagram shows five wires from the EGR go straight to the Engine ECU.

  • Pin 1: 5V
  • Pin 2: Motor Negative
  • Pin 3: Motor Positive
  • Pin 4: S? Not sure what this is Signal maybe
  • Pin 5: 0V
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  • Before you buy a new ECU: Sometimes the inputs are protected by "suppressor diodes". Diodes that, when overloaded, get shorted permanently. Perhaps it is enough to replace an eventual defective diode on the input to restore the ECU. – Martin Mar 8 at 11:55
  • @Martin I'm considering just putting back the original EGR which is permanently forced into the closed position. I don't really have the time to take apart his ECU and try to fix it. I don't even know where I'd get a replacement diode. I did call a place which specializes in repairing ECU's and they wouldn't touch it, said go to the Peugeot dealership... – Robert S. Barnes Mar 8 at 12:39
  • Your readings don’t indicate that pin 4 is part of the potentiometer since it’s resistance didn’t change. The resistance should be constant between the two ends of the potentiometer, then the two readings from the potentiometer ends to the wiper should add up to the end to end resistance, no matter what position it is in. – HandyHowie Mar 8 at 13:17
  • @HandyHowie Those are readings on two physically distinct EGR's, the original broken EGR and then the New Replacement EGR. It would make sense that measurements 1-4+4-5 == 1-5 if pin 4 is the signal pin. Except when it's either fully open or fully closed I would think... – Robert S. Barnes Mar 8 at 16:51

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