wolfdogg

would have rather posted this topic across a broader audience, ie.. a maintenance and repair topic, but here it goes.

i have a 2007 chevy equinox 3.4l

i have a p0405 DTC that is persistent. i have isolated the problem to what i assume to be the 12v supply wire seems to have a bad connection.

when i meter the supply line it, i reads 11.74 volts, and when i put it under load, ie.. a test light, it drops to 0 volts. i managed to test that i am getting the same scenario on the red wire on the engine control module, which from what i tested is the correct wire that leads to the egr feed. i metered it there on the engine control module, and registered the near 12v, but when i put a test light on it, it cant supply the load, and drops to near 0v.

is this normal behavior for this wire? the reason i used the test light is because i read it in here P0405 Exhaust Gas Recirculation Sensor A Circuit Low , and the reason i mention this is i can see an instance where the amperage capacity of the load from the main cpu might not be delivering that which will power up the test light, but i DOUBT this. so i assume the connection is faulty somewhere previous to this.

what i dont have is the schematic, but i need it. i cant seem to find it online, and the correct images at the autozone.com repair manual arent loading for me currently. what i want to see is where that supply line traces to.

what i havent figured yet is wether the red line i tested on the engine control module is the feed out, or feed in to the module itself. all i can say is if im facing the engine from the front, the module sits on the right side above the battery, and the connector i found the wire in was the left hand connector, as opposed to the right hand connector. maybe somebody knows if this is the feed or not. i can say that the guage of wire was the same so i assume its the output of the module, and the direct feed to the egr 12v hot.

So, where im at now, is im assuming the problem lies either in, or before the engine control module, since i have not yet determined wether i metered the input or output on the module. assuming its the input, then i would assume the supply somewhere presious to this module has a bad connection. i need someone to tell me where all the connectors are that lead up to this from the cpu.

also, i havent found the cpu yet, i guess its near the glovebox. once i find the schematics, and the cpu, i want to meter and test with the test light the output that runs this circuit.

any experience here that might have a tip as a known bad connector, or a symptom of a bad computer module?

EinST

Welcome to the forum. P0405 means the EGR pintle position signal level dropped below 0.2V. You EGR valve should have the following electrical connector:

Terminal A, GRY wire, EGR Sol Low from ECM
Terminal B, TAN wire, EGR Pos Low Ref from ECM
Terminal C, BRN wire, EGR Pos Sig to ECM
Terminal D, GRY wire, EGR Pos 5V Ref from ECM
Terminal E, ORG wire, EGR Sol High from ECM

Terminals B, C, and D are for the EGR pintle position sensor which is basically a potentiometer that takes in ground and 5V reference and returns a voltage signal between 0.5V and 4.5V give or take that corresponds to the pintle position. See if you can back-probe terminals C and B and measure the voltage level across with key on. Then, remove the electrical connector and then measure the reference voltage across electrodes D and B on the connector, again with key on. Also, check the continuity, i.e., resistance, between electrode B and a known chassis ground.

wolfdogg

thank you much for your response.
i did the tests, i found that
terminals b & c connected wtih key on is .771 volts,
terminals d & b disconnected gives a clean 5.0 v
and a & b have a clean 0.0 ohms to the chassis of the egr clamp which i have found to be a good ground.

i did some more testing on the POT and have 5.58 Kohms on terms D & B,
6.0 KOhms across D & C
and 1.7Kohms to 2.1Kohms across terminals C & B. im not sure offhand what terms the load goes across, isnt it Termincal C and which ever is the reference, either B or D, see my note below on this.

Is it sounding like its a bad pintile POT since the voltage across it is only .771v if im reading into this right, or is this normal?


note, when i check terminal E to ground, im no longer getting the near 12 v that i was before for some reason, im getting below 1 v, in reference to chassis ground, and in reference to Term A as well.



on another note---
when you said that Terminal B is 5 v ref, Reference is usually ground in automotive correct? I think terminal A & B are the refs, and terminals D and E are the Low and High arent they?
meaning;
Terminal A, is a Ref, and
Terminal D is a 5v Low, not a ref?
if not, then please disregard this last paragraph. but i thought that i was getting 11.7 v across the ORG (E) to ground, and 5v across the GRY (D) to ground.

EinST

Well, reference voltage is just that, a ground reference or some positive or negative voltage relative to the ground. So, terminal C returns some voltage proportional to the pintle opening and the 5V reference relative to the low (ground) reference. I don't think 0.771V is bad with a small pintle opening.

The ECM controls the pintle position by a pulse width modulated signal. It looks on a scope as a square wave with variable width, with larger the widths, the greater the pintle movement. Thus, I'm not sure how your meter is interpreting the voltage signal.

It could be that there's a dead spot in the sweep range or some other problem. The former can be tested by removing the EGR valve and then pushing on the pintle while monitoring the voltage on terminal C. It should smoothly rise to 4.5V without any dropouts. On the latter, I don't know but you may want to post the freeze frame data.

wolfdogg

thanks for that, yeah figured as much on the ref, thanks for clarifying.
didnt realize its PWM-pulse width modulation signal, cool. sounds kind of extravagant, but guess theres a good reason for it. i have seen it on an oscilliscope, but its been more than 10 years. thanks for jogging my memory.

i will try to manually test it, i think i will use an analog VOM for that.

so im starting to wonder if the computer is bad now.

since you have experience in this field, wouldnt you say the HI voltage feed should be able to handle a 12v test lamp? because the test lamp creates a voltage drop which drops the source to near 0 volts, and wont light. it tells me that a connection just needs re-seating on the feed side somwhere, or the computers are feeding a poor voltage.

if you suspect this is the case, i would like to simply find the output at the cpu and see if its giving me the same response on the test light. surely the current would be enough amerage to run a test light if its expected to trigger the valve solenoid wouldnt it?

EinST

I wouldn't worry too much about the solenoid actuation signal from the ECM. Unless you have a scan tool that can tell the ECM to open the EGR valve certain %, there's no way for you to be sure what to expect on terminal E. Besides, I think you'll get DTC P0403 if there's something funny going on with the circuit across terminals A and E.

As I posted originally, "P0405 means the EGR pintle position signal level dropped below 0.2V." Look for a dropout on terminal C or an intermittent open or short to ground on the BRN wire (or GRY wire, even).

wolfdogg

i think you are spot on.

i think it was both terminals B and C, as well as D and C, i found with a DMM, across the sweep a proportional amount of resistance, but when i hit the spot to where its pressed almost all the way in, i was noticing a drop to OL, and i felt its a bit loose in that area as well. then i pressed it in further and the resistance came back. it appears as if thats the exact location it sits when we drive it mostly, where vibrations have roudned it out, and messed it up.

Isnt the 'pintile pressed most of the way in' position 'valve open' position? and isnt the valve mostly open when driving? if so, it makes sense that the sensor just got rounded out inside and tired, especially since prior to this house, we lived off a dirt road, and the suv is no stranger to road vibration.

i wish i could locate my VOM over here to do an analog ohm meter test, which is what analog meters are primarily used for still, ohms/voltage sweeps across a range, and or intermittent conditions and fast response.

does it sound to you that we have come to a conclusion>? if so, then i will make a decision over here soon to replcace it. im hoping on the internet i can find the sensor part instead of having to replace the whole thing...

on the sensor it says 12581878 GM 1846A, i am hoping that leads me to a part replacement.

EinST

It does sound like you found a bad EGR valve and kudos to you for troubleshooting first before throwing parts at the problem. I'm not sure if they actually sell pieces of the EGR valve, though.

wolfdogg

thanks for your technical support. was a comforting feeling having some help :-)

the cheapest i see this part is here Air Check Valve - SAE Parts Store- Warehouse, Ford,GM,Chrysler,Dodge advertised for buick rendevous cx saturn relay. its going for $54.95. sure doesnt look like the kind of site i would order from though. i found it here 2000 - 2007 General Motors Saturn EGR Valve
for $61.11
and here
07 2007 Chevrolet Equinox EGR Valve - Air Intake - AC Delco - PartsGeek
for $63.98?

any suggestion on a reputable website from the choice of the 3 there?

EinST

I haven't personally used any of those sites. I usually order parts like that (ACDelco if possible) from RockAuto. There's even a 5% discount code (goes in the "How did you hear about us" box) at New Rock Auto Code - Bob Is The Oil Guy. You'll probably want to get a new gasket as well. One thing with RockAuto is that you have to watch the shipping charges when multiple warehouses are involved.