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Passed Emissions, Failed EGR Function Check (California)


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Just had my 94 Pathfinder smogged last Friday and it passed everything except for the "EGR Functional Check". They offered to let me leave it there so they could diagnose but I decided otherwise as I know I thing or two about car repair and I also have the Nissan technicial manual for this vehicle.


I followed the trouble diagnoses steps layed for the VG30E beginning on page "EF & EC-28"

  • Checked for ECM codes on mode III and mode IV and received only received "55" (No Errors Detected)
  • Performed EGR Function EF & EC-94 (No issues noted)
  • Checked EGR Temp Sensor Resistance and hardness connector EF & EC-135 (No issues noted)
  • Checked the EGRC-Solenoid Valve EF & EC-135 (No Issues noted)
  • Checked the ERGC-BPT Valve EF & EC-135(No Issues noted)

As per the above bullets, I could not find anything wrong, I don't know where else to go (unless the shop is lying to me). If anyone can offer some additional input I'd appreciate it!


Below is the recent failed emission report, and another from 2014 (both were performed at the same shop), its surprising to me how close the numbers are from each session despite me having a faulty egr valve.






Edited by xylicon
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Here's what I found...


The final part of the entire smog test process is the functional inspection.

The functional inspection is conducted by the smog technician and is hands-on.

The smog technician will ensure proper operation of the following emissions components and systems.

A. Engine Ignition Timing
B. Check Engine Light
C. Gas Cap & Filler Neck
D. Exhaust Recirculation Valve (EGR)
E. Fuel EVAP Test (LPFET)

D. Exhaust Gas Recirculation Valve (EGR)

During the smog test your vehicle's EGR valve will be inspected for proper operation. This test applies to vehicles which are administered the "basic" California emissions test. your vehicle will not be driven on a dynamometer, and it's EGR valve will be manually checked.

How The EGR Valve is Tested - The EGR valve test process and what to do if your car fails or failed the EGR valve check.

EGR stands for exhaust gas recirculation. The EGR system recirculates exhaust gas back into the combustion chambers. Since these recycled exhaust gases have already been in the combustion chambers once, they have burned up most of their fuels, means there is now much less real fuel in the chambers to ignite. This keeps the chamber temperatures down and thus reduces NOx emissions. The EGR valve should be inspected to ensure its proper operation. A working valve should be able to open its passage using manifold vacuum.

Manifold vacuum is created during the engine's intake cycle. The high demand for air during this cycle creates a vacuum within the engine's intake manifold. This vacuum is then used to control several important functions within the vehicle, including controlling the EGR valve. Some vehicles even rely on this vacuum to control their heating and air-conditioning components. The EGR system is prone to collecting carbon build-up. Some vehicle manufacturers recommend cleaning this component an a regular basis. Please Click on "Under Your Hood" for more information on EGR valves and testing procedures.

The following vehicles are equipped with EGR systems - Acura, Audi, Buick, Chevrolet, Chrysler, Dodge, Plymouth, Fiat, Ford, GM, GMC, Saturn, Honda, Hyundai, Infiniti, Isuzu, Jaguar, Jeep, Lexus, Mazda, Mercedes Benz, Mitsubishi, Nissan, Peugeot, Porsche, Renault, Land Range Rover, Saab, Saturn, Subaru, Suzuki, Toyota, Volkswagen, VW, Volvo, and Winnebago.

Now, with all of THAT being said...

If you performed the EGR test IAW the FSM, then there shouldn't be a problem. I would take it back to them and WATCH them physically do the hands-on test to verify exactly WHAT failed.

I call Bull@!*%.

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Looks like you checked vacuum to the EGR valve, but I don't see a test of the EGR valve itself on that list. Pull vacuum on the EGR valve (I've heard you can push the diaphragm with your fingers, I just put a scrap vac line on it and use my mouth) and you should notice the engine stumble or at least change its idle as the valve opens. The passage between the EGR valve and the intake tends to accumulate carbon, and if that was blocked off, it would make the EGR not work even if individual components checked out.

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Pull vacuum on the EGR valve (I've heard you can push the diaphragm with your fingers, I just put a scrap vac line on it and use my mouth) and you should notice the engine stumble or at least change its idle as the valve opens.


Thanks for the suggestion Slartibartfast, that was actually the first thing I did before diving any further into the EGR system. I actually applied to much vacuum to the valve and the engine stalled, after that test I opened my FSM and checked the rest of the system, unless I'm missing something else I don't think there is anything left to do besides take it to another shop.

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Hmm. Yeah, if the solenoid is good and the valve is functional, I can't think of what else would be wrong, at least not that the smog check guy could've found without disassembling it.


Only other thing I can think of is I remember my '95 had a little short hose going to the BPT valve, and that hose was dry rotted clear through on the back side. I found it because a mechanic said he thought the valve sounded like it was fluttering. I never figured out what he was talking about and saw no change in operation after fixing the leak, but it's an easy thing to check anyway.

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I had to replace the BPT valve on mine because it was making that noise. It sounds like an exhaust leak under the hood, but it is not. My 95 has the BPT valve but my 1994 does not. So it may not be relevant to you.

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