Mazda99Nikon

My 1994 has only sporadically flashed code 16 - EGR system malfunction light but now it seems to come on more often.

In searching EGR I found several fixes. I was wondering what your all thoughts are on these?

1. EGR function Sensor Bybass Circuit with Radio Shack relay. Looks like a simple fix until you have to track down the four wires to make it work. Can this be accomplished by splicing the wires in the passenger compartment where they come off the PCME?


2. Changing to a 1995 PCME. Will this really work? In previous posts other owners reported switching out the Calif emissions PCME with the nationalized one, but I've already got the nationalized 1994 N3C1 Fed. MT and it still throws the code. I'm not sure if using the 95 PCME would actually solve the problem.

3. Replacing the EGR gasket with part number N3A1-20-305A. Anybody around here actually done that and found it to work?

Kind of leaning to option 1. What are your thoughts?

Mahjik

iTrader: (1)

All US based 94 ECU's have the electrical EGR. The 95's and the non-Cali 93's ECU's do not.

Mazda99Nikon

Thanks Mahjik.

Here's an interesting fix ... I went out and did three really high speed runs this afternoon testing the 10-8-10 sequence and the engine light went out and has stayed out. Reset the ecu by removing the negative battery terminal and the light still stays out.

The car had not been driven in over a year, could just getting it some decent exercise help with this issue? Maybe the EGR valve was just sticky?

hyperlitenerd

iTrader: (1)

I would get my code 16s when ever I would drive slow, low rpm shifts, no turbo. Then it goes away pretty quick when I would beat on it for a little bit.

aldos93

iTrader: (1)

Mine is quite the opposite.. It goes on when I give it some go. Weird. What does it all mean!!?? lol..

Monkman33

iTrader: (28)

It means it's time to get rid of it.

aldos93

iTrader: (1)

I need it to pass smog though. Do you mean get a new one?

purerx7

iTrader: (61)

I had the same problem as you, swapped to a non-egr ecu about two years ago and have not had any problems since. You can get used ECU's from people who go to standalones for about $50 here on the forums.

Speed of light

iTrader: (8)

This was a common problem with these cars, and mine had the problem from the time it was new. (93/Cali) The dealer replaced the EGR valve several times under warranty and it would fix the problem for a while, but it would always return....

The work-around or permenant fix, if you will, was a small circut I made to trigger the ECU's EGR sensor input whenever the EGR output was activated. Never saw a code 16 again. Others' on the forum have used a small relay to accomplish the same result. If you eliminate the EGR valve altogether and retain the stock ECU, then you must use this simple work-around to prevent a code 16.

Good luck.

aldos93

iTrader: (1)

Yeah but I still need it to pass smog.. If I take it out all together, or bypass it like you guys are suggesting then my NOx will still remain high, and in the end will not pass my car. right?

RLaoFD

iTrader: (6)

I remember when I had a wideband in place of my o2 on the DP the stock ecu threw a 16 code. Perhaps if you could find out if your o2 sensor is okay that may be the problem. I don't know much about the electrical system so I may be wrong. Just linking patterns from my own car.

aldos93

iTrader: (1)

oh right on.. yeah any help is great. thanks.

j9fd3s

iTrader: (3)

#3 gasket was updated to that number in the 90's, you car probably has it already, does not seem to fix anything.

#4 the egr passages are teeny, and have zero impact on emissions done in a state test. the federal EPA testing is different than any of the state tests.

RLaoFD

iTrader: (6)

Smog test cannot be done w/ a check engine light throwing a code.

Monkman33

iTrader: (28)

the fix for the code has alrady been discussed in this thread. ^^^

Get rid of the egr. use a block off plate. wire in the fix. done.

beckrx

iTrader: (18)

My 94 was having the same problem. I initially replaced my EGR valve and that solved the problem until I performed a complete vac tube replacement and replaced all solenoids then the code reappeared. I replaced my 94 ECU with a 95 ECU (CA) and it solved my problem. $50 for the part and 5 minutes to install.

aldos93

iTrader: (1)

That's ridiculous the egr valve makes no difference in smog emissions. Why even have it then? So dumb. Anyways, thanks for the help.

I_want_all_the_tacos

Sorry to revive a dead thread, but thought I would add a potentially useful, recent data point here rather than start a new thread.

I have a 94 manual California Rx-7 (N3A3) that needed a smog (emissions) test done in California. I was recently having issues with the CEL code 16 EGR problem and spent hours pouring through all the potential fixes in this forum (thanks for the plethora of info!). For my situation, my car only has ~50k miles and is driven a small handful of times a year so I don't really care about the EGR valve and the pros/cons of blocking it, I just wanted the cheapest, easiest, and least labor intensive fix for getting the car to pass smog check. I decided to go with the ECU swap method and picked up a 93 Federal ECU (N3A1) from this forum's classifieds. I just want to confirm for anyone in a similar situation, maybe decades from now, that this indeed solved the code 16 issue. No more check engine light, and no changes to car performance like idle stability. I didn't do anything to the EGR itself. The car successfully passed the California smog check.

Some notes about the actual emissions testing since it is fresh on my mind. I had to use a STAR certified test center. I actually just had my daily driver (07 BMW 328i) put through a smog check at the same center a couple weeks ago and that one was super fast (< 15 min) and hardly required the tester to do anything to the car. I didn't realize that as of today (09-03-2020) the current California requirement is that cars older than 2000 have to be put on a dyno and thoroughly tested under load. This test way was more involved (> 20-30 min) and had many stages of testing. My previous code 16 issues were sometimes intermittent as others in this thread stated, and often times when cold and just idling it wouldn't trigger the code. So I had an initial temptation to just risk it and try to pass the test without doing any fixes. However, after observing the actual test there is no way my car would have passed without the ECU swap as the test itself would have certainly triggered the CEL. Bottom line, ECU swapping to a 93 Federal (and others have stated any 95 models) will solve the problem and will allow your car to pass emissions. My only note regarding the ECU swap is be prepared to struggle with the cable connector latches. Some of them were practically glued shut. Best method I found was sticking a flat head screwdriver down into the connector's middle release point and simultaneously leveraging the screwdriver to push the cable outward. This worked better than trying to just push down on the release and pull the cable out with my hands.

DaleClark

iTrader: (55)

Thanks for the update! Yeah the ECU swap is a cleaner and easier way to go on a stock or near-stock car. Especially since stock 93 ECU's will be plentiful and cheap.

I think newer cars they can just hook up to OBD2 and the car will tell it "I'm OK" and that's all they need to pass. Older cars I think they load up since the ECU's aren't as comprehensive, the FD ECU for sure isn't with no OBD2.

Dale

I_want_all_the_tacos

Yup, that seems to be what I learned when looking into the details of the testing. One thing that is nice is that the actual acceptable emission ranges are set by your specific make/model/year car. So even though we have much tougher modern emissions restrictions, when they run these tests they are still only expecting your car to be at a certain standard for what your specific car should have been capable of at the time it was produced.