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I Just purchased a 1992 Mazda MX-3 GS with the 1.8 V6 engine and the check engine light is on.

I checked the diagnostic codes and it looks like i have codes 15, 16, 17, and 23

15 LHO2S inactivation error
16 Exhaust gas recirculation (EGR) system
17 LHO2S inversion error
23 RHO2S inactivation error

The PO told me that the O2 sensor in bank 2 is throwing the check engine light but i really like to look into things myself before i just go out and buy stuff.

So can anyone help me with what is wrong and if it is only one thing, why is there 4 codes?

Thanks for all of your help!

Congrats on your purchase and welcome to the forum. You found a good forum for these somewhat rare cars.

Check out the service manuals here.

You've got codes from both O2 sensors (left and right). Left is code 15 and 17, right is code 23. Codes are specifically in the manual beginning here.

Left side of engine is closest to the bumper or radiator. You have 2 O2 sensors on your car 1 in each exhaust manifold.

EGR code might be fixed by pulling the EGR valve and cleaning it. Only problem is that it is hard to get to. Usually you need to remove the intake manifold to access the EGR valve. The EGR is under the throttle body on the engine block and attached to an exhaust pipe.

Get some universal Denso O2 sensors (part# 2344209) from a place like Rockauto and splice them in to save a few bucks. That should solve 3 of your codes and improve gas mileage a bit.

Reset the ECU (bottom of page F2-78) and see if the EGR code comes back. EGR is nuisance and probably not worth the effort.

OK, so start with both O2 sensors and then check the codes again.

Thanks for all the help and a quick reply!

If the EGR code is still there, will it do anything bad to the engine? It has to have some adverse effect when it's not working properly

Start with simplest things first. Clean/replace air filter, fuel filter, replace spark plugs (use NGK brand), new disty cap/rotor. Usually a tuneup will solve many problems, hesitation, stalling, poor gas mileage, even check engine codes.

EGR recirculates exhaust gas under certain conditions. Recirculating exhaust gas is done to reduce NOx emissions. Because exhaust gas is flowing through the EGR valve it can get clogged or stuck open or closed due to carbon buildup. Our EGRs are vacuum operated based on signal from the ECU. The ECU checks the position of the valve and sets a diagnostic trouble code if the position signal is not what is expected. Code could be due to bad position sensor, broken position sensor wiring or bad connection, bad vacuum hose or a stuck EGR valve. If EGR is stuck open you can have a bad usually very low idle. Often the code will be intermittent because the valve is simply sticky not consistently misbehaving.

Ok, so i was looking for a detailed write up on how to properly clean the egr and i can't find one. I have minimal time this weekend and after i change the O2 sensors, and the EGR code is still there, i'm gonna need to start working on it ASAP. So i was curious if anyone has wrote something on how to properly disassemble and clean the EGR.

Thanks for all the help so far! It's greatly appreciated!

Hi new member,
I also have a red, '92 MX-3 GS and had the same codes. I just put some black electrical tape over the dash board so I can't see the lights flash any more. Probably NOT the answers you were looking for... Thank goodness there are folks on this site who can offer real advice! - Steve

egr shouldn't effect the engine much unless you have to go through emissions but o2's will effect gas millage do what davmac said or even try reseting your ecu then see what comes up again

BornSticky wrote:egr shouldn't effect the engine much unless you have to go through emissions but o2's will effect gas millage do what davmac said or even try reseting your ecu then see what comes up again

Actually EGR can cause crappy idle and take off like davmac was saying. The bolts to remove it can be a biotch and as far as cleaning just use something like brake cleaner. I used SeaFoam twice and it got rid of my sticky EGR,,,for a time. Ineveidabley your going to have to remove it or pay to have a professional injector leaning done that may also clean your EGR.

So I went down to my parents place this last weekend cause they have more room to work on the car. As i was leaving my house, i checked the oil and coolant and the coolant was low... I topped it off and headed home and when i got home, it was low again. After some looking around i found my water pump to be the culprit.

I headed down to the auto store and picked up a new air filter, oil filter, oil, coolant, water pump, timing belt, and both O2 sensors...

About $400 later i got my car all jacked up and started working on it. I bought the universal O2 sensors cause i can't afford $120 for one O2 sensor... After doing all of the work on it and getting the O2 sensors wired up, started it up and it runs like a champ. After driving it back home when it was colder than usual outside, it took a little while for the car to warm up. Should've done the thermostat while i had the coolant drained.... Should've thought about that ahead of time but i guess i'll just do it in 2 weeks when i clean the EGR.

After clearing the check engine light, it came back on again. I didn't get to check it out but i'm assuming that it's still the EGR. I will check it here in the next couple days to make sure my O2 sensor codes disappeared but everything went smooth with the wiring so i don't think those are the problem.

I'm just going to keep plugging away till i get all of the little problems taken care of. It was sitting around a lot in storage so there is some work to be done.

Also, if anyone has stock height suspension springs, could you please PM me. The PO put lowering springs on it and although it handles amazing, lowering just isn't much of the look i want. Full Coil Overs will probably be coming in the future but i need it raised before winter and putting all of this regular maintenance into it is making me low on funds...

I figure i'll clean the EGR and replace necessary gaskets, replace the thermostat and make sure everything is tip-top after that, and then put the new/used springs in the suspension and then start saving for next summer!!! I have too many things i want to do including the KLDE swap

Congrats on the successful repairs. Carburetor cleaner or throttle body cleaner should do a good job on the EGR. I've heard that soaking it overnight is good but never took the time.

I'm all out of carb cleaner, i went through over 6 cans working on my 1979 XS1100 Special...



I doubt i'll have time to soak it unless i can't get it cleaned well enough... In which case i'll have no choice but to soak it.

While trying to fix the water pump, the water pump tensioner was being stubborn and i ended up wrecking it. I found a used one at a junk yard in Wisconsin for $60 shipped but they're not sure if they have it. They're looking into it now and they're gonna call me back.

Parts are hard to find for these things...

Now i think i'm looking for a water pump tensioner and stock suspension springs for my 92 MX-3 GS.
The water pump tensioner is definitely more important..

As soon as the guy from the salvage yard gets a hold of me, i'll end up putting a Want To Buy ad up on this site and see if anyone here has the correct parts.

Is there anything i should plan on replacing when cleaning the EGR? Anything besides the intake gasket and EGR gasket?


Update: The junk yard only had the 4 cylinder model so i put a WTB add up in the proper area if anyone can help me there!

FYI same tensioner used on all KL engines so look at 93 - 97 Probe GT, 93+MX6 LS, 626 and Millenia w/ KLDE.

What exactly do you need for your water pump tensioner (whole bracket, adjusting screw, pulley)?

I need the whole bracket. I'll look on car-parts.com again and check for some KL engines and i'll get back to you!