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Mazda 626 Troubles



  • Most of these should be covered by the Federal emissions warranty. (The oxygen sensors aren't - they're considered maintenance items - but they're a relatively small part of the total tab.) And they should be able to reflash the PCM rather than replace it outright, if there's a software error.
  • If your car can put out a P0421 code, then it has a bad cat. That code is not designated for any one particular year make or model. PCM's and converters are covered by 8year/80k miles warranty.
  • maxx4memaxx4me Posts: 1,340
    Thanks for the info. I called Mazda; they believe it is the O2 sensors since I am experiencing minor (very minor) bucking while driving and that the catalytic converter (CC) should not affect driveability. If the CC were bad (clogged) I would stall out or not be able to drive the car. I have emissions test next month. Perhaps the results will show if I'm running too lean or rich, thus pointing to the O2 sensors. Should I have both sensors replaced at once like my mechanic says to do, or should I have a Mazda dealer figure out which sensor is bad and replace the one?
  • I dont want to tell you that whomever you called is wrong, but they are. Code P0421 is a code specifically for cat effieciency. If either O2 sensor had a problem, there would be another code. You cannot get a P0421 code if you have an inoperative O2 sensor. The code, by its definition, tells you that both sensors are working exactly the way they should. Please dont waste your money on O2 sensors.
  • maxx4memaxx4me Posts: 1,340
    Thanks for the advice. The code explainations come off of the ALLDATA bulletins. Do you have any experience on the reliability of that firm's bulletins? While I have you on the line:
    1. my car "has some minor bucking to it". I was told that is a symptom of O2 sensors, not Cat converter.
    2. I was told that when the cat converter starts to go, I will not be able to start/run the car at all. Is this true?
    3. I will be getting an emissions inspection soon. Will the dynamometer test reveal any hints as to whether the O2 or cat is failing?
  • rotarykidrotarykid Posts: 191
                                                                          I am not familiar with alldata, but I can assure you that the diagnostic info I have is better because we(mazda) create it!Alldata is second hand info and is generalized.
     minor bucking can be a number of things. Spark plugs, wires, cap&rotor etc., all are prime suspects for such a problem. And it's not enough to just replace these parts with parts found at pepboys, you need OEM parts. The airflow meter on your car can cause hesitation and some minor bucking as well. Usually a code is present for that situation(P0171). O2 sensors could cause similar problems, but again, a code would be present that tells you the sensor is bad before you could ever notice a problem.
    A clogged converter will inhibit performance, but any problem that would cause a clogged converter(typically raw fuel entering the exhaust) would cause a check engine light to come on for whatever reason the fuel was getting by. Unburnt fuel would mean a misfire and each cylinder is monitored for that scenario.
    If the converter becomes worn out-and they do- it is possible that you would never have a drivability problem at all. Whats taking place in the converter is only for emmissions purposes, and does not affect actual engine performance. However, if the cat is bad, you will not pass an emissions test. The code P0421 tells you that the cat is not performing properly and it needs replacement. This is why in the near future various states that have an emissions testing program will do away with sticking a tube up your tailpipe and will only be looking at the cars computer. These cars monitor themselves. The test station will check to see if your car has any of the code #'s present that fall under the federal or state guidelines for emissions failure and then you will have to make neccessary repairs. Dont think about having the codes erased and running down to the inspection station because that will not work. Your vehicle knows when its codes have been cleared and knows it needs ample time to recheck itself. Until all systems have been rechecked, it puts out a P1000 code that indicates more time is needed to perform tests. Your car will not pass any state or federal program's test with that code.
    hope this helps and try to remember that the corner garage is way behind the dealers diagnostic capabilities.
  • dmaizedmaize Posts: 7
    I go to my Mazda dealer tomorrow AM to have my 97 626 evaluated. Thanks for your info on the PO421 code. It sounds like I can go in confidently knowing that, because of the PO421, I have a bad cat conv that is covered under the 8/80K emissions warranty. My question to you is to determine the meaning of my other codes: PO171, PO1130 and PO300. My mechanic told me that PO171 is a overly lean code, although you commented that it is airflow-related. PO1130 appears to be 02-related; is that true? Could it be that all of the above codes are connected to the bad cat, or do you think it's likely that there are other culprits? Lastly, are there any emissions-related parts other than the oxy sensors that are not covered under the emission warranty? Thanks for your help here!
  • rotarykidrotarykid Posts: 191
    the P0171 does indicate a lean running condition. The airflow meter has been the main cuase for this particular code for quite a few years. The sensor becomes contaminated and puts out bad readings for the pcm. There is another major cause of P0171 however, and that is an intake gasket leak. This is easy to find if your mechanic has any skills at all.
    The P1130 code indicates that the pcm is trying to compensate for the lean condition but cannot correct it. This code is a result of an O2 sensor not switching, but it seems to be working as it should. In other words, the O2 sensor is doing something that it shouldnt be doing, but only as a result of another components failure. Most likely the air flow meter. A clogged fuel filter or injectors have also been known to create extreme lean conditions so make sure your filter is/has been changed.
    P0300 indicates a random misfire and can be a result of an extreme intake gasket leak in one area.
    Without the proper diagnostic equipment or the knowledge to use it, these codes could have your mechanic selling you lots of parts you dont need. I cant stress enough that the dealer is the best place to bring you car for such problems. I see so many cars come in with aftermarket O2 sensors and similar items, and then the customer has to pay me to diag it properly and put in the correct parts.
  • on my 1995 mazda 626 4 cyl the tranny is slipping in all fwd gears. i disconnected the hose going to the radiator cooler and installed a clear tubing between the connections. the tubing is 5 ft. long. i had the front wheels off the ground and started the engine. i placed the selector in all ranges and revved the engine to 2000 rpm in each postion and noticed that the tranny fluid only traveled around three feet of the tubing. the filter is internal on this tranny. could this be the pump or would a tranny overhaul kit be the answer. has anyone had this problem? if so what was the solution? you can e-mail me at [email protected] thanks john.
  • maxx4memaxx4me Posts: 1,340
    Well, I turned off the CEL and passed emissions with flying colors. My readings were very low. I guess the P0421 code truely is indicating an initial problem with my cat converter. If it were the O2 sensors, I would assume that it would indicate so in the readings. I guess I'll get the cat fixed when my car conks out.
  • My wife has a '96 626. The "check engine light" came on today, what can (if anything) I check before I take it to the shop. Had a 200SX Nissan w/same problem, replaced the O2 sensor and that was that ... can ay one help? please e-mail me at [email protected]
  • As usual, I'm turning to all you guys to see if you can advice...

    My 95 L4 626 ATX with 85K miles has consumed ~1 quart of oil since it's last oil change (5K miles ago...). I have been using Valvoline full synthetic in the last 3 oil changes (~15K miles). The strange things are:

    a) It had never conusmed a drop - The dip-stick was always near the full mark before each of the previous three oil changes.

    b) I have not smelled burnt oil since I changed the valve cover gasket a while back, and I cannot see any oil smoke coming from the exhaust. There are no leaks in the driveway either, and the collant has no oil.

    c) The car is running great, and neither my wife or me have noticed any lack of power, etc., etc..

    After looking on the web, my only (cheap) explanation is that I made a big mistake by changing the Mazda PCV valve with an aftermarket 3 dollar item right before the last oil change. Aparently these are the cause for increased oil consumption due to the flakiness of the aftermarket PCV valves.

    Could this be the case here, or should I start preparing myself for more trouble down the road?

    Many thanks in advance,

  • maxx4memaxx4me Posts: 1,340
    As a driver, not a mechanic, I can only offer the obvious: have someone else start the car in the morning while you stand behind the car to see if there is any plume of smoke. I had this problem with my toyota, but could not see the smoke from the driver's seat.
  • Maxx4me, I actually know there's no oil smoke coming out because I have watched my wife leave the dirveway several times. The only thing coming out the tail-pipe these days (it's cold in Philly) is water vapor which rapidly disipates. Plus, once the car is warm nothing comes out the tail-pipe (I actually left the car running and went and checked it...).

  • Sounds plausible to me. Generally, when oil consumption rises, it tends to leave calling cards. And generally these engines don't use a lot of oil even at relatively high mileages - my '93 never had any unscheduled oil additions, though admittedly it got 2500-mile oil changes.
  • could somebody tell me what causes the surging problem on my turbo 626, it's an intermittent problem, and when it does happen, it goes as high up to 2000rpm from regular idle speed in couple second intervals? the car has about 80,000 miles on it now, thanks
  • Has anyone had a problem with rust forming or bubbling up under the paint? I have a 99 ES V6 AT with 49K. According to Carfax, it has never been in an accident and I am the second owner. It is on the passenger side near the top of the A pillar and on the driver's side on the rear quarter panel. Both spots are approx. the size of a half dollar. I can't seem to lay my hands on the warranty info. Any help would be truly appreciated.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 62,410
    Your car could still have been in a serious accident, or multiple accidents, and not have that show up on CARFAX. CARFAX only reports totalled cars from public records. I bought a used Miata that had $18,000 in collision repairs and showed up clean on CARFAX.

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  • I just got a 2000 626 LX. Check engine light on within 24 hrs I got it. I know nothing about car. I was so upset and disappointed. Can I drive back to the dealer near 100 KMs away or I got a nearby Mazda dealer checked. I was told this is usually not covered in limited factory warranty, it maybe sth wrong with emission. Will this be a repeating problem? I saw lots of cars have this problem. Any help will be truly appreciated.
  • maxx4memaxx4me Posts: 1,340
    You certainly can take it to any Mazda dealer. I would ask them first what types of things will be covered before they diagnose it. If they tell you that the problem might not be covered by your warranty, then you have to choose whether you want them to read out your code or not. My mechanic does not charge me for reading out the code on my 626; the dealer will. My mechanic also provides much cheaper rates (and performs much better repairs) than most dealers would. Therefore, if it were me, I'd first take it to Mazda near your home and ask lots of questions about what is covered and what is not. You hopefully have a good relationship with a local mechanic who you know will steer you right in case you decide to opt out of the dealer option.
  • Here are the instructions for programming new remotes. I know they sound wacky, but it really does work.

    1. Sit in the driver's seat, driver's door open, all others closed.
    2. Do this three times: insert key, turn to "on" position, turn to "off" position, remove key.
    3. Push the driver's door ajar switch three times. Car will chime.
    4. Push any button on the 1st remote twice. Car will chime.
    5. Push any button on 2nd remote twice. Car will chime.
    6. Wait three seconds. Press door ajar switch one time. Car will chime.
    7. Remotes are now programmed.

    Note: Any previous remotes will no longer operate on this vehicle.

    I hope this helps.
  • To All,

       I posted message # 1395 to this board back in January and the outcome to that inquiry was that the dealer I purchased the car from replaced the PCM at no charge because my 2000 626 V6 was still just under the warranty period at 49,500 miles.
    The dealer stated that they could not get any error codes or get the car to start so they just replaced the PCM to get it running again. The first week of March, the car stalled again on the highway. This time I was able to start it (after several tries) and made it to work. I went out after work to start the car and it would not start. The next morning I had the car towed to the dealer again. At the dealership they were able to start the car and they kept it for 4 days.
    The mechanic at that time told me that he could not re-create my problem and without any error codes, had no idea what was wrong with my car. Comforting thought huh ? Anyhow, I picked my car up again and this past week, the check engine light came on and the car started to run rough and felt like it was trying to stall out again.
    Back to the dealer for a THIRD time for the same problem ! This time I was told that I needed the
    Idle Air Control Valve & Gasket the tune of $ 650 !!! You see, now my vehicle has 54,000 miles and is out of warranty. I argued that the problem first occurred while the car was still under warranty. Mazda has finally agreed to pick up the tab for the part, BUT the dealer wants to charge me $ 160 for the labor. They are also telling me that I won't get my car back for a week because they need to wait for the part and that a loaner car is not available. Is this how any of you other Mazda owners are treated by your dealership ??? A friend of mine told me that this should be covered under an emissions warranty - that this warranty runs for a longer period of time & miles...does anyone have any specifics on the emissions warranty for this model ? Is this a common problem on these vehicles ? Thanks everyone for your help !

  • maxx4memaxx4me Posts: 1,340
    I don't believe anything is covered beyond the 50,000 mark except the catalytic converter (80,000). I had a similar problem to yours. Mazda did the warranty work even though I was over the 50,000 mark because the problem started within the warranty period, and was documented by the dealer. They also gave me a rental car and did not charge me any labor. A favorite trick of mine (and I do it quite often), is to get REAL LOUD when you are at the dealer. Make sure lots of people are around. I often get my way in order for them to get me out of the place (and not take any other patrons away from them). As I have done, just remember these times once your warranty/extended warranty expires. You need to be thinking of what your next car will be, because there are still lots of bills ahead of you my friend as long as you own this Mazda. I still have my '96 626, but will donate it away before it has a chance to leach real cash out of my wallet. I suggest you do the same.
  • I am curious though...was it Mazda or your dealer that picked up the labor cost & the rental car ???
    How many miles on your 96 now ? Have you had any other problems with your Mazda ?


  • maxx4memaxx4me Posts: 1,340
    Hi Jim. I don't believe the dealer EVER picks up the cost. They pass it on to Mazda. That certainly was the case with my O2 sensor problems. In fact, it amazes me how quickly these dealers will screw their parent company out of money. I can honestly say that there were repairs done to my car which probably were not necessary. As for problems with my '96 (87,000) miles, I would probably take up 2 pages with problems. Let's just say, I put $3,500 of repairs on my $650 extended warranty. Some of the highlights included: strut top bushings, 2 radiators, rack and pinion steering, master cylinder, 2 additional transmissions, water pump, timing belt...About the only thing I have paid out of pocket for was I decided to put on 4 new struts. Although they were leaking, I decided to not file a claim since I was right at the end of my extended warranty and I figured since I had not had a total breakdown, they would not go for that one. Currently, my check engine light is coming on since the catalytic converter is beginning to fail. I won't replace it until it does. Also, my engine mounts are beginning to weaken. Again, if you have a paper trail showing that your problem started before your warranty ended, I would either do the screaming thing, or call Mazda directly. Trust me, your dealer won't want you to do the latter; so make some noise either way.
  • tyguytyguy ColoradoPosts: 1,219
    Hello all. This is my first post in this particular forum, and it's for a friend with a '99 626 LX 4 cylinder automatic. The car currently has around 75,000 miles.

    The main symptom is severe engine stumbling and hesitation at idle and when accellerating. The check engine light comes on occassionally, and the codes indicate too rich a fuel mixture.

    The car was taken to the dealer three times, and each time the mechanics replaced the spark plugs and the spark plug wires. The #1 plug was consistently carbon fouled every 6 months. New wires and plugs would help for a short while.

    The problem has gotten much worse. The plugs foul within weeks, and all the chambers are effected. The new plugs only lessen the hesitation now.

    Over the weekend I checked the color of the spark on the plugs, and noticed it was orange rather than blue. I swapped out the coil with a new one, but it didn't help.

    Any ideas on what is happening?

    Tesla Model 3, 2015 Subaru Outback, 2013 Audi A4
  • purifyerpurifyer Posts: 5
    My '91 626 overheats after a while. The electric fan is not coming on. Is there an easy way for me to check if it's the fan motor or the sensor? I'm running this on a low budget. Thanks.
  • rotarykidrotarykid Posts: 191
    The carbon buildup on the plug/wire is the most common cause of hesitation on the 99 and up 626 four cylinder. It is important to replace the plug and wire of the affected cylinder that is misfiring. From what you wrote, this was done on multiple occasions. A bit of information would help more...what was the code/codes that were retrieved from the cars pcm? Also find out if the timing belt has been replaced and that it was installed properly. There is a recall for 97-98 626 timing belt tensioners being faulty and as a result cause slack in, and eventually failure of, the timing belt. This can cause hesitation and poor running. The recall was limited on paper to certain 97-98 626's, however, mazda failed to recognize all the cars that it applied to (mostly 98s) and as a result there are cars being brought in all the time with no open recalls yet have the faulty tensioner from the factory. It wouldnt surprise me to find some 99's that might have the same problem.
    As for whats covered above and beyond the 3yr 50k warranty, the catalytic converter and the PCM are all covered up to 8yrs or 80k miles.
  • tyguytyguy ColoradoPosts: 1,219
    Thanks for the advice, rotarykid. Unfortunately, my friend didn't record the code numbers when the dealer pulled them. I'll have to wait to learn those until the next time he takes it in. I'll be sure to warn him about the belt tensioner issue.

    I think I may have found the root cause of the problem, though. I searched some of the Technical Service Bulletins (TSB) yesterday and ran across SB614906, which can be found at

    The TSB states that rough idle and hesitation during acceleration on '98 to '01 626s can be attributed to a leaking intake manifold gasket. The symptoms identified in the TSB match what is happening with this particular 626, and the VIN number falls under the ones covered by the TSB. Since this TSB was issued on 10/18/00, and two separate dealerships identified and documented the problem but failed to fix it properly while under warranty, my friend is going to insist the TSB be performed without cost. I think he has a good case.

    Tesla Model 3, 2015 Subaru Outback, 2013 Audi A4
  • rotarykidrotarykid Posts: 191
    and the leaking intake gasket is very easy to determine. I would be surprised if ANY mechanic missed that. The code P0171 goes along with the problem.
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