Check engine light; is it transmission or engine related?


Hi, I have a 1998 Mazda protege LX, auto tranny, with 83K miles on it. lately transmission seems to have trouble shifting into 4th gear especially at highway cruising conditions (as judged from the rpm-tachometer). trouble would happen occassionally , and maybe stayed for a day and disappear the next. So I could not reproduce it to a mechanic.

Over the weekend the transmission would not go above 3rd gear again for 2 days in a row. Now the check engine light came on. Went in to Autozone and their machine gave a code P0703 - “Brake Switch B malfunction”.

Now I am not sure if this code is related to the transmission symptoms i described. but the thought of an expensive transmission repare scares me.

Can me anyone help me with this ? Thanks


First do your brake lights work?
Are they always on?
Sounds like you have a problem with your brake light switch (faulty, out of adjustment, etc.) or a loss of power to the switch (blown fuse, broken wire, etc.). I believe the trans issue is a direct result of the faulty switch.


sorry, i am not very knowledgable about cars. Can you explain how it is a direct result of the faulty switch. BTW, rear windsheild brake light has failed . but tail lights work fine


i just thought of another thing to look at. have any of your friends mentioned to you that your brake lights flash on and off when they are following you down the road? (have you noticed this on other cars in the past? not that it is related, just so you can figure out that there may be a problem)

if you are having flashing brake lights that IS an indication of a brake light switch out of whack.

you can hear the switch click on and off, as you apply the brakes. if you dont hear it, or if it is on all the time, thats the problem.

one other way to test this would be to go on a drive, when the shifting thing is happening, and and (while driving) pull up on the brake pedal with your left foot. see if that changes the way the shifting goes.

the spring which holds the pedal UP so the light goes off gets weak, and can let the pedal fall off the switch causing this also.


All P07XX are transmission related.
P0703 Torque Converter/Brake Switch B Circuit Malfunction is the full term I got,


yes that light can cause this issue. it may not be the light out perse’, but the cause of the light being out can cause this to happen. get the light fixed, then drive the car.


nope, havent seen brake lights flashing, nor did anyone tell me. but I’ll have my wife follow me and check your suggestions. thanks


That brake switch will cause your converter not to lock up and will overheat the transmission. What you are probably feeling is the converter clutch falling in and out of lockup. I would check it out further.



UPDATE: took the car in to a guy highly recommended on this site for Japanese cars. their scanner did not read any code. The mechanic test drove it though, and as always, the problem dissappears when its at the mechanics. Since he did not see any code , or see symptoms he did not want to take anything apart (honest guy!). now I am not sure whether Autozone guys are trustworthy ? just hate the thought of a shot transmission 6months later.