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Eric, Automotive Repair Shop Manager
Category: Mazda
Satisfied Customers: 32537
Experience:  20+ yrs. experience as repair shop manager and technician.
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My 2008 Mazda CX-7 alarm control works. But when I want to

Customer Question

My 2008 Mazda CX-7 alarm control works. But when I want to start the car, the switch won't turn... And car won't start. I tried switching out the battery and then it started to work. Then the next day, same thing, it doesn't want to open the switch. There's
a symbol on the car with a key in it that flashes. I don't know what is wrong with this
Submitted: 2 years ago.
Category: Mazda
Expert:  Eric replied 2 years ago.
I am sorry that you have not been helped yet. I just came online and saw your question
If you have a spare key try it. If it works, then your primary key is faulty. If the spare doesnt work, there is a fault in the immoblizer unit that is preventing it from reading and accepting the key.
Customer: replied 2 years ago.
I don't have a spare key. Ever since I had the car, I have never had a problem turning on the car.
Customer: replied 2 years ago.
Like I mentioned... This Bart happened the other day. I tried switching out the battery and worked a few times. But now it doesn't want to work again
Customer: replied 2 years ago.
Barely* happened
Customer: replied 2 years ago.
The battery that I had swapped out was from the alarm control.
Expert:  Eric replied 2 years ago.
Based upon the symptoms including swapping out the battery for the alarm control, either the reciever is faulty or the control module is faulty. Only way to know which is to test them for communication and commands with a scan tool.
Customer: replied 2 years ago.
How could this have gone faulty? I've never had a problem with this. The problem first started because initially, my control had low battery so it wouldn't pick up the signal that the control was in range in order to start the car. Then I swapped the batter and the problem was fixed. But now there's a different symbol, which is the car and key symbol that lights up now
Expert:  Eric replied 2 years ago.
These are electronic components. Circuit boards fail, solders break, and in the case of the control module, software can fail from glitches or harddrive reading errors. Just like a tv or dvd player or laptop can suddenly fail without obvious cause, automotive electronics can as well.
The symbol is for the immobilizer system(antitheft). If the receiver or control module fails, it will turn on the light and prevent vehicle from starting. The control module is most likely the issue due to software failure that is causing it to lose memory for the key recognition.
You can try removing the battery for the fob and reinstalling it to see if it will recognize the key again. But even if it does, this will still need to be addressed as something in the software is causing it to lose memory
Customer: replied 2 years ago.
now what should I do since the car won't turn on? The dealer wants me to bring it in but that's going to be a lot just for the tow.
Expert:  Eric replied 2 years ago.
To repair yourself, you would need a high end scan tool that can do tests and programming as a new control module would require programming. you can buy these. The average cost for one is around $3500. So it is cheaper to have it towed and repaired by a shop.
Like I said before, you can remove the battery and reinsert it and see if it will crank. If it does, then you can drive it to a shop for the needed diagnostics.
Unfortunately on today's vehicles that have well over a dozen computers on them, unless you have a high end scan tool, there is quite alot that you simply cannot diagnose or repair at home. and in the case of an immobilizer issue, there are no workarounds to get it started.