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BigBob, Shop Manager/Technician
Category: Car
Satisfied Customers: 4838
Experience:  Shop Manager with 25 years experience
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2004 mazda: speed sensor..automatic transmission..the AT light comes

Customer Question

Is there a way to test the sensor(s) related to the code P0715 input/speed sensor circuit malfunction on my 2004 Mazda3 2.3L with an automatic transmission? I unplugged and reattached the sensor wires below the battery box and I unplugged and reattached the wire harness below the glove compartment; should I disconnect the harnesses by the battery? It still occasionally will lurch & start to limp; the AT light comes on. What is the name of this sensor (and the other along with its location) so I can buy them if necessary? I am not sure if it is related; however, I installed a power steering pump and had to splice the small (7) wires going to the pump (the two big red and black ones were intact and seem alright). We had the dealer reprogram the power steering pump and it works; however, they said it triggers the CEL due to high resistance. The Codes I read are for the knock sensor which is seemingly unrelated. As soon as I start the car, the knock sensor code returns. Any suggestions?
Submitted: 8 years ago.
Category: Car
Expert:  BigBob replied 8 years ago.

The code po715 refers to the Input/Turbine Speed Sensor. This is the location. The only way to test it is with a oscilloscope. You will have to measure the square wave signal. Check it visibly and make sure it does not have any water intrusion or connector damage.



Good luck,
Customer: replied 8 years ago.
Thanks for the diagrams; however, I am not sure what your answer is. Is there only one sensor called the input/turbine speed sensor? I thought there were two associated with this code and from your diagram it could be a VSS which also has a gray connector? I assume each is tested with a scope and so it is easier for me to replace one (or both) if you think both are capable of producing Code P0715. My guess is the one below the battery box, with the gray connector which I think is the input/turbine speed sensor.

What about the other code the dealer claims is related to the Power Steering pump wiring and not the knock sensor code my code reader suggests? I realize a Mazda dealer may have more focued equipment. Is this what you think. To me, getting several codes in a short time seems curious to me. It just seems strange to have to replace the entire engine wiring harness when we should be able to get comparable wires to carry the current.

Please follow up when you get a chance; I will look for your answer tomorrow.
Expert:  BigBob replied 8 years ago.
Po715 is a code designated to the input/turbine speed sensor only po720 is for the vehicle speed sensor. Vehicle speed sensor would set a different code. If you are going to change any sensors I would change that one first. There is a vehicle speed sensor (see previous picture) but that would set a different code.


As far as the knock sensor code that does not sound right, I would have to look at the schematics to figure ot out.