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Randall C
Randall C, ASE Master Tech
Category: Mazda
Satisfied Customers: 12803
Experience:  ASE Master Certified, 35 yrs, Diag/Electrical Specialist
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Ew, I've got a 2005 Mazda 3 with the following codes-P0745,

Customer Question

Hi Drew, I've got a 2005 Mazda 3 with the following codes-P0745, P0753, P0758, P0763. Transmission goes immediately into limp mode. Have checked and cleaned connections at trans and wiring harness. Codes return immediately. Dealer is saying PCM needs replacing but I am not sure that is the case.
Submitted: 1 year ago.
Category: Mazda
Expert:  Randall C replied 1 year ago.

Hello, all the codes pertain to a control problem at most all the trans solenoids as well as a the pressure sensor, This in fact can be a bad PCM but,, test must be done to help confirm.Unsure how handy you are but step one is checking /cleaning terminals at both Trans and PCM,If certain BOTH are good? you ten have to unplug the trans AND the PCM and check all wires between the trans and PCM for shorts to ground, meaning, look at the diagram I have included, start at one end /wires between PCM and trans, BOTH unplugged, Use an OHM meter and probe at the PCM connector one wire at a time, to see if short to GROUND, so, one lead goes into harnes, other to the NEG terminal of battery, continuity? then a short and harness needs changed, ALL test ok? then suspect PCM has failed, These are the basic tests, Other test require getting to all the solenoids in the trans, I lkean to harness, PCM possible

Customer: replied 1 year ago.
Looks good. I'll check it and see. I'm actually wondering if this could be a ground issue after seeing the diagram,. Don't have any history on the car.
Expert:  Randall C replied 1 year ago.

well, possible. Thus whay I sent diagram to you, The thing is, all the solenoids and the sensor are grounded each on their own per say,, You for sure have to check the ground(s) showing in the diagram