Hello, Guys! New here and looking for advice on an issue.
I have a 2016 Mazda 6 with 66,000 miles having troubles.
I had a battery that was getting weak, cranking slow in the morning but still starting up and running OK. Then it got cold and last week and on the way home I experienced a check engine light and a loss of nearly all power. Limped home (barely) and got out my simple OBD II code reader. Codes P0171 (lean condition), P0302 (Cylinder 2 misfire), and P0300 (random misfire) were seen. At that point I was not yet thinking the battery could potentially cause those so I switched the coil packs on 2 and 3, and also tried a brand new coil pack on 2 and 3 and changed all spark plugs. Same codes coming up.
Next day the battery was too weak to crank, so I got a new battery and cleared the codes. It started up and the engine got a lot of power back, but still ran really rough/smelly and the same codes came back along with a new one P0600 (serial communication issue). I then tried to reset the PCM/ECM by ways I could google (disconnected the battery and jumpered the terminals, tapped the brake 5 times, held the brake and horn to discharge the PCM, etc.). No luck, so took it to the indy up the road. They checked the mass flow meter and said it looked good and suggested that what they would try next was to replace all four injectors at a cost of $2000. Nope. Not yet, at least.
I picked up the car today and drove it for about 15-20 miles to see if I could get the computer to relearn. This time the codes that came up were P061B (problem with torque monitoring system), P0102 (mass-air flow circuit - looks like the indy did remember to plug it back in - I checked), P0113 (air intake temperature sensor), along with the previous codes P0302, P0300, P0171 and P0600.
Sooooo, yeah that is a lot of codes and its making me wonder if I should try replacing the PCM. Seems unlikely all those components would be having issues at the same time, so I am wondering if the thing has gone haywire. Maybe it got hit with a voltage spike when I hooked up the battery?? Trying to decide if I want to try a refurbished PCM, try the new injectors, or just take it to the dealer. Maybe someone on here has some recommendations? I may try a few simple things in the meantime to rule stuff out (compression test, spark gap test). Any guidance would be appreciated!