Just got a used 04 Mazda6 automatic 6 cyl sedan. RPM started surging (heavily) at idle. When I put it in gear the surging continues until I gas it. The surging stops but there is very little power. No change in RPM even when accelerator is floored. It will go about 20 mph with a max speed of 35 after about a mile of driving. Took it into Firestone. They were getting various codes ie: P2110, P2127, U2516, U1900, and a lot of others with most saying "No information returned for trouble code" or "DTC description not found". They replaced the PCV and put new plugs in. They couldn't fix it so they didn't charge me a dime, not even a diagnostic fee which I thought was awful nice of them. They suspect the PCM and suggested i take it to the dealership. Took it to the dealership and they got the same codes and also suspect the PCM. Of course they want $2500 to replace the PCM. I paid the $120 for the diagnostic and screamed out of there at 20mph. Looking on the line I see where I can get a programmed PCM (once I send them the VIN) for about $160. It doesn't appear to be very complicated to replace. I know I would have to get the key reprogrammed. Anyone have experience with this or have any other suggestions?

 

Did you ever get this resolved? Im have the same problem

 

Never got it resolved. Everything is pointing to a bad wiring harness. They don't make the harness anymore. Can't find the harness anywhere. I have to get the existing harness refurbished.

 

Dang! Did you end up getting the refurbished PCM you had mentioned?

 

Yes. Did the PCM thing. Very easy install. Just had to call a locksmith to get the key programmed. $50 I think for that service.

 

 

Engine harness. I think it includes the throttle body.

 

I bought a multi meter and started testing a bunch of stuff. Finally after checking maf sensor, fuel pump, alternator, battery, fuses/relays and injectors i decided it must be the pcm finally croked!! I bought my 2004 6s about a year ago, was sceptical at first but took her for a spin on a donut and 3 bald tires shattered windsheild and a hell of a short under the fuse box. But for $900 im very 😊.
my new pcm should be in in about a day!!! If anyone uses F1 for there pcm make sure to call them if you need keys. They charge $100 for 2 keys and they program them for you. Once you have 2 you can program them yourself if you want to use the old keys. Has anyone had to replace a pcm/ecu on there mazda6?

 

Mine still acts up occasionally, and I just unhook the throttle wire clip and hook it back up and it works again.
Def let us know if the pcm is a fix.

 

it wasnt!!! Sucks so now what? Still cant pull codes but i may try again. I read on here to connect to the scaner then turn the key to on. So if not the pcm why is my can not running. I got spark gas air....even a new pcm that was completely pointless. The throttle clip cable? On the top of the block kinda? 4022698732 if anyone has a clue. Wish i could pull a damn code