hey all, so I am helping my friend with her 2008 Mazda 6 i with the 2.3.

A couple weeks ago she called me about her car having some hesitation and she said she saw a light flicker but it was to quick to tell what it was. I scanned her codes and found a P0661 code (also a P0126 that she's had for a while) I did some testing on the 2 solenoid valves that sit on the intake plenum chamber and determined the one on the left (passenger side) wasn't working, I replaced it and she said the car felt better for a day or two but then the issue came back. I checked the solenoid and it is still working but this code is still there. I test drove her car and the random hesitation is more evident and the lights that were flickering are the 2 traction lights (TCS off and the swerve light), my first thought was a wheel sensor, however I did a live monitor of all 4 wheel speed sensors and there was nothing unusual when the lights flickered and the hesitation occurred (they were all reading very close to the same and also very close to the speedo). There is also no ABS light coming on. I do get an ABS code C1119 which concerns me and I am not sure if they are related or not. when we got the car back to my house I let it idle in the driveway and the lights flickered a few more times making the idle surge a little in park. I did a few other things that I found on the forums but no improvement (possibly a little of the opposite) inspected and cleaned MAF, turned steering wheel all the way in both directions (to reset TCS), disconnected battery and ECM plugs and then reconnected them all.

To me it seems like something is loose like a connection or a wire shorting out, but I haven't got the first clue as to where I should look on her car. Not even sure where the ABS/TCS module is located. I am an automotive electrician by trade and have been my own mechanic for many years, so I am pretty good with this stuff, just don't know where anything is in this car or how it is all wired/configured.

She did have the transmission replaced (for the second time) I'd say about 4 or 5 months back, no other work done that I can think of.