Problem: Depressing the accelerator, even all the way down, often results in the car refusing to downshift in response. Result is very sluggish acceleration in the higher gear it was in when I depressed the pedal.

Vehicle: 2016.CX-5 GT AWD, automatic transmission, ~97Kmi.

My question is: Which specific areas (system, maintenance, whatever) would you recommend to check?

Such as:

• Sensors at the accelerator pedal
• Sensors in the engine bay
• Throttle position equipment
• Connection from the accelerator pedal to the engine bay (whatever's involved with this ... cabling, hydraulics, whatever)
• Throttle body itself
• MAF sensor
• Vacuum leak(s)
• Cables or hydraulics involved in the transmission's gear changes
• Other?

Uncertain what to begin checking, what's most likely to be causing this frequent refusal of the car to downshift into a proper gear.

The vehicle is a 2016.5, GT model, automatic transmission, ~97Kmi. Haven't yet cleaned the throttle body or MAF, since purchase (@ 79Kmi). Am not noticing any other issues with the transmission. Shifts fine in the +/- (tiptronic) manual shifting mode. Usually downshifts fine, in automatic mode. About 15Kmi ago, I had the transmission and diff fluids properly swapped by a good transmission shop. No strange noises. Gears all seem nice and smooth, shifting properly most of the time. The car's performing very well, other than this issue.

Open to any suggestions on which parts/systems to look at, what maintenance to get done, which items to check first.

 

One obvious question, when did the issue begin relative to the fluid change? Exactly what fluid was used? How much was added? There are many potential causes, but these are the first ones I would check.

 

The issue is unrelated to fluid change, I believe. The transm/diff fluids were changed more than 15Kmi ago by a competent shop, and it was all the correct Mazda-spec stuff (which I insisted on). And this occasional refusal to downshift with heavy throttle was occurring prior to this; and it isn't any worse since.

I don't know whether it's a glitch in the fuel+shifting maps in the vehicle, or something mechanical (ie, TB/MAF cleaning), or something else. The incidence of this issue is random and occasional, but frequent enough to be a pain.

 

Book it in with Mazda to check for fault codes, plus a transmission relearn.

 

Same behaviour in sportsmode ?

 

Yes, both normal and "Sport" automatic modes exhibit the issue occasionally.

 

Unfamiliar with what a "transmission re-learn" is. Do they essentially reset the transmission portion of the ECU in order to force the system to re-map its understanding of typical driving behavior, etc.?

Any idea what such a thing might reasonably cost? (Can't imagine it's much time, if just a couple minutes to flip a reset on the box, though I suspect they'd want to charge a small fortune to do it.)

 

Try this.
How do you reset a Mazda transmission control module?
To reset your transmission turn on the ignition, not the motor. Press the gas to the floor for 30 seconds then release and turn on your vehicle.

-------------------------------------------------------------------------------------------
Second if first attempt didn't work:
Resetting your PCM will only take a few minutes.

1. Open your Mazda's hood.
2. Disconnect the "Negative" terminal clamp to your Mazda's battery. ...
3. Sit in the driver's seat of your Mazda.
4. Push down and release the brake pedal five times consecutively.
5. Reconnect the "Negative" terminal clam on your Mazda's battery.

 

Out of caution (as I've not seen these procedures previously) ...

1. Are these Mazda specific, Mazda recommended procedures to do these resets, or generic ones that also apply to Mazdas in general? (Just wondering, as I haven't seen them referenced anywhere.)

2. Is that "press pedal five times" thing a programmatic sequence requirement, or really just to ensure the capacitors are zapped of any stored charge?

3. Poking around on the internet, I've found a couple of variations of the above sequence. Some suggest it's for the capacitors. Some have a more-elaborate multi-step process after the battery cable's disconnected (lights, horn, brake pedal). None indicate it's a required sequence the ECU/PCM is looking for, programmatically, to accomplish a specific reset (versus another reset via use of a different sequence).

4. BTW, it's also time to take apart the throttle body and do a cleaning on the thing. I would imagine that if the acceleration/throttle maps are going to be re-learned, now's the time to get the TB/MAF cleaned so that when it re-learns it'll learn the correct, cleaned, zippy handling of throttle (instead of the likely somewhat-gunked-up TB it has now). If doing this "re-learn" would it make sense to first clean the TB/MAP prior to attempting?

 

TCM gets confused sometimes, just disconnect negative terminal for a few minutes, pressing brake 5 times to discharge capacitors IMHO is BS.