Unstable Idle - P0101 and then P0113, dealership wants to replace the PCM

jetstreamblue

Member
:
2012 Mazda5 GS
My 2012 Mazda5 with about 95,000 km just developed an unstable idle on the weekend. Revs would go up and down continuously when stopped. Moving and the the car drives mostly fine. Just started in the middle of a drive after getting off the highway. Finally threw a code P0101 (MAF sensor problem), so I went ahead and cleaned the MAF. That didn't work, so I threw in a new OEM MAF sensor. When that didn't work as well, I left it with the dealership, who came back and says that I need a new PCM! I decided to sleep on it, and today pulled the codes again and found a P0113 (IAT sensor high). The MAP and IAT are in the same module, so that's already a brand new sensor.
What does everyone think? The new PCM needed? Or any other ideas?
 
The air filter isn't dirty / clogged, is it?

Just changed it today in case it was that. Old filter didn't seem too dirty. Anyway, no immediate change to the unstable idle.

Does the PCM need time to "re-learn" after a MAF sensor is replaced? The idle does seem to be better after I put in the new sensor, just not back to where it should be.
 
This is where I would be checking live data on a scan tool, doing electrical testing, making sure PCM is providing good power and ground to the sensors, printing off the wiring diagrams and mapping it all out. If you don't know how to do any of that then just trust the dealer has already done the diagnosis. Make it clear you aren't paying for the new pcm if it doesn't fix it as you are relying on their expertise.


Sent from my iPhone using Tapatalk
 
Thanks for all the inputs.
I just realized the PCM is supposed to be covered by the extended emissions warranty that's still valid. Getting the service adviser to confirm now.
I just hate having to check warranty coverage myself when the dealership should be responsible for this. Not the first time I've had to do this.
 
Another update....

Dealership confirmed the PCM will be covered under the emissions warranty. But the part is on backorder and won't be here for several weeks! Argh!
In the meantime, I'm trying to get them to refund the diagnostic fee I paid, as normally you shouldn't be charged diagnostic fee for a warranty issue.
 
That's a bummer that it was on you to discover it was covered under warranty. I'd be upset too. Since I've never bought even a remotely new car before, I've never had the pleasure. Good to know!


Sent from my iPhone using Tapatalk
 
Last edited:
Back