Boost stuck at -9.70 to -9.77 at idle and...

...barely getting boost. This randomly happen while going aggressive merging on a highway.

ENGINE/DRIVABILITY

Year/Make/Model: 2012 Mazdaspeed 3
Mileage: just over 140k
Location: New York City
Concern: see links: https://www.revisionsrus.com/logs/2484 \ https://www.revisionsrus.com/logs/2485 \ https://www.revisionsrus.com/logs/2486
DTC's: P0172 on and off or hidings in the background. P0335 on and off; and randomly getting the fan malfunction code where in traffic, coolant temp will get up to 240. U0140 I had for years. Nothing really tells you what needs to be done to have that code permanently disappear.
Modifications: in my signature
ECU/Tuning Software: Cobb Accessport V3
Tuner: Hypnotic
Is the concern intermittent? Somewhat
Can you duplicate the concern? I have the logs above.
Recent Repairs: injector seals...fuel leak (P0172 was before that)
Correction: visual check to see if any vacuum lines were broken or couplers loosen,cleaned MAF sensor, soapy water test everywhere. I was planning to replace the O2 but I wanted to troubleshoot more to get the P0172 out the way. the fan malfunction...might need to change with module? The P0335 I change the crankshaft position sensor but code goes off and on.

 

Couple things.

Check the wiring itself for the crank sensor to the ECU. Make sure there isn't any damage on the harness anywhere.

Take a log of the fuel trims now, then change your oil. If the trims go leaner then before, you could have a leaking HPFP into the crankcase causing the oil to thin.

Replace the thermostat with a good OE unit. Not aftermarket. Some aftermarket ones are listed for the speed but won't work right as they don't open fully. Get a genuine Mazda one.

I could help more with the U0140 code if you can get the descriptor for what device has lost communication.

 

Thank you for replying. It's been a busy week and this is the first opportunity I've had to get on a computer. Communication Error to Body Control Module is the U0140 code.

idle log? I am asking because I thought the links shared that information. About the oil, it was changed 2 weeks ago. It is needed again because of the mix? I have no issues changing it again. I am curious to know what you are looking for besides a leak.

Curious...what makes the thermostat the possible solution?

I will try to look into this soon. The code is intermittent. For example, the last few days...no code.