P0325 code keeps coming back. Any ideas ?

[4g63gst20]

Hi guys so I have a 2012 Chevy sonic turbo with 88k miles. Stock tune for the past year and about 4 months ago I started having issues with it. First an underboost code and now a knock sensor code that keeps coming back. Dealership replaced the knock sensor itself and upstream oxygen sensor with no success. The code comes and goes and I do feel like the car looses power around 2k rpm then after 3k it takes off normal. I have a boost gauge and I'm seeing 10psi sometimes very rarely max 10 psi. Any ideas guys before I dump this car in a lake ?

 

[Maddmatts]

It's possible the new sensor wasn't plugged in fully and it backed out and now making an intermittent connection. There could be a bad ground somewhere too.

You can check the wiring by unplugging the sensor and turn the key to run (don't start the engine) and make sure it shows some amount of voltage. Sensors are usually run at 5v.

 

[mja]

I'd think wiring or ECM related too, but rhe underboost is odd. How long did that happen before the knock sensor code?

My order of attack for knock sensor would be, try a 2nd new sensor - 15$. Check voltage at the female leads of harness, check resistance through entire wires for continuinity (track colors back to ECM & unplug from there). Have ECM reflashed, maybe a reset will help - unplug battery a few hours and reconnect. Check spark plugs for fouling & replace if its been a while (>1 or 2 yrs). Decrease engine vibrations - if aftermarket motor mounts or exhaust, swap em back to stock if still having issues.

I've had wires cut inside the stock Sonic engine harness, engine bay runs hot. Splicing the harness doesn't work well with these newer ECMs.

 

[4g63gst20]

I got the car back from the dealership and they said they connector was the culprit this time. They don't know what happened to it but they were getting high resistance when testing it.
Also found an injector leaking and a cam actuator solenoid.

Hopefully this time is fixed . I've been having this issue for a while

 

[mja]

The engine bay just gets really hot, high temp thermostat + turbo, can't be good for copper wiring. A connector broke its wire inside the connector on mine, took forever to track down since the wires themselves were good, I understand the frustration.

Hope it's running well, did they get you a new wiring harness?

 

[4g63gst20]

Supposedly they got me a new harness.1 full day and the code didn't come back. One more thing I noticed is that when I ran a boost leak test I lost some pressure from the pcv valve hose going to the turbo and intakr manifold. I tried to get them to replace that too but that line is never pressurised since that's just a return line. Anybody know what size hose I should buy to replace the hard plastic one ? I'd hate to pay $70 for a new one

 

[mja]

See post #120 here
http://www.sonicownersforum.com/for...-oil-catch-can-accessing-your-tophats-12.html

& #48 here
http://www.sonicownersforum.com/for...ne-discussion/10825-1-4t-pcv-explained-5.html

 

[4g63gst20]

Thanks for the info, I'm getting close to the end of my chevy warranty and will replace the pcv pipe soon.