DMax Diesel: Boost Issues & Power Loss with Hissing

Had a similar issue with a 2021 Silverado diesel. The symptoms you're describing match what I experienced, turbo lag, power loss, and that characteristic whistling noise. The problem turned out to be a faulty wastegate valve, which was causing inconsistent boost pressure. The check engine light came on because the pressure sensor was detecting irregular readings. After a complete diagnosis, the workshop found the wastegate wasn't operating properly, leading to boost control issues. Got it fixed for around 860 Euro, including parts and labor. The repair made a huge difference, power came back immediately, and the engine ran smooth again. Before jumping to conclusions though, what's your exact engine size and how many miles are on it? Also, have you scanned for specific error codes? These details would help narrow down if you're dealing with the same issue. Quick tip: While waiting for repairs, watch your boost gauge (if equipped) during acceleration, any erratic movement could confirm the wastegate theory. Also check your intercooler connections, as these can sometimes cause similar symptoms. Would need more info about: Specific error codes, Current mileage, Any recent maintenance history, Whether symptoms are worse during cold or hot weather

Thanks for sharing that experience. My DMax has 135038 KM and was just serviced last month. Got the codes scanned yesterday, P0299 and P0234 showing up, which points to boost control problems. The MAP sensor readings are all over the place according to the scan tool. Seeing boost pressure dropping to almost nothing under load, then spiking erratically. The whistling gets louder when this happens. Checked the intercooler thoroughly for any obvious cracks or loose connections but everything looks solid there. The throttle body and surrounding hoses appear intact too. What's concerning is how quickly it's gotten worse over the past week. Definitely going to get the wastegate checked based on your experience. Did you notice any blue smoke before your repair?

Just wanted to follow up on your latest update. Since my Silverado repair, I've learned quite a bit about these boost pressure issues. Those P0299/P0234 codes you're getting are exactly what I saw, classic signs of wastegate problems. The erratic MAP sensor readings you described match my situation perfectly. The quick deterioration you're experiencing is really similar, mine went from minor boost issues to serious power loss in about 8-9 days. Interestingly, I didn't see any blue smoke either before the wastegate repair, so that's actually a good sign that points away from internal turbo damage. One thing I noticed when checking my throttle body before the repair, there was some carbon buildup affecting the airflow. Might be worth checking that while you're troubleshooting. The irregular boost pressure readings you're seeing through the MAP sensor are almost identical to what my mechanic showed me on the diagnostic readout. Quick tip from my experience, if you're planning to drive it before getting it fixed, try to keep the RPMs moderate. My mechanic explained that excessive boost pressure spikes can potentially cause more damage if the wastegate is malfunctioning.

Thanks for that detailed follow-up. Really helpful to hear your experience was so similar. Just booked it in for next week to get checked out, not taking any chances with these symptoms getting worse. Makes sense about keeping the RPMs down. Been babying it since the problems started and definitely noticed it runs a bit better when I'm gentle on the throttle body. The turbocharger seems less stressed that way. Good to know about the carbon buildup too. I'll mention that to the workshop when they check the boost pressure system. The fact that you didn't have blue smoke before your repair is reassuring, was worried about more serious turbo damage. Quick question, did your check engine light stay on constantly or did it flicker? Mine's steady, and the MAP sensor readings are still bouncing around like crazy. The boost pressure drops are most noticeable when trying to accelerate uphill or merge onto highways. Will update once I get the diagnosis back from the workshop. Starting to feel pretty confident it's the wastegate based on all these matching symptoms.