2007 Chevrolet Trailblazer P0326 Knock Sensor Issue After Engine Replacement
Our 2007 Chevrolet Trailblazer had a completely new engine installed two months ago. Two weeks ago, the check engine light came on and we began hearing a loud, rattling noise from the engine. My husband used an Auto Zone code reader and found fault code P0326 — indicating a knock sensor issue. Unfortunately, he accidentally cleared the code, which led us to return to the original dealer where the engine was installed. At that time, the rattling noise had stopped, and no issues were detected during inspection by Victory Chevy. However, while driving home, the check engine light came back on along with a distinct rattling sound. This caused significant frustration. We then took the vehicle to a local mechanic who replaced both knock sensors. After driving it for about 25 miles, the P0306 code returned and the noise persisted. The mechanic subsequently ordered and installed an AC Delco knock sensor on Bank 1. Despite this, the same P0326 code reappeared, and the rattling noise continues intermittently. We are now seeking advice — has anyone experienced a similar issue after engine replacement? Is it possible that the new engine itself is faulty or improperly installed? Sincerely, Insanechevy
The rattling noise is the actual problem — not necessarily a sensor failure. The knock sensor detects vibrations and responds to knocks; if there's physical engine noise, it will trigger the P0326 code. New engines should not produce knocking sounds under normal conditions. If the issue reappeared after installation, it strongly suggests a problem with the engine or its mounting components. You should contact the shop that performed the engine replacement — they are responsible for ensuring proper installation and function. The vehicle was inspected at their facility and no issues were found at the time. Since symptoms returned, this indicates a potential defect or improper workmanship. It's essential to document all repair visits with order numbers and keep records of any warranty claims. There should be some form of warranty on a new engine — simply put, 'cover your bases' and ensure accountability.