P158b Renault <2027>

In some high-mileage Renaults, the turbocharger bearings wear out, causing shaft play. This leads to inconsistent boost pressure. However, P158B from purely mechanical turbo failure is less common than VGT carbon buildup.

Replace any cracked or hardened vacuum hoses. Use 3.5mm or 4mm silicone vacuum hose for longevity. Ensure the vacuum reservoir (a small black plastic ball) holds pressure. If not, replace it. p158b renault

Measure the resistance of the vacuum solenoid valve. Typical values are 20-40 ohms. If open or shorted, replace it. Also, apply 12V to the solenoid and confirm it clicks and allows vacuum to pass. Replace any cracked or hardened vacuum hoses

Carbon buildup on the variable geometry vanes of the turbocharger prevents smooth movement. Over time (especially with city driving or poor-quality fuel), the vanes seize in one position. When the ECU asks for more boost, the vanes cannot adjust, leading to underboost or overboost, which triggers P158B. If not, replace it