Surprisingly, low voltage can cause P158B. The throttle motor requires a stable 12V–14V supply. If your battery is dying or your alternator is weak, the throttle body may not receive enough power to move correctly, causing an adaptation fault.
But Alex’s favorite answer came from a retired mechanic named Jean-Pierre who ran a blog called Renaults and Regrets . p158b renault
It is also reported, less frequently, on the naturally aspirated 1.6 16V engines (K4M). Surprisingly, low voltage can cause P158B
The P158B code indicates that the Engine Control Module (ECM) has detected that the (or the idle speed control valve) is operating outside of its factory-specified parameters. Because the idle control system manages the engine's RPM when the vehicle is stationary or moving at very low speeds, a malfunction here often leads to immediate drivability issues. Common Symptoms But Alex’s favorite answer came from a retired
In simpler terms: Your car’s brain asked the throttle to move, but the throttle didn't respond correctly.
The throttle body needs to "learn" its zero position (hard stop) and full-open position. Many generic scanners cannot do this. You can try the manual pedal method (varies by model, typically: turn ignition on, wait 15 seconds, press pedal slowly to floor, release slowly, turn off ignition) but professional diagnostic software is better.
A mechanical or electrical failure within the internal motor of the idle-speed control valve itself.