My ST170's engine management light is permanently on, fault code is P1518, Intake Manifold Runner Control stuck open. According to other forums, this is a fairly common failure usully caused by the plastic control cam on the manifold or fixing pin breaking, leaving the control cable from the IMRC module unattached. So I checked the control cam on the inlet manifold, cable is still attached, and the IMRC module pulls the cable as it should when the engine is switched on. I can only assume the IMRC module is incorrectly reporting the fault, but every time I get the fault code re-set, it reappears soon after. I'm trying to avoid forking out the £200 to replace a unit which appears to be working fine, so does anybody have any ideas what the problem might be or how to get the light to stay off?