There are few things more frustrating than a time-consuming comeback caused by a ‘parts-darts’ approach to diagnostics. Robert Shervill of RMS Diagnostics investigates a persistent electrical fault on a Peugeot 207 that had already seen a costly ECU replacement fail to resolve the issue.
By moving beyond visual inspections, Shervill identifies a deceptive fault within a standard blade fuse that appeared perfectly intact to the naked eye.
The investigation focuses on a variable valve timing (VVT) control solenoid that had lost power, where initial testing revealed a 3.5V signal.
Robert explains that this was likely a back-feed from the ECU. By tracing the circuit back to the engine bay, he demonstrates that while the fuse looked identical to a brand-new component, a multimeter check under load confirmed the voltage drop was occurring within the fuse itself.
By cutting away the plastic casing to reveal the root cause, Robert found that the metal leg had completely corroded at the point it entered the plastic housing.
This hidden rot created an open circuit impossible to detect visually.
