IBU (SMK + BCM + TPMS) & PCM (ECM/TCM) Control Module (SMARTRA Error)
When turning the ignition switch ON or cranking the engine, the engine ECM begins communication with the IBU (SMK + BCM + TPMS) by sending a VIN (Vehicle Identification Number) request signal to control the engine in a stable manner.
The IBU (SMK + BCM + TPMS) sends an "Ignition Approval Not Possible" signal to the engine ECM when the Immobilizer cannot function. In this case, the engine ECM enters an ignition inhibition state and a driver cannot start the engine (ignition or fuel injection inhibited).
On the other hand, the IBU (SMK + BCM + TPMS) sends an "Ignition Approval" signal to the engine ECM including the VIN and learnt status information when the Immobilizer can function.