On the 2006 Suzuki Forenza, the P2135 is a fairly straight forward code that is pointing to a fault with the Throttle Position Sensor. The TPS is mounted to the side of the Throttle Body. Carefully inspect the electrical connector and wire harness, looking for any loose, broken or damaged wires. Inspect the Throttle Plate and make sure it moves freely with no binding. Many times this can be excessive build-up on the Throttle Plate. Use some throttle cleaner and a toothbrush to clean the plate and the pivot points of the plate. If the visual inspection checks ok, suspect a faulty TPS. Keep in mind, on SOME versions, the TPS is part of the Throttle Body Assembly and not a stand-alone serviceable item.
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