P1638 code has nothing to do with the performance of your Jaguar or a tune-up. The P1638 is for the instrument cluster problem. Somehow and at some point, the Engine Control Module (ECM) lost communication of the Instrument Cluster (INST), through the Communication Area Network (CAN). We suggest to clear the codes first. If the codes comes back you have to have a Jaguar technician check it for you. The problem could a bad circuit or instrument cluster.