The CMP should be wired directly to the Ignition Control Module (ICM), and not the ECM. The ICM conditions the signal and sends it to the ECM. The CMP and CKP can both be tested right at the ICM, out front of the engine. If the sensors themselves test good, suspect the electrical connector on the front/lower edge of the ICM base. It is somewhat prone to moisture incursion after 20 years, and could be corroded.