TP 31 & TP 32 Differences While the TP 31 and TP 32 modules are physically interchangeable their incorrect usage on the wrong application can result in a hesitation, pinging, or premature coil failure. In extreme cases engine damage can occur. The TP 31, designed to fit Fords first design TFI-IV module applications incorporates an internal current limiter to control coil charge time, (dwell). Operating similar to the current limiter in GM HEI modules, the TP 31 depends on primary current ring-back to determine coil saturation requirements. The effect this has on engine timing is programmed into the ECA to determine the correct total timing curve. The TP 32 also incorporates this circuitry but has the additional ability to have coil charge time remotely controlled by the ECA through the timing advance SPOUT lead. This feature is called Computer Controlled Dwell. The ECA used with this module is programmed with a different timing advance curve to optimize engine performance. Dealers mismatching the ECA and Ignition Module take the chance of creating the previously listed drivability complaints. Testing for a mismatched ECA-Ignition Module combination can be accomplished by performing the Ford Computed Timing test. An incorrect ECA-Ignition Module combination will usually result in a Computed Timing test value outside of the 27-32 degree BTDC window. Always check to make sure that the ground straps are in place and complete connections are made. Visit our Resource Library for available downloads