P0884: a Jeep transmission controller restarted while moving

The 2002 WJ/WG 45RFE/545RFE manual describes P0884 as power-up at speed. The TCM has just initialized, yet it sees a valid forward selector position and output speed above 800 rpm. That combination is inconsistent with an ordinary stationary startup and records evidence of a power interruption or restart.

Why an intermittent supply can escape a quick test

The generic title, intermittent TCM power input, is useful here, but the factory logic adds the timing. A supply that is normal after the vehicle stops may still have interrupted the controller while moving. Measuring battery voltage once in the workshop therefore does not recreate the evidence that set this code.

The specified investigation examines three routes: fused battery power, fused ignition-switch output and the TCM grounds. An intermittent open or a short to ground in any of the relevant paths is a reason to examine harnesses and connections. The diagnostic chart does not identify a particular relay or declare the TCM defective merely because P0884 was stored.

Selector validity also matters. The manual's preliminary procedure includes the shift-lever-position test and directs a failed result to its own shifter diagnosis. This prevents an unreliable range input from being treated as trustworthy background information.

Verification without provoking the event

A workshop should document the supply or connection fault found and complete the prescribed transmission verification. Do not switch the ignition off while driving to reproduce the code. The speed and initialization criteria above are specific to this Jeep manual; other transmissions can implement P0884 differently.

Source: DaimlerChrysler 2002 WJ/WG transmission diagnostics, physical PDF pages 143–143. The original PDF is also available as WG/02wget.pdf in the factory-manual archive.