P0888: commanded relay power is missing at the Jeep TCM

P0888 is the transmission relay-output-always-off fault in the 2002 WJ/WG 45RFE/545RFE manual. The TCM is commanding the relay on but sees less than three volts on the monitored relay-output circuits. The disagreement between command and feedback is the defining evidence.

The relay is only one part of the path

The diagnostic possibilities include a missing fused battery feed, an open output circuit, an open relay-control circuit, an open relay ground and shorts to ground. A relay stuck open is also listed. Consequently, a replacement relay cannot be expected to repair every P0888.

The factory tree checks the external supply, command, ground and output paths before reaching a controller replacement decision. A technician's isolated circuit tests establish whether power can reach the TCM through the output wiring independently of normal relay operation. That observation helps distinguish damaged wiring from failed relay switching; it is not an owner-level instruction to bridge the relay.

The starts-since-set counter helps choose between active and intermittent diagnosis, but the manual cautions that this counter applies only to the last code set. Reading it as the age of every stored code can create a misleading timeline.

Repair confirmation

Verification should show that the relay output now follows the controller command and that related transmission faults do not recur during the specified checks. Preserve the original fault set because missing common power can affect other monitored circuits. This interpretation and its voltage boundary apply to the cited Jeep manual's five-speed diagnostic branch, not every vehicle using P0888.

Source: DaimlerChrysler 2002 WJ/WG transmission diagnostics, physical PDF pages 144–147. The original PDF is also available as WG/02wget.pdf in the factory-manual archive.