DTC codes / P08xx · Transmission / P0888
P0888 indicates that the transmission control module (TCM) has detected a fault in the power relay sense circuit, which is the feedback line that confirms the relay is supplying voltage to the TCM. The TCM expects a specific voltage on this circuit when the relay is commanded on, and it sets this code when the signal is missing, erratic, or out of range.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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