Colloids form transient colloidal crystals that autonomously disassemble and reassemble in response to electrochemically generated pH transients. We utilize a time-invariant multimode electric stimulus to drive competing electrokinetic flows between colloids and an electrochemical reaction cycle that generates pH transients that modulate the flow magnitudes in time. As a result, colloidal crystals autonomously alternate between transient assembly and disassembly states with voltage tunable lifetimes ranging from a few seconds to nearly 1000 seconds (Figure ). The rapid reconfiguration times contrast prior chemically fueled systems that have lifetimes typically ranging from hours to days. The electrochemical reaction network modifies the local solution pH and does not alter colloid surface chemistry, which mitigates irreversible aggregation seen in conventional fuel driven approaches. In contrast to prior work showing pH spikes of > 50% required to modify colloid protonation state, transient behavior was observed here for pH increases of ~10%. We expect this mechanism can be broadly applied to tune transient behavior of other types of active colloids, such as colloidal motors or functional colloidal gels. Likewise, we expect this approach can be extended to other soft materials and molecules that respond to pH changes, such as polymer hydrogels and small molecule hydrogelators.