Terex TA35 Throttle INOP

Code 54 on the TA35 dash is a wheel speed/output speed irregularity flag from the TCU, which pulls the throttle command until the key is cycled precisely because the TCU won't trust an engine command with an unverified output speed input. Per the HeavyEquipmentFix fault-code database, this class of fault (output/wheel speed signal loss or mismatch) is treated as a critical input by the transmission controller and forces a fallback state rather than just logging a code.

Since you've already swapped both speed sensors and the pedal position sensor and static-tested the harness end to end, the fault is almost certainly intermittent rather than a dead component, which static continuity checks won't catch. The most useful analog comes from a mechanic's field report on a related Terex ADT (TA30, same TCU architecture) describing output speed sensor logical-error codes that put the TCU into substitute clutch control or limp mode, and noted the problem is more than likely electrical in nature, with experience specific to the TA35 that Terex ran the wiring harness up high on the right side of the transmission then down next to the exhaust piping, where a rotting exhaust pipe directed hot gases at the harness and burned it up.

Ranked next steps:

1. Wiggle-test and thermal-inspect the harness at that transmission-to-exhaust routing point while the fault is active, since your bench checks were done cold/static and won't show a heat-induced intermittent short or open.
2. Check for a cracked or leaking exhaust pipe near that harness run, per the same field report, as the actual root cause driving harness damage.
3. Inspect connector pins at the output speed sensor and TCU for a loose or backed-out pin rather than a fully open circuit.
4. If all that's clean, pull TCU diagnostic history through Diagnostic Link for the exact SPN/FMI logged at the moment of dropout rather than just the dash code, since that narrows sensor vs. wiring vs. TCU input fault definitively.

Your own thread on Heavy Equipment Forums (posted as "Terex TA35 Throttle INOP") is currently unanswered, so I can't point you to a confirmed fix there yet, only to this harness-routing pattern from a comparable Terex ADT.

Sources:

• 6WG-260 transmission , Terex TA-30 | Heavy Equipment Forums