U0101: How to Diagnose & Fix — Lost Communication with TCM

The ignition switch and SKREEM (Sentry Key Remote Entry Module) fail, preventing the vehicle from starting or causing intermittent no-start conditions. The SKREEM module reads the transponder in the key and communicates with the PCM. Failure causes 'no bus' communication errors.

The Quadra-Trac transfer case encoder motor on Grand Wagoneer models fails to properly shift between 2WD, 4WD Auto, 4WD Low, and Neutral modes, leaving the vehicle stuck in a single drive mode or displaying a 'Service 4WD System' message. The BorgWarner transfer case encoder motor and position sensor can develop electrical faults or mechanical binding, particularly after exposure to water or road salt. Owners report being unable to disengage 4WD Low or experiencing grinding/clunking when attempting mode changes.

Separate from the clutch-pack shudder already documented: the DPS6 PowerShift's Transmission Control Module, mounted on the transmission and exposed to heat, fails electrically. The car suddenly loses drive while moving, will not start, drops into limp mode, or the cluster throws a transmission fault with stored U0101 (Lost Communication with TCM). Ford acknowledged it with Customer Satisfaction Program 14M02, extending TCM coverage on 2011-2015 Fiestas to 10 years / 150,000 miles. Because a failed TCM cannot be reflashed, replacements also require a Ford reprogram, and parts shortages in 2019-2021 left owners waiting weeks.

The Transmission Control Module (TCM) for the Allison 1000 transmission is a separate module mounted outside the transmission (on 2007-2012 trucks it sits in the engine compartment near the underhood fuse block), and it can fail or lose communication. On 2007-2012 trucks, GM links loss of TCM communication (DTC P0880/U0101) to electrostatic discharge from aftermarket serpentine belts. When it fails, the transmission goes into limp mode or refuses to shift from 3rd gear.

The Totally Integrated Power Module (TIPM-7 generation) is the Challenger's central fuse-and-relay box and power-distribution computer, mounted in the engine bay. It manages nearly every electrical circuit, and a single failed solder joint, blown internal circuit-board trace, or — most commonly — a degraded internally-soldered fuel-pump relay can cripple the whole car. Because the fuel-pump (ASD) relay is hard-soldered into the TIPM circuit board (not a serviceable plug-in relay), owners cannot simply swap a relay. The dominant root cause is contamination/degradation of the sealed relay contacts (silicone vapor that hardens into insulation and burns under load) compounded by water/moisture intrusion and corrosion of the board, which is why failures are intermittent and often produce no stored trouble codes. The result is a cluster of seemingly unrelated, hard-to-diagnose faults: a relay stuck OFF causes random no-start, no fuel-pump prime, and mid-drive stalling; a relay stuck ON causes the fuel pump to run continuously and drain the battery overnight. This is the root cause behind the model's worst CarComplaints electrical category — the 2013 Challenger alone has a dedicated "bad TIPM" complaint cluster, with failures averaging around 43,000 miles (reported range roughly 8,000–76,000 miles), well within the life of the car. Critically for Challenger owners, the fuel-pump-relay recall campaigns (NHTSA 15V-115 / Safety Recall R09 and the 2019 redo 19V-813) covered the Durango and Jeep Grand Cherokee — NOT the Challenger. NHTSA's recall list for the Challenger shows only airbag and alternator campaigns, no TIPM recall, so Challenger owners pay out of pocket (commonly ~$700–$1,100). The 2008–2014 (LC-body) cars share the TIPM-7 implicated across the Chrysler/Dodge/Jeep lineup; 2010–2014 see the heaviest complaint volume.