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U01212021 Model Year TelemetryHigh Severity

U0121 on 2021 Chrysler Pacifica Hybrid

Lost Communication With Anti-Lock Brake System (ABS) Control Module

Technical troubleshooting wire for fault code U0121 specifically tailored for the 2021 Chrysler Pacifica Hybrid. Includes wiring sensor pinouts, freeze frame PID parameters, and step-by-step diagnostic tree.

2021 Engine Control Module (ECM) Specific Calibration
Chrysler Pacifica Hybrid2021 Pacifica Hybrid
2021 Chrysler Pacifica Hybrid
Van • 3.6L Atkinson-Cycle V6 + Dual Electric Motors (260 HP PHEV / 32-Mile EV)
2021 Stats
Vehicle
2021 Pacifica Hybrid
3.6L Atkinson-Cycle V6 + Dual Electric Motors (260 HP PHEV / 32-Mile EV)
ECU Subsystem
Automotive OBD-II
SAE Mode $01 & $02
Est. Repair Cost
$200 - $700 (DIY: $40 - $180)
OEM Parts & DIY
Urgency Level
High
Drivable (Short)
Switch Pacifica Hybrid Model Year for U0121
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Common 2021 Pacifica Hybrid Symptoms

  • System alert or indicator light illuminated (U0121)
  • Intermittent performance throttling or unexpected operation halts
  • Audible sensor relay clicking or anomalous status telemetry in dashboard logs
  • Degraded operational throughput or error dialog popups on startup
  • Readiness monitors failing state emissions or system compliance audits

Likely Root Causes on 2021 Pacifica Hybrid

  • Component aging, oxidation, or degraded internal circuit element (ABS Fuse / Module Connector)
  • Wiring harness abrasion, loose terminal pin, or ground voltage float
  • Outdated firmware microcode or incompatible software driver update
  • Thermal stress or excessive operational duty-cycle fatigue
  • Contamination from carbon buildup, moisture ingress, or dirty filtration

Step-by-Step Fix Protocol for 2021 Chrysler Pacifica Hybrid

Step 1: Scan & Record Freeze Frame Data

Connect an OBD-II scanner to the DLC port under the driver dashboard. Record engine RPM, Short Term / Long Term Fuel Trim (STFT/LTFT), and engine coolant temperature at the moment U0121 set.

Step 2: Inspect Wiring Harness & Pin Voltages

Inspect the sensor connector on the 2021 Pacifica Hybrid engine bay. Use a multimeter to verify reference voltage (5.0V / 12.0V) and ground continuity.

Step 3: Component Replacement & PCM Reset

Replace the verified defective component using OEM or equivalent grade parts. Clear DTC U0121 and complete an EPA drive cycle to verify readiness monitors set to READY.

Recommended Parts & Testing Tools

Equipment for Diagnosing 2021 Chrysler Pacifica Hybrid (U0121)

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2021 Chrysler Pacifica Hybrid OEM Replacement Sensor

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Direct-fit replacement assembly engineered to OEM tolerances for 2021 Chrysler Pacifica Hybrid.

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Sensor Signal Voltage Meter

AstroAI Auto-Ranging Digital Multimeter

4.6 / 5.0 (Best Seller)

Essential for testing 0.1V–5.0V sensor reference signals, ground continuity (<0.20Ω), and harness resistance.

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BlueDriver Bluetooth Pro OBDII Scan Tool

4.7 / 5.0 (50,000+ Reviews)

Reads and clears enhanced codes (ABS, Airbag, Transmission, Engine) & live freeze-frame telemetry on phone.

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Full Reliability Report2021 Pacifica Hybrid ProblemsSafety Recalls2021 Pacifica Hybrid RecallsAll Generation YearsPacifica Hybrid U0121 Master Hub