U0123 – Lost Communication With Yaw Rate Sensor Module

System: Network | Standard: ISO/SAE Controlled | Fault type: General

Definition source: SAE J2012/J2012DA (industry standard)

DTC U0123 indicates that one or more control modules have detected a loss of communication with the yaw rate sensor module over the vehicle network. The yaw rate sensor module is typically used by stability-related systems to understand rotational movement of the vehicle body, so the communication link is treated as important. How U0123 is detected, how quickly it sets, and whether it is stored as current or history can vary by vehicle and by operating conditions. Always confirm module locations, network type, connector views, and pinpoint tests using the appropriate service information before replacing parts or making wiring changes.

What Does U0123 Mean?

U0123 – Lost Communication With Yaw Rate Sensor Module means the vehicle’s networked controllers are not receiving expected messages from the yaw rate sensor module. This is a network communication fault, not a direct indication that the vehicle is physically yawing incorrectly. In practice, the code sets when communication is interrupted, missing, or considered invalid for long enough to fail the network monitor. SAE J2012 defines how DTCs are structured and categorized, and U-codes are used for network-related faults; however, the diagnostic path still depends on the specific network architecture and module strategy used on a given platform.

Quick Reference

• Subsystem: Vehicle network communication to the yaw rate sensor module.
• Common triggers: Module not powered up, network open/short, poor connector contact, or a module that stops transmitting.
• Likely root-cause buckets: Wiring/connector faults, power/ground issues to the yaw rate sensor module, network line faults, module internal failure, configuration/software issues (varies by vehicle).
• Severity: Often affects stability/traction-related functions; vehicle may drive but with reduced assistance and warning indicators.
• First checks: Scan for related U-codes, verify yaw rate module power/ground, inspect connectors for fit/corrosion, and confirm network integrity.
• Common mistakes: Replacing the yaw rate sensor/module without verifying power/ground and network continuity or ignoring other network DTCs that point to the true fault area.

Theory of Operation

The yaw rate sensor module (whether a standalone module or integrated into a larger assembly, depending on vehicle design) transmits yaw-related data over the vehicle communication network at regular intervals. Other controllers use these messages to support stability-related calculations and plausibility checks with additional inputs. For the network to be considered healthy, the module must be powered and grounded correctly, the network lines must maintain integrity, and the messages must be present often enough to satisfy the receiving module’s monitoring logic.

U0123 sets when the receiving controller(s) detect missing communication from the yaw rate sensor module beyond an internal timeout or when network conditions prevent reliable message exchange. Because the monitor is communication-focused, root causes commonly include loss of module power/ground, damaged wiring, poor terminal contact, network shorts/opens, or a module that is offline and not transmitting.

Symptoms

• Warning lamps: Stability/traction/brake-related indicators illuminated or messages displayed.
• Reduced assistance: Stability/traction control functions may be limited or disabled.
• Handling feel: Changes in intervention behavior during low-traction events (system may not intervene as expected).
• Multiple DTCs: Additional network communication codes stored in one or more modules.
• Intermittent operation: Symptoms may come and go with vibration, temperature changes, or after cycling the ignition.
• Scan tool access: The yaw rate sensor module may not respond to diagnostic requests or may appear offline.

Common Causes

• Open circuit, short-to-power, or short-to-ground in the communication network wiring between modules (varies by vehicle)
• Poor connector seating, terminal spread, corrosion, or moisture intrusion at the yaw rate sensor module connector or at a related junction/inline connector
• Loss of power feed to the yaw rate sensor module (blown fuse, failed relay, open in the power supply circuit)
• Loss of ground to the yaw rate sensor module (open ground, high resistance, loose ground point)
• High resistance in the network circuit due to damaged wiring, pin fit issues, or improper repairs
• Yaw rate sensor module internal fault that prevents network communication
• Another module on the network malfunctioning and disrupting bus communication (network “down” condition)
• Incorrect module configuration or software-related issue after service (varies by vehicle and procedures used)

Diagnosis Steps

Tools typically needed include a capable scan tool that can read network DTCs and module status, a digital multimeter, and back-probing leads appropriate for the connectors. Access to vehicle-specific service information is important for connector pinouts, fuse/ground locations, and network topology (which modules share which bus). If available, a breakout box or approved terminal test kit can reduce connector damage during testing.

1. Confirm the complaint and code context: Scan all modules for DTCs, not just one. Record U0123 and any other network, power supply, or stability-related codes. Save freeze-frame or event data where provided.
2. Check module presence on the scan tool: Attempt to communicate directly with the yaw rate sensor module using the scan tool. Note whether it is “offline/not responding” or intermittently available, as this guides whether to focus on power/ground versus network integrity.
3. Assess overall network health: If multiple modules are offline or many communication codes are present, treat this as a possible network-wide issue. If only U0123 is present, focus on the yaw rate sensor module circuits and its local harness routing.
4. Verify power supply and ground basics first: Using service information, identify the module’s power feeds and grounds. Check relevant fuses and any related relays under load (not just visually). If access allows, perform voltage-drop testing on the module ground path while the circuit is powered to find high resistance.
5. Inspect connectors and harness routing: With ignition off, inspect the yaw rate sensor module connector(s) and nearby harness for water intrusion, bent pins, pushed-out terminals, poor pin fit, chafing, or prior repair work. Reseat connectors and ensure locking tabs fully engage.
6. Perform a controlled wiggle test: While monitoring scan tool communication status (and, if available, network DTC counters), gently wiggle the harness and connector near the yaw rate sensor module and along known pinch points. If communication drops in/out, isolate the exact location by moving in smaller sections.
7. Check for opens/shorts in the network circuits: With the system powered down per service information procedures, test continuity end-to-end for the communication lines between the yaw rate sensor module connector and the next accessible connector/junction. Check for short-to-ground and short-to-power on each line. Avoid damaging terminals by using the correct probing method.
8. Evaluate for high resistance and poor terminal contact: If continuity “passes” but the fault persists, look for intermittent/high resistance issues: lightly load the circuit if procedures allow, inspect terminal tension, and repeat checks while flexing the harness. High resistance can cause communication loss without a full open circuit.
9. Differentiate module power/ground fault from module internal fault: If the yaw rate sensor module has correct power and ground (verified under load/with voltage-drop checks) and the network circuits test good to the nearest junction, yet the module remains non-communicative, suspect the module itself or configuration/software state (varies by vehicle).
10. Use live-data logging where applicable: If the module communicates intermittently, log communication status and related stability/vehicle dynamics parameters during a short test in a safe area. The goal is to capture when the module drops off the network and correlate it to vibration, movement, or electrical load changes.
11. Clear codes and validate the repair: After repairs, clear all DTCs and perform a verification drive or functional check per service information. Re-scan all modules to confirm U0123 does not return and that no new network codes were introduced.

Professional tip: When diagnosing a lost communication DTC, prove power, ground, and network integrity at the yaw rate sensor module connector before condemning the module. Many repeat failures come from “good-looking” connectors with poor terminal tension or hidden corrosion; voltage-drop testing and a careful wiggle test while monitoring module online status are often more revealing than static resistance checks alone.

Possible Fixes & Repair Costs

Repair cost and effort for U0123 can vary widely because the same “lost communication” fault can be caused by simple connection issues, power/ground problems, network wiring faults, or a failed module. Final scope depends on confirmed test results, parts accessibility, and labor time.

• Clean, reseat, and secure yaw rate sensor module connectors; correct pin fit issues and restore proper terminal tension
• Repair or replace damaged wiring in the network circuits to the yaw rate sensor module (including chafing, opens, or shorted sections)
• Repair power supply or ground faults feeding the yaw rate sensor module (blown protection devices, loose grounds, high-resistance connections)
• Correct network backbone issues (splices, junctions, or connector damage affecting the communication bus shared with other modules)
• Replace the yaw rate sensor module only after confirming power/ground integrity and network circuits are good
• Perform required setup, calibration, or relearn procedures after repairs (varies by vehicle and may be mandatory after module replacement)
• Update or reprogram control modules if service information directs it after verifying hardware and wiring are not the cause

Can I Still Drive With U0123?

Driving with U0123 is sometimes possible, but it may reduce or disable stability-related functions that rely on yaw rate information, which can increase risk during abrupt maneuvers or low-traction conditions. If warning indicators for stability/traction, brake system, or steering are present, or if the vehicle enters a reduced-assist mode, avoid driving and have the network fault diagnosed. If the vehicle exhibits unsafe handling changes, do not continue driving.

What Happens If You Ignore U0123?

Ignoring U0123 can leave stability/traction features limited or unavailable, potentially extending stopping distance on slippery surfaces or reducing directional control during emergency maneuvers. Persistent communication faults can also mask other network issues, lead to additional warning messages, and complicate future diagnostics until the underlying wiring, power/ground, or module cause is corrected.

Last updated: March 16, 2026

Vehicles Commonly Affected by U0123

• Vehicles equipped with electronic stability control systems that use a dedicated yaw rate sensor module
• Vehicles where the yaw rate sensor module communicates over a shared in-vehicle network bus
• Vehicles with under-seat or floor-mounted sensor modules prone to connector disturbance during interior service (varies by vehicle)
• Vehicles operated in environments that increase corrosion risk at connectors and grounds (varies by vehicle)
• Vehicles with prior collision repair or underbody work where harness routing or splices may have been altered
• Vehicles with recent battery replacement, low-voltage events, or power distribution repairs affecting module wake-up and communication
• Vehicles with high harness flex areas or tight routing where chafing can develop over time
• Vehicles with multiple networked chassis modules where a single network fault can cascade into several U-codes

For best results, confirm the root cause with power/ground checks, network integrity testing, and verified module communication before replacing the yaw rate sensor module.