By iCarsoft Official Store Technical Team, Automotive Diagnostics Editors · Updated October 14, 2026 · Technical sources checked
Quick Answer
U012A is documented by JLR for a 2013MY Range Rover L405 receiver that lost CAN messages from CHCM A after battery disconnection. It does not prove a battery or suspension failure; confirm model year and module fitment before testing.
What Does the U012A Code Mean?
U012A-00 is documented in JLR SSM69398 as a receiver-side loss of messages from Chassis Control Module A in a specific 2013MY Range Rover L405 application. The full fault record determines the test branch.
The useful diagnostic distinction in SSM69398 is between the code stored by a receiving module and the state of the sender. The bulletin describes a battery-supply disconnection followed by a chassis-control module that may not complete its power-up sequence; other controllers then record that they cannot receive the expected CHCM messages. That sequence is different from evidence that the suspension actuator, compressor, valve block, or steering hardware has failed.
First establish which module reported U012A-00, whether CHCM A is visible to the approved JLR scan tool, and whether the fault is current or historical. The same notice identifies an optional CHCMB on this application, so a scan report that names both chassis modules must be interpreted against the installed equipment rather than a generic network diagram.
Model-year control matters: the notice separates 2013MY L405 from 2014MY L405 and L494, where U0001-87 may be used instead. A matching label on another Range Rover therefore cannot be treated as proof of the same wake-up sequence. Use the receiver record, sender availability, supply and wake evidence together before selecting a module or suspension branch.
The primary JLR evidence separates receiver memory from sender availability: U012A-00 can be recorded after a battery-supply interruption when CHCM A fails to complete power-up. That makes the first branch a state and supply investigation, not an automatic controller replacement.
The bounded JLR example is a 2013MY Range Rover L405 after battery-supply disconnection: receivers may log U012A-00 when CHCM A does not power up correctly. It is application evidence, not a universal threshold, topology, or replacement instruction; preserve the model-year and optional-CHCMB limits.
For a practical decision, preserve the full scan before clearing and ask whether the event followed the documented battery-reconnection condition. If CHCM A is now visible and only a stored communication record remains, continue with the VIN-specific JLR functional checks rather than authorizing a suspension part. If CHCM A remains unavailable, test its approved feed, ground, wake state, connector and network branch in the required operating state.
Treat a returned scan session as communication evidence only; suspension or adaptive-dynamics warnings still need their own safety verification.
Save the full module wording and suffix before clearing; they can change the test path.
Separate U012A from adjacent fault families
| Code | General description | Key distinction |
|---|---|---|
| U012A | Lost Communication with Chassis Control Module A | This guide concerns the named controller message path. |
| U0073 | Control Module Communication Bus A Off | A bus-off result is a different network condition; confirm the actual fault record. |
| U0140 | Lost Communication with Body Control Module | A body-network code is not interchangeable with this module-specific result. |
Record the complete U012A description. The suffix, reporting module and companion faults can change the diagnostic path. Use the manufacturer's full wording and test procedure for the exact vehicle.
U012A Symptoms and Likely Causes
Record U012A symptoms and fault status; symptoms alone cannot identify a failed part.
Check whether companion faults share a proven cause.
Record the exact warning, when it appeared and which function changed; it is evidence, not proof of a failed controller.
Compare saved multi-module reports with supported live data; unavailable data does not identify the cause.
Preserve service history and inspect the disturbed branch first while treating timing as a clue.
Save every module's codes and status; a shared supply or network code can change the diagnostic order.
Practical cause-checking order
- Low-voltage supply, ground or wake-state loss at the Chassis Control Module A: Compare the recorded battery interruption with current CHCM A power-up and receiver status before attributing the event to a failed module.
- Open, shorted, corroded or chafed CAN wiring or connector terminals: Require connector or network-branch evidence from the correct diagram; the communication timeout does not identify a damaged wire by itself.
- Gateway routing, termination or configuration/software condition: Confirm the installed route and configuration before treating a gateway or software condition as the cause.
- The controller is asleep, isolated or unavailable during service: Use service history and the required operating state to distinguish an unavailable controller from an uninstalled optional CHCMB.
- Internal controller fault only after external communication checks pass: Consider internal CHCM failure only when the applicable external and communication checks support that conclusion.
Did U012A appear after recent battery reconnection, chassis-control or harness work? Recheck the documented connections, parts and setup steps affected by that work. Record battery and software history; a post-repair code does not prove the new part is defective.
How Serious Is U012A, and Can You Drive?
Suspension and adaptive-dynamics warnings in the notice can affect vehicle behavior; follow the vehicle manual and do not treat a communication return as proof of ride-height or handling readiness. Follow the owner manual and all vehicle warnings. U012A does not establish a safe remaining driving distance. Stop safely and arrange qualified inspection or towing for abnormal function; do not use a successful scan as permission to bypass a warning.
Record warning messages, operating conditions and service history. Do not induce wheel slip, emergency braking or a handling event on public roads. A red stop warning or abnormal control overrides any verification plan.
Stop and arrange a tow if steering, braking, propulsion, charging, parking-brake or other safety behavior is abnormal.
Follow the vehicle-specific electrical, steering, suspension or driveline safety precautions. Do not bypass interlocks or command powered safety components outside the approved procedure.
How to Diagnose U012A in the Right Order
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Identify the application and preserve evidence
Save the reporting receiver, U012A-00 status, companion network records and the exact suspension or adaptive-dynamics warnings before clearing anything.
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Inspect the relevant physical and electrical path
Confirm the VIN and model year are the 2013MY Range Rover L405 application; identify CHCM A and record whether the optional CHCMB is installed.
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Confirm architecture and prerequisites
Record the battery-supply disconnection or reconnection history, and keep the bulletin’s 2014MY L405/L494 U0001-87 note separate from this code.
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Separate network behavior from system behavior
Check the approved CHCM A supply, ground, wake and connector conditions in the specified state; do not infer a compressor, valve or actuator fault from the timeout.
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Prove the repair path before parts
Use the JLR service tool to compare the receiving module’s record with current CHCM visibility and distinguish a completed power-up issue from a persistent network loss.
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Verify the original condition after repair
After the demonstrated branch is corrected, complete the VIN-specific communication and suspension or adaptive-dynamics functional checks and document any warning that remains.
Specifications are vehicle-specific. Use the exact VIN specifications, approved test points and required operating state. No generic value or drive cycle can replace the applicable procedure. Manufacturer examples here do not establish specifications for other applications.
U012A Repairs and Cost Planning
A U012A repair must address the demonstrated failure. Do not replace an assembly from the code alone.
Recheck installation and required setup after repair. The application boundary is material: SSM69398 covers 2013MY Range Rover L405 and identifies optional CHCMB; it separately notes U0001-87 for 2014MY L405/L494. Record VIN, model year, installed module and reporting receiver before using the bulletin.
Ask the shop to name the failed branch and the measurement supporting each proposed repair.
Authorize diagnosis before parts while the cause remains uncertain.
| Possible path | Quote basis |
|---|---|
| Repair the demonstrated power, ground, connector, harness, gateway or network branch | VIN-specific quote |
| Restore configuration, software or required setup only through the VIN-specific procedure | VIN-specific quote |
| Replace the isolated controller or assembly only after external evidence and the OEM test support that path | VIN-specific quote |
These are alternative repair paths, not prices to add together. Request a VIN-specific quote separating diagnosis, parts, labor, fluids, taxes, required setup and verification. Ask which failed test supports the proposed repair and whether warranty coverage applies.
Using iCarsoft CR Pro S for U012A
On a supported vehicle, iCarsoft CR Pro S can save accessible faults, available freeze frame, live data and diagnostic reports. Preserve the U012A evidence before clearing.
Compare the saved and final module records. Scan data supports diagnosis but does not replace the OEM reference, physical measurement or safety-system functional check.
Preserve the chassis-control module A power, ground, wake and CAN path evidence
iCarsoft CR Pro S
Review supported codes and relevant live data together. Confirm the exact VIN, controller access, PIDs and any requested active test with iCarsoft before purchase; generic product capabilities do not guarantee a U012A-specific function.
Check current CR Pro S price and availabilityCheck CR Pro S compatibility by VINThe official product page describes supported full-system diagnostics, available live data, freeze frame and diagnostic reports; exact controller coverage and active tests depend on the VIN and software. Confirm the requested function by VIN before purchase. Follow OEM prerequisites and stop for abnormal operation.
Know the measurement boundary. Scan data describes ECU-provided information; it does not directly prove the physical condition of the chassis-control module A power, ground, wake and CAN path. Where required, use approved multi-module scan access, wiring diagram, voltage-drop/continuity tools and the VIN-specific network procedure and compare reported values with the relevant measured evidence.
Verify the U012A Repair
After repair, verify installation, clearance and required setup. Save the final findings and clear only erasable records as instructed. Battery disconnection is not a repair.
Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the chassis-control module A power, ground, wake and CAN path, and check current and pending faults in related modules. A clean start or idle period does not prove the repair; use the OEM functional check for the affected system.
Compare the original and final fault status. Record the functional-check result and whether the original event returned.
If U012A returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Confirm the prescribed affected-system functional verification separately from code clearing.
Verification follows the system involved. After saving the original evidence, use the OEM procedure to clear erasable records, complete any required calibration or functional check, and compare the final module status with the original warning and fault conditions.
Related Chassis-Control Module A Power, Ground, Wake And CAN Path Code Guides
Compare the related monitor families below. Shared symptoms or components do not make their repair procedures interchangeable.
U012A Frequently Asked Questions
Does U012A prove the Chassis Control Module A is bad?
No. In the cited JLR case, U012A-00 is a receiver record after a battery-supply interruption and may reflect CHCM A power-up or message-path availability. Prove the VIN-specific feed, wake, connector, network branch and sender status before naming the module as failed; the code alone does not identify a suspension part.
What should I check first for U012A?
Save every module's codes and freeze frame before clearing. Confirm the full definition, suffix and VIN architecture. Then inspect recent battery reconnection, chassis-control or harness work, connectors and shared supplies. Those facts determine whether the next test needs approved multi-module scan access, wiring diagram, voltage-drop/continuity tools and the VIN-specific network procedure or a manufacturer-specific functional procedure.
Can I drive with the U012A code?
Suspension and adaptive-dynamics warnings in the notice can affect vehicle behavior; follow the vehicle manual and do not treat a communication return as proof of ride-height or handling readiness. Follow the owner manual and all vehicle warnings. U012A does not establish a safe remaining driving distance. Stop safely and arrange qualified inspection or towing for abnormal function; do not use a successful scan as permission to bypass a warning.
Why did U012A return after a part was replaced?
A replaced or reconnected battery can explain the timing without proving the battery is defective. Compare the pre-clear report, current CHCM visibility and suspension/adaptive-dynamics warnings; complete the affected-system functional check even if the communication record clears.
What should a U012A repair estimate include?
Ask for the failed-test evidence and a VIN-specific breakdown of diagnosis, parts, labor, taxes, required setup and verification. A code alone cannot establish the repair price.
Can CR Pro S diagnose and clear U012A?
On a supported vehicle, CR Pro S can organize available faults, freeze frame, live data and reports, and can clear erasable records after repair. Confirm exact ECU coverage. It cannot replace the OEM functional procedure or physical measurements for the chassis-control module A power, ground, wake and CAN path.
The iCarsoft Official Store Technical Team maintains the store's fault-code library. This guide organizes published technical references and verified product information; it does not document a hands-on test of a particular vehicle or claim an individual engineer's review.
Technical and cost references
- JLR SSM69398 — CHCM/CHCMB communication after battery reconnection. Primary-source terminology and bounded mechanism evidence; not a universal repair criterion.
- Subaru Electrical Systems Operation & Diagnosis Module 602. OEM training context for no-message communication faults; it does not set another vehicle’s topology or thresholds.
Product information: Official iCarsoft CR Pro S page.
Editorial note: General diagnostic education, not a substitute for the owner's manual, current VIN-specific service information or professional inspection. Test limits, procedures, coverage and costs vary. Related articles provide context; apply only the specifications and repair procedures that match the vehicle. No universal failure rate, repair price or outcome is implied.
