U0001 A module reports a fault on the high-speed CAN bus itself, the main data network that links the engine, transmission, brake and steering computers

High-speed CAN communication bus fault

U0001 in short

U0001 means a module saw a problem on the high-speed CAN bus, the network linking the engine, transmission, brake and steering computers. Common causes are network wiring or connectors, low battery voltage or module software. It can affect shifting and steering assist, so have it diagnosed soon.

Modern cars share data over a high-speed CAN bus, a pair of twisted wires. Chrysler, Jeep, Dodge and Ram call it the CAN C bus. U0001 means a module could not use that bus properly: messages were missing, corrupted or the module dropped off the bus.

Unlike lost-communication codes such as U0100, U0001 points at the bus itself rather than one silent module. Suffixes add detail; Land Rover uses -82 for an alive or sequence counter fault and -87/-88 for missing messages.

Several FCA bulletins fix U0001 in the transmission computer with a software update. Otherwise, check the battery and the bus wiring, including the star connector where branches join, before blaming a module.

Most likely causes

  1. Network wiring or connector fault, including a star connector

    Supported by vehicle data
    Why it ranks here
    Owners report dealers tying U0001 to the CAN C star connector on a 2023 Wrangler and a 2018 Pacifica, and Land Rover lists harness faults for U0001 with heavy steering.
    What would change this
    Rises if the codes come and go with bumps or moisture, or bus resistance is wrong. Falls if the bus reads about 60 ohms with clean signals.

  2. Transmission or ABS module software

    Supported by vehicle data
    Why it ranks here
    FCA bulletins reprogram the transmission computer for U0001 on the 2015 Chrysler 200 and Jeep Cherokee and the 2016-2017 Renegade, and the ABS module on the Fiat 500e.
    What would change this
    Rises if a bulletin covers your VIN and the code sits in the transmission or ABS module.
    How to test the transmission control module (tcm)

  3. Low battery voltage

    Supported by vehicle data
    Why it ranks here
    Land Rover names low battery voltage for U0001 with steering faults, and a Ram owner was told U0001 indicated low voltage.
    What would change this
    Rises if the battery tests weak or the code followed a dead battery. Falls with a healthy battery and charging system.

  4. A failing module disturbing the bus

    Possible — needs testing
    Why it ranks here
    An owner reports U0001 with a failed power steering module code on a 2015 Challenger; one bad module can upset the whole bus.
    What would change this
    Rises if the bus recovers when one module is unplugged.

  5. Code set by plugging in a diagnostic tool with the ignition on

    Possible — needs testing
    Why it ranks here
    Harley-Davidson traced historic U0001 codes to connecting a diagnostic module with the ignition on. That bulletin is for motorcycles, so treat this as a possibility only.
    What would change this
    Rises if U0001 is history only, with no symptoms, after diagnostic work.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Scan every module and note which ones stored U0001, the suffix, and other U-codes stored with it.

    Low riskTool: scan tool that reads all modules

  2. Ask a dealer to check your VIN for module software updates that mention U0001.

    Low risk

  3. Test the battery and charging system and check that terminals and grounds are clean and tight.

    Low riskTool: battery tester

  4. Have a shop measure CAN high to CAN low resistance with the battery disconnected, check for about 2.5 V on each line with the key on, and inspect the star connector.

    Best left to a shopTool: multimeter

    Warning:Probing network connectors can damage terminals; leave it to a technician.

Symptoms

  • Check engine light on
  • Several warning lights at once, gauges cutting in and out
  • Transmission will not shift, stuck in Park or Shift Denied Gets more serious: stop and have it checked.
  • Power steering lost Gets more serious: stop and have it checked.
  • Hesitation or loss of power Gets more serious: stop and have it checked.
  • 4WD or AWD unavailable message

How to fix

  1. Have the battery tested and check that terminals and grounds are clean and tight.

  2. Write down every code from every module before anything is cleared.

  3. Ask a dealer whether your VIN has a software bulletin for U0001.

Parts and cost context

  • transmission computer:FCA fixes several U0001 cases with a software update, not a new part. Labour varies; get a quote.
  • CAN star connector or harness:Repairs vary from cleaning a connector to replacing a harness section. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Jeep

  • 2016–2017 · Renegade

    Supported by vehicle data

    FCA 21-011-17 and 21-043-17 reprogram the transmission computer for U0001. Whether they are still current is not verified.

  • 2015–2017 · Cherokee

    Supported by vehicle data

    FCA 21-019-17 covers 2015 models with U0001 in the transmission computer; owners report shifting faults and engine cut-outs. Whether the bulletin is still current is not verified.

  • 2023 · Wrangler

    Supported by vehicle data

    An owner reports U0001 with several other U-codes and lost power steering, which the dealer tied to the CAN C star connector.

  • 21-011-17Status unverified

    Transmission diagnostic and shift enhancements

    2016renegade · issued · NHTSA 10140039

    Reprogram the transmission computer for U1412, U0001 and P0887.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 21-043-17Status unverified

    Transmission diagnostic and shift enhancements

    2017renegade · issued · NHTSA 10121811

    Reprogram the transmission computer; U0001 is the shifter module CAN bus-off code.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chrysler

  • 2015 · 200

    Supported by vehicle data

    FCA 21-019-17: transmission computer update with U0001 among the codes. Whether it is still current is not verified.

  • 21-019-17 REV. AStatus unverified

    Transmission diagnostic and shift enhancements

    2015200 · issued · NHTSA 10121787

    Reprogram the transmission computer; U0001 among the codes. Also covers 2015 Jeep Cherokee.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Land Rover

  • 2014 · Range Rover Sport

    Supported by vehicle data

    Land Rover LTB00677: stuck in Park with U0001-81. Whether it is still current is not verified.

  • LTB00677NAS1Status unverified

    Unable to shift from Park with U0001-81

    2014range-rover-sport · issued · NHTSA 10101662

    Gearbox Fault with U0001-81 in the TCM and ABS module and U0402-2A.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM73424Status unverified

    U0001-82 stored in the ABS module

    2013–2017range-rover, range-rover-sport, discovery · issued · NHTSA 10116980

    Covers U0001-82 alive/sequence counter codes found in the ABS module.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • LTB00911NAS1Status unverified

    Two Wheel Drive Only fault

    2014–2016discovery-sport, range-rover-evoque · issued · NHTSA 10105743

    U0001 codes in the AWD module with a Two Wheel Drive Only message.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • U0420A module received implausible data from the power steering control module

    Shares causes Supported by vehicle data

    Land Rover SSM71278 lists U0001-87/88 with U0420-68 in heavy-steering cases.

  • U3003Manufacturer code: on Ford, Lincoln, Mazda and Honda, the module that stored it saw its battery supply voltage outside the allowed range, usually too low

    Shares causes Supported by vehicle data

    Land Rover SSM71278 lists U0001 with U3003-62; low battery voltage is a named cause.

  • U0402A module received invalid data from the transmission computer

    Shares causes Supported by vehicle data

    Land Rover LTB00677 lists U0001-81 with U0402 when the Range Rover Sport cannot shift from Park.

  • U0401A module received invalid data from the engine or powertrain computer

    Shares causes Supported by vehicle data

    FCA 21-019-17 lists U0001 and U0401 in the transmission computer, fixed by the same software update.

  • U0151Lost communication with the restraints (airbag) control module

    Same system Possible — needs testing

    An owner reports U0001 with U0151, U0155 and U0418 on a 2023 Wrangler, all tied to the CAN C star connector.

  • U0155Lost communication with the instrument panel cluster

    Same system Possible — needs testing

    An owner reports U0001 with U0155 on a 2023 Wrangler, tied to the CAN C star connector.

All Module network (CAN bus) communication codes

U0001 questions

How is U0001 different from U0100?

U0100 means modules lost contact with the engine computer. U0001 means a module saw a fault on the high-speed bus itself, so the wiring, the battery or a module upsetting the network are the first suspects.

Can a software update fix U0001?

On some vehicles, yes. FCA bulletins reprogram the transmission computer for U0001 on the 2015 Chrysler 200 and Jeep Cherokee and the 2016-2017 Renegade.

Sources and review

  1. FCA 21-019-17 Rev. A: transmission diagnostic and shift enhancements (2015 Chrysler 200, Jeep Cherokee) — FCA US LLC / NHTSA ,
  2. Land Rover SSM73424: U0001-82 stored in the ABS module (2013-2017) — Jaguar Land Rover North America / NHTSA ,
  3. NHTSA complaint 11540831: 2023 Jeep Wrangler CAN C star connector, U0151 and U0155 — NHTSA Office of Defects Investigation
  4. NHTSA complaint 11155145: 2015 Jeep Cherokee will not shift with U0001 — NHTSA Office of Defects Investigation
  5. NHTSA complaint 11523399: 2020 Jeep Gladiator stuck in Park, no power steering, U0001 — NHTSA Office of Defects Investigation
  6. NHTSA complaint 11091931: 2015 Dodge Challenger no power steering with U0001-00 — NHTSA Office of Defects Investigation
  7. Land Rover LTB00677: unable to shift from Park with U0001-81 (2014 Range Rover Sport) — Jaguar Land Rover North America / NHTSA ,
  8. NHTSA complaint 11733578: 2018 Chrysler Pacifica Hybrid CAN star connector failure — NHTSA Office of Defects Investigation
  9. Land Rover SSM71278: heavy steering with EPAS and CAN DTCs (2012-2016) — Jaguar Land Rover North America / NHTSA ,
  10. ASE L1 study guide: Network U-codes — Open Exam Prep
  11. FCA 21-011-17: transmission diagnostic and shift enhancements (2016 Jeep Renegade) — FCA US LLC / NHTSA ,
  12. FCA 21-043-17: transmission diagnostic and shift enhancements (2017 Jeep Renegade) — FCA US LLC / NHTSA ,
  13. FCA 08-045-16: ABS module system enhancements (2013-2015 Fiat 500, 500e) — FCA US LLC / NHTSA ,
  14. NHTSA complaint 11724761: 2017 Ram 1500 service transmission light with U0001 and U0402 — NHTSA Office of Defects Investigation
  15. Harley-Davidson TA0015: MY17 ABS historic DTCs U0001 and U0003 — Harley-Davidson / NHTSA ,
  16. NHTSA complaint 11365842: 2017 Jeep Cherokee shifter fault with U0001 CAN C bus — NHTSA Office of Defects Investigation
Last reviewed
Written by
Saurabh K.
Editorial review
Pending
Technician review
Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

My Car

Pick your car and code pages will point out notes and bulletins for it. Saved only in this browser.

Fill this in from your VIN

Used once to identify your engine; not stored.