U1000 Manufacturer code: on Nissan and Infiniti a module saw an error on the CAN network; on older GM vehicles it is a Class 2 serial data fault

CAN or Class 2 network communication fault (manufacturer specific)

U1000 in short

On Nissan and Infiniti, U1000 means a module saw an error on the CAN network; on early-2000s GM cars it is a Class 2 data fault. The usual cause is wiring, grounds or one faulty module on the network, not the module that stored it. It can cause no-start or limp mode, so get it checked soon.

U1000 is a manufacturer code, so the make decides what it means. Nissan and Infiniti use it for a CAN communication error. GM used it on vehicles with the older Class 2 serial data line, roughly the early 2000s.

On Nissan and Infiniti, the module that stores U1000 is usually fine. It is reporting that something else on the network is wrong. Nissan says to diagnose U1000 before the other codes, because they are often side effects of the same network problem.

On GM Class 2 vehicles, U1000 often sits in history alongside other U-codes. GM warns that on some 2003-2005 Malibu, Grand Am and Alero models U1000 will not lead to a repair and should be set aside. On Cadillac CTS and SRX, it can follow an ignition feed or data wiring fault at the engine computer.

Pick your make

U1000 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Wiring, connector or ground fault on the CAN network

    Supported by vehicle data
    Why it ranks here
    Nissan's bulletin says U1000 points to a communication error outside the module that stored it, and the TechNews case study traced a distorted bus to missing engine computer grounds.
    What would change this
    Rises if several modules store U1000 and the bus resistance or voltage at the diagnostic connector is wrong. Falls if the bus reads about 60 ohms with a clean signal.

  2. Engine computer power, ground or connector fault

    Supported by vehicle data
    Why it ranks here
    GM traces Cadillac CTS/SRX no-crank with U1000 to the ECM ignition feed or Class 2 wiring, and a Nissan dealer found a burnt ECM connector behind U1000 on a 2016 Rogue.
    What would change this
    Rises if the engine computer loses power or ground, or its connector shows heat damage. Falls if power and grounds test good under load.
    How to test the engine control module (ecm / pcm)

  3. A known bulletin condition on your vehicle

    Supported by vehicle data
    Why it ranks here
    Nissan and GM bulletins cover U1000 on specific models: a harness splice on cold-soaked NV200s, an IPDM on the 2017 Armada, a reversed harness wire on the 2015 City Express, and NTB06-009 on 2002-2006 Nissans.
    What would change this
    Rises if your vehicle and symptoms match a bulletin. Falls if no bulletin covers your VIN.

  4. Another module on the network has failed or dropped off

    Supported by vehicle data
    Why it ranks here
    Dealers have tied U1000 to a transmission computer that stopped sending, a failed brake unit on a Leaf and an internally shorted engine computer on a Pathfinder.
    What would change this
    Rises if one module will not answer the scan tool, or the bus recovers when that module is unplugged.

  5. Stored in error or in history only (some GM models)

    Supported by vehicle data
    Why it ranks here
    GM says U1000 can be set in error on the 2004 Grand Prix and should be disregarded on some 2003-2005 Malibu, Grand Am and Alero models.
    What would change this
    Rises if U1000 is history only, nothing is wrong, and it does not return after clearing.

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 U1000, whether it is current or history, and which other codes are present.

    Low riskTool: scan tool that reads all modules

  2. Ask a dealer to check your VIN for bulletins that mention U1000.

    Low risk

  3. With the battery disconnected, measure resistance between pins 6 and 14 of the diagnostic connector.

    Use cautionTool: multimeter

    Warning:Disconnecting the battery can reset settings and needs a radio code on some cars. Keep tools off the battery terminals.

  4. Have a shop check engine computer power and grounds under load, inspect its connector for heat damage, and scope the bus for a clean signal near 2.5 V at rest.

    Best left to a shopTool: multimeter and oscilloscope

    Warning:Probing computer connectors can damage terminals or short circuits; leave it to a technician.

  5. Have a shop follow GM's Class 2 diagnostic strategy, including the ECM ignition feed and Class 2 wiring on Cadillac CTS and SRX.

    Best left to a shopTool: scan tool with GM coverage

    Warning:Probing computer and data line connectors can damage terminals; leave it to a technician.

Symptoms

  • Check engine light on
  • Engine cranks but will not start, or will not crank
  • Limp mode: little or no acceleration Gets more serious: stop and have it checked.
  • Transmission fail-safe or VDC/slip lights (Nissan)
  • Shifter locked in Park or warning lamps flickering (GM)
  • Service 4WD light with 4WD not working (GM trucks)
  • Instrument cluster stops working (GM)

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 bulletin for U1000.

Parts and cost context

  • engine computer:Do not replace the engine computer until wiring, power and grounds are proven good; Nissan's NV200 bulletin says not to replace it for that condition. A new computer usually needs programming. Labour varies; get a quote.
  • IPDM (Nissan power distribution module):Nissan replaces the IPDM on 2017 Armadas with P0090 and U1000. 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

Nissan

  • 2005 · Murano

    Supported by vehicle data

    An owner reports limp mode with U1000 CAN COMM CIRCUIT, fixed by the dealer applying NTB06-009. Whether the bulletin is still current is not verified.

  • 2013–2015 · NV200

    Supported by vehicle data

    Nissan NTB15022A: crank, no start after a cold soak with U1000; fix is a harness splice, not a new engine computer. Whether it is still current is not verified.

  • 2017 · Armada

    Supported by vehicle data

    Nissan NTB17-020: P0090 with U1000/U1001 calls for a new IPDM. Whether it is still current is not verified.

  • NTB06-009Status unverified

    MIL on with U1000 or U1010 in the engine computer

    2002–2006altima, maxima, murano, pathfinder, sentra, frontier, xterra, titan, armada, quest, 350z · issued · NHTSA 10019613

    Covers 2002-2006 Nissans with U1000 or U1010 in the engine computer; the repair was not read.

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

  • NTB10066AStatus unverified

    Diagnosing U1000, U1001, U1002, U1010

    2005–2015altima, rogue, murano, pathfinder, sentra, frontier, titan, leaf · issued · NHTSA 10192394

    Diagnose communication codes first; the module storing U1000 is usually fine and the fault is elsewhere on the CAN network.

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

  • NTB15022AStatus unverified

    Crank, no start after cold soak with U1000

    2013–2015nv200 · issued · NHTSA 10192568

    Splice specific EGI harness wiring; do not replace the engine computer.

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

  • NTB17-020Status unverified

    MIL on with P0090 and U1000/U1001

    2017armada · issued · NHTSA 10119192

    Replace the IPDM when P0090 is stored with U1000 or U1001.

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

Chevrolet

  • 2015 · City Express

    Supported by vehicle data

    Nissan-built van: crank, no start with U0100, U1000 and B2193 from a reversed EGI harness wire (GM 15169, PIT5369). Whether it is still current is not verified.

  • 15169Status unverified

    Crank, no start with U0100, U1000, B2193

    2015city-express · issued · NHTSA 10090110

    A reversed wire in the engine EGI harness stops spark at start-up; dealers revise the harness.

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

Cadillac

  • 2004–2009 · CTS

    Supported by vehicle data

    GM PIC5460B: no crank with U1000 in Class 2 modules, from the ECM ignition feed or Class 2 wiring (also SRX). Whether it is still current is not verified.

  • PIC5460BStatus unverified

    No crank or key will not release

    2004–2009cts, srx · issued · NHTSA 10113930

    Check the ECM Ignition 1 feed and Class 2 wiring; other modules may store U0100 or U1000.

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

Pontiac

  • 2003–2005 · Grand AM

    Supported by vehicle data

    GM PIC3557: disregard Class 2 U1000 (also Chevrolet Malibu). Whether it is still current is not verified.

  • PIC3557Status unverified

    Class 2 U1000 may not lead to a repair

    2003–2005grand-am · issued · NHTSA 10112621

    Disregard U1000 current or in history; also covers Chevrolet Malibu and Oldsmobile Alero.

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

  • U0100Lost communication with the engine or powertrain computer

    Shares causes Supported by vehicle data

    GM's 2015 City Express bulletins and the Cadillac CTS/SRX bulletin list U0100 and U1000 together, both caused by a fault at or near the engine computer.

All Module network (CAN bus) communication codes

U1000 questions

Should the module that stored U1000 be replaced?

Usually not. Nissan says a module reporting U1000 is typically working and the fault is elsewhere on the network. Its NV200 bulletin even says not to replace the engine computer.

Why does U1000 mean different things on Nissan and GM?

It is a manufacturer code. Nissan and Infiniti use it for a CAN network error; early-2000s GM vehicles used it for a Class 2 data line fault.

Sources and review

  1. Nissan NTB15022A: NV200 crank, no start after cold soak with U1000 — Nissan North America / NHTSA ,
  2. GM 15169: 2015 City Express crank, no start with U0100, U1000, B2193 — General Motors / NHTSA ,
  3. GM 030845004: intermittent warning lamps, no crank, U1000 and U1016 (2001-2004 Century, Regal) — General Motors / NHTSA ,
  4. NHTSA complaint 10150585: 2005 Nissan Murano limp mode with U1000 — NHTSA Office of Defects Investigation
  5. NHTSA complaint 10156996: 2005 Nissan Murano no acceleration with U1000 — NHTSA Office of Defects Investigation
  6. NHTSA complaint 11761244: 2015 Nissan Leaf brake failure with U1000 in ABS — NHTSA Office of Defects Investigation
  7. Nissan NTB10066A: service information for communication codes U1000, U1001, U1002, U1010 — Nissan North America / NHTSA ,
  8. The Infamous U1000 Code: A Study in Nissan Network Diagnostics — Nissan TechNews (Automotive Tech Info) ,
  9. ASE L1 study guide: Network U-codes — Open Exam Prep
  10. GM PIC5460B: no crank or key will not release, 2004-2009 Cadillac CTS and SRX — General Motors / NHTSA ,
  11. NHTSA complaint 11489161: 2016 Nissan Rogue no start, U1000 from no ECM communication — NHTSA Office of Defects Investigation
  12. Nissan NTB17-020: 2017 Armada MIL on with P0090 and U1000/U1001 — Nissan North America / NHTSA ,
  13. Nissan NTB06-009: MIL on with DTC U1000 or U1010 stored in ECU (2002-2006) — Nissan North America / NHTSA ,
  14. Infiniti 06004: MIL with U1000 or U1010 stored in ECU (2002-2006) — Infiniti / Nissan North America / NHTSA ,
  15. NHTSA complaint 10946177: 2011 Nissan Altima CVT fail-safe with U1000 — NHTSA Office of Defects Investigation
  16. GM 0308116001: DTC U1000, U1016, U1064, U1096 or U1305 set in error (2004 Grand Prix) — General Motors / NHTSA ,
  17. GM PIC3557: Class 2 DTC U1000 may not lead to a repair (2003-2005 Malibu, Grand Am, Alero) — General Motors / NHTSA ,
  18. GM bulletin 3154: Class 2 communications diagnostic strategy for DTC U1000 or U1255 — General Motors / NHTSA ,
  19. GM PIT5369: 2015 City Express crank, no start with U0100 and U1000 — General Motors / NHTSA ,
  20. GM 01267A: Service 4WD light on with no codes besides U1000 (2003-2004 trucks) — General Motors / NHTSA ,
  21. iATN TechMail: U1000 DTC (2001 Saturn L300) — International Automotive Technicians Network ,
  22. Infiniti ITB10029A: service information for communication codes U1000, U1001, U1002, U1010 — Infiniti / Nissan North America / NHTSA ,
  23. NHTSA complaint 10259771: 2005 Saturn L300 instrument cluster stopped working, U1000 — NHTSA Office of Defects Investigation
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Written by
Saurabh K.
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