P0600 Engine computer lost communication with another module

Serial communication link malfunction

P0600 in short

P0600 means the engine computer has lost communication with one or more other control modules. Low battery voltage and wiring faults are common causes, with a faulty computer less common. Effects range from a warning light to shifting problems or no-start, so have it diagnosed soon.

Control modules share data over a network. If the engine computer cannot reach another module, it sets P0600, and the code does not say which module.

PartsAvatar warns that low battery voltage is often mistaken for a failed computer. Both sources list wiring faults, corrosion and poor connections, PCM software and a failed PCM.

Symptoms depend on which module is silent: warning lights for ABS and traction control, shifting problems, no-start or limp mode.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Low battery voltage

    Common general cause
    Why it ranks here
    PartsAvatar names low battery voltage as the common misdiagnosis and cause.
    What would change this
    Rises if the battery tests weak or the code began after a flat battery. Falls if voltage is steady.

  2. Damaged, open, shorted or corroded data wiring and connectors

    Common general cause
    Why it ranks here
    Both sources list wiring and connection faults.
    What would change this
    Rises if other modules also report lost communication. Falls if the network tests normal.

  3. PCM software issue or failed computer

    Possible — needs testing
    Why it ranks here
    KBB lists PCM software and a defective PCM, and PartsAvatar lists replacing the ECU or PCM.
    What would change this
    Rises after power and wiring test good and a reflash does not help.
    How to test the engine control module (ecm / pcm)

What to test first

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

  1. Read all codes from every module, not just the engine, and note any U-codes or ABS and transmission codes.

    Low riskTool: scan tool that reads all modules

    • IfSeveral modules show communication or voltage codes

      It meansCheck battery and wiring first.

      Go to step 2

    • IfOnly P0600 is stored

      It meansStill start with battery and wiring.

      Go to step 2

  2. Have the battery and charging system tested and the data wiring and connectors inspected.

    Best left to a shopTool: battery tester, multimeter

    Warning:Testing live network wiring can damage modules. Let a shop do it.

Symptoms

  • Check engine light on
  • ABS and traction control lights on
  • Shifting problems or reduced economy
  • Stalling, no-start or limp mode Gets more serious: stop and have it checked.

How to fix

  1. Have the battery tested and the terminals checked; low voltage is a common cause.

Parts and cost context

  • Engine control module (ECM / PCM):Replacing the computer is the last step; wiring or battery faults produce the same symptoms. 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

Subaru

  • 2005–2006 · Legacy

    Supported by vehicle data

    A Subaru bulletin (also covering Outback and B9 Tribeca) names P0600 with B0221 and/or B0223. Only the NHTSA summary was read, so the repair is not stated and the bulletin is not verified as current.

  • 118106Status unverified

    DTC P0600, B0221 and/or B0223

    2005–2006legacy, outback, b9-tribeca · issued · NHTSA 10020717

    Subaru service information whose title names P0600 with B0221 and/or B0223. The NHTSA summary does not state the repair.

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

Ford

  • 2021 · F-150

    Supported by vehicle data

    Ford TSB 21-2086 reprograms the PCM for P0600 (with P060B and/or P0607) on early-build 2021 F-150 3.3L. Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • TSB 21-2086Status unverified

    MIL with P060B, P0600 and/or P0607 (3.3L Duratec)

    2021f-150 · NHTSA 10189791

    2021 F-150 with the 3.3L Duratec built on or before 2 Mar 2021: various PCM software parameters may set these codes; reprogram the PCM.

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

Land Rover

  • 2014–2015 · Range Rover Evoque

    Supported by vehicle data

    Land Rover bulletin LTB00740NAS1 lists P0600-04 in the transmission control module with a gearbox fault message on the Evoque. Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • LTB00740NAS1Status unverified

    Gearbox fault message with P0600-04 and other TCM codes

    2014–2015range-rover-evoque · NHTSA 10105428

    A gearbox fault message may show with P0600-04 and other codes stored in the transmission control module. The summary excerpt does not state the repair.

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

  • P0606A control module found a fault in its own processor or programming

    Same system Possible — needs testing

    Both are engine computer fault codes; check power, grounds and software for either.

All Engine computer (ECM/PCM) codes

P0600 questions

Does P0600 mean I need a new computer?

Often not. Low battery voltage and wiring faults produce the same code, so those are tested first.

Sources and review

  1. P0600 Code: Serial Communication Link — Kelley Blue Book
  2. P0600 Serial Communication Link Malfunction — PartsAvatar
  3. Subaru bulletin 118106: DTC P0600, B0221 and/or B0223 — Subaru (via NHTSA flat file) ,
  4. Ford bulletin TSB 21-2086: MIL with P060B, P0600 and/or P0607 (3.3L Duratec) — Ford (via NHTSA flat file)
  5. Land-Rover bulletin LTB00740NAS1: Gearbox fault message with P0600-04 and other TCM codes — Land-Rover (via NHTSA flat file)
Last reviewed
Written by
Saurabh K.
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