P0605 The engine computer failed its own read-only memory check

Internal control module ROM error / ECM or PCM memory error

P0605 in short

P0605 means the engine or powertrain computer found a fault in its read-only memory, where its program and calibrations are stored. Low voltage or a failed update can corrupt it; a faulty module is the other cause. Get it checked soon, and stop driving if it stalls or drops into limp mode.

The engine computer keeps its program in memory that should not change. At start-up it adds up the stored data and compares the result with a reference value. If they do not match, it sets P0605.

Voltage spikes, a failed software update, a weak battery, water in the connectors or poor grounds can all damage or disturb that memory. A computer worn out by heat and age can do the same.

Because the computer controls fuelling, spark and often the transmission, the effects range from only a light to hard starting, stalling, shift problems and limp mode.

Most likely causes

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

  1. Low voltage, poor ground or damaged module wiring

    Common general cause
    Why it ranks here
    Unanswered lists weak battery, loose grounds, corrosion and water in connectors as causes, and advises fixing electrical faults before replacing the module.
    What would change this
    Rises if the battery tests weak, voltage at the module is outside about 12.0 to 14.8 volts, or connectors are corroded. Falls if power, grounds and connectors are all sound.
    How to test the engine control module (ecm / pcm)

  2. Corrupted or outdated engine computer software

    Common general cause
    Why it ranks here
    The checksum failure means the stored program no longer matches what the module expects, and reflashing the latest OEM software is one of the repairs Unanswered lists. Causes include a failed update and aftermarket tuning.
    What would change this
    Rises if the code followed a software update, battery disconnect or tune. Falls if a dealer reflash does not clear it.
    How to test the engine control module (ecm / pcm)

  3. Failed engine or powertrain computer

    Possible — needs testing
    Why it ranks here
    Replacement is listed only after electrical and software causes are ruled out and the memory is confirmed damaged.
    What would change this
    Rises if the code returns after power, grounds and reflash are verified good. Falls if any earlier step clears it.
    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 every stored code and the freeze-frame data with a scan tool, and note any communication or voltage codes stored with P0605.

    Low riskTool: OBD-II scan tool

    • IfLow-voltage or communication codes are stored too

      It meansFix the power supply first.

      Go to step 2

    • IfP0605 is the only code

      It meansCheck module power and grounds, then software.

      Go to step 2

  2. Have the battery, charging voltage, module power feeds, grounds and connectors checked for weak voltage, corrosion or water.

    Best left to a shopTool: multimeter, battery tester

    Warning:Testing live module circuits can short wiring and damage the computer. Let a shop do it.

  3. Ask a dealer whether the engine computer can be reflashed with the latest software for your VIN, then clear the code.

    Best left to a shopTool: dealer scan tool

    Warning:Reflashing a computer with a weak battery can leave it unusable. Let a dealer do it with a battery support unit.

Symptoms

  • Check engine light on
  • Hard starting or no-start
  • Shifting problems or reduced fuel economy
  • Stalling, sudden power loss or limp mode Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

  1. Check that the battery terminals are clean and tight, and have the battery tested.

  2. Ask a dealer whether a software update for the engine computer applies to your VIN.

Parts and cost context

  • Engine control module (ECM / PCM):Replacement is a last step after power, grounds and software are ruled out, and the new module usually has to be programmed to the car. 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

Hyundai

  • 2010 · Genesis Coupe

    Supported by vehicle data

    Hyundai's ECM update bulletin covers P0605 on the 2010 Genesis Coupe. Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • TSB-09-FL-09Status unverified

    ECM update for P0605 or slow rpm drop on throttle release

    2010genesis-coupe · NHTSA 10031948

    Engine computer (ECM) update for DTC P0605 or a slow rpm drop when the throttle is released.

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

Nissan

  • 2009–2013 · 370Z

    Supported by vehicle data

    Nissan bulletin NTB13-039 links P0605 to cruise control that will not set (370Z, Xterra, Titan, GT-R, Maxima and others). Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • 2002–2005 · Altima

    Supported by vehicle data

    Nissan bulletin 05053 lists P0605 among several codes for a lit MIL on the Altima. Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • NTB13-039Status unverified

    Cruise control will not set and DTC P0605 is stored

    2009–2013370z, xterra, titan, gt-r, maxima · NHTSA 10051768

    Nissan bulletin for cruise control that will not set with P0605 stored. 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.

  • 05053Status unverified

    MIL on with DTCs P0444, P0447, P0605, P1122, P1444, P1490

    2002–2005altima · NHTSA 10017563

    Nissan bulletin for a lit MIL with P0605 among several stored codes. The summary does not state the repair.

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

Infiniti

  • 2009–2011 · G37

    Supported by vehicle data

    Infiniti bulletin ITB-13-13 links P0605 to cruise control that will not set. Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • ITB-13-13Status unverified

    Cruise control will not set and DTC P0605 is stored

    2009–2011ex35, g37, qx56, m35, m45 · NHTSA 10051766

    Infiniti bulletin for cruise control that will not set with P0605 stored. 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

  • 1997–2003 · F-250 Super Duty

    Supported by vehicle data

    Ford bulletin 17571 covers a lit MIL with P0605 on older F-Super Duty trucks (1997-2003). Only the NHTSA summary was read; whether the bulletin is still current is not verified.

  • 17571Status unverified

    MIL on with P0603 or P0605 (Super Duty and others)

    1997–2003f-250-super-duty · NHTSA 10008134

    Ford bulletin for a lit MIL with P0603 (keep alive memory error) or P0605 (PCM read-only memory error) on 1997-2003 Super Duty trucks. The summary 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 Common general cause

    Both codes report a fault inside the engine computer itself. Check power, grounds and software for either.

  • P0607A control module failed one of its internal performance checks

    Same system Possible — needs testing

    P0607 is also an internal control-module fault code, often investigated with the same power and software checks.

All Engine computer (ECM/PCM) codes

P0605 questions

Can I drive with P0605?

It depends on the effect. If the car drives normally, get it checked soon. If it stalls, loses power or goes into limp mode, stop driving and arrange a tow.

Do I need a new computer for P0605?

Not at first. Low voltage, poor grounds and outdated software can set it, so a shop checks those and tries a reflash before replacing the module.

Sources and review

  1. P0605 Internal Control Module Read Only Memory (ROM) Error — The Automotive Technician (TaT)
  2. What the P0605 Code Means — unanswered.io
  3. Hyundai bulletin TSB-09-FL-09: ECM update for P0605 or slow rpm drop on throttle release — Hyundai (via NHTSA flat file)
  4. Nissan bulletin NTB13-039: Cruise control will not set and DTC P0605 is stored — Nissan (via NHTSA flat file)
  5. Infiniti bulletin ITB-13-13: Cruise control will not set and DTC P0605 is stored — Infiniti (via NHTSA flat file)
  6. Ford bulletin 17571: MIL on with P0603 or P0605 (Super Duty and others) — Ford (via NHTSA flat file)
  7. Nissan bulletin 05053: MIL on with DTCs P0444, P0447, P0605, P1122, P1444, P1490 — Nissan (via NHTSA flat file)
Last reviewed
Written by
Saurabh K.
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