P0605

What it means

P0605 is the generic code for an Internal Control Module Read Only Memory (ROM) error. The engine or powertrain control unit runs self-checks on its stored program and calibration data at start-up and while running. If that check fails or the data cannot be read correctly, it sets this code, and it may then run in a reduced-function mode.

Symptoms

• Malfunction indicator lamp on
• Engine in limp mode or reduced power
• Engine cranks but fails to start, or starts and stalls
• Poor or erratic running, hesitation or rough idle
• Gearbox stuck in one gear or shifting harshly (where the gearbox is controlled by the same unit)
• Other warning lamps on, or other control units reporting communication faults

Possible causes

• Internal fault in the control unit memory or processorlikely
• Low or unstable supply voltage to the control unit from a weak battery or poor chargingpossible
• Poor power or earth connections to the control unit, including corroded or loose terminalspossible
• Failed or interrupted software update or calibration flash leaving corrupt datapossible
• Outdated or faulty calibration in the control unit, where the manufacturer has issued a correctionrare
• Water ingress, heat or physical damage to the control unitrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, looking for voltage or communication faults alongside P0605
2. Check battery condition and charging voltage, as low voltage can corrupt control unit self-tests
3. Inspect the control unit connectors, power feeds, fuses and earth points for corrosion, looseness, damage or water
4. Clear the code, then road test and recheck to see whether it returns immediately or only intermittently
5. Check whether the software or calibration is the latest version for the vehicle, and whether any bulletins apply to that model and engine
6. Check for any recent software updates, previous repairs or battery disconnections that could explain corrupt data
7. Check the control unit for signs of water, heat or impact damage

How to fix

• Repair or replace damaged wiring, connectors, fuses or earth connections feeding the control unit
• Replace or recharge a weak battery and repair any charging system fault
• Reload the correct software or calibration if the data is corrupt or outdated and the manufacturer lists this as a fix
• Repair or replace the control unit if the fault remains, and have it coded and programmed to the vehicle as the model requires
• Dry out and repair the source of any water leak affecting the control unit, replacing the unit if it is damaged

Can I keep driving?

This code for other makes

• P0605AudiLack of proper voltage and or ground to the PCM, Defective PCM ROM memory module, Defective PCM ground circuit(s), Defective PCM controlled output devices

Nearby codes

• P0604GenericInternal Control Module Random Access Memory (RAM) Error
• P0606GenericControl Module Processor