P06E4: Control Module Wake-up Circuit Performance
What to do
Mention whether the battery goes flat when the car is left standing for a few days. That is the commonest sign of this fault — a module being held awake instead of going to sleep — and it is genuinely useful information because it points diagnosis straight at the cause.
Also mention anything electrical that works intermittently or seems dead until you use something else first. That is the opposite half of the same fault.
Mention any damp in the car — a wet footwell, a boot that smells musty, a blocked sunroof or scuttle drain. Water in a connector is a classic cause of a module being held awake, because it leaks just enough current to look like a wake signal.
Mention any accessories fitted after purchase, such as a dashcam, tracker or alarm, since those are frequently wired to permanent supplies and interfere with sleep.
What this code means
The circuit that wakes a control module from sleep is not performing correctly.
Every module on a modern vehicle sleeps, and understanding why explains this code. A car parked for a fortnight must still start. With dozens of modules each drawing even a small current, a vehicle that never slept would flatten its battery in days — so modules shut down to microamps and are woken by a signal when needed.
Wake-up happens by several routes: a door handle touched, the key approaching, a bus message, or a hard-wired wake line from a gateway. This code says that route is not working as it should.
The two failure directions have completely different symptoms, and identifying which is happening is the whole diagnosis.
- Failure to wake. A module stays asleep when it should be awake, so a system is simply dead until something else wakes it. The classic report is 'it works sometimes' — the module woke by another route on those occasions.
- Failure to sleep. The circuit holds the module awake, and the battery goes flat over a few days of standing. This is by far the more noticeable of the two.
A parasitic drain complaint with this code stored is not a coincidence. Read this code as the likely cause and check what is holding the wake line active rather than hunting fuses at random.
Water in a connector is the classic cause of a permanently held wake line, because it provides exactly the small leakage current a wake input responds to.
Likely causes
Start here
- Water ingress into connector · easy
- Corroded or loose connector · easy
- Parasitic drain from an accessory · moderate
Less common
- Damaged data bus wiring · moderate
- Control module software fault · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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