U0422
NetworkInvalid Data Received From Body Control Module (BCM)
Most of the time this is a wiring or power supply problem rather than a dead module, which is the cheaper end of the scale. The code means another module on the car (the engine ECU, usually) is receiving data from the Body Control Module that doesn't make sense, so it flags the BCM as untrustworthy. The BCM runs your lights, locks, windows and a load of other body electrics, so when it starts sending rubbish down the CAN bus, those systems are the first to play up. Track down why the data is corrupt before you start throwing modules at it.
ⓘ Information only. This page provides general educational information about fault code U0422. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does U0422 mean?
U0422 is a Network (CAN bus, module communications) fault code. It indicates: Invalid Data Received From Body Control Module (BCM).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Warning lights on the cluster, often with the check engine light joining in for no obvious reason
- • Interior or exterior lights that flicker, dim on their own, or just stop working
- • Central locking that ignores you, or doors that decide to unlock themselves
- • Power windows, mirrors or sunroof moving erratically or going completely dead
- • Climate control going unresponsive or behaving like it has a mind of its own
- • Occasionally the car drops into limp mode or refuses to start at all
Possible causes
Causes commonly associated with U0422, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Corroded, loose, or chafed wiring and connectors in the BCM circuit or CAN bus harness, by far the most common cause and usually the cheapest to sort
- 2. Weak battery or failing alternator giving the BCM an unstable voltage supply, which on its own makes modules throw invalid data codes
- 3. Poor earth connection at or near the BCM, a classic for intermittent faults that come and go with weather and vibration
- 4. Water intrusion into the BCM enclosure or its connector, common where the module sits low in the car or behind a dash that's had a leak
- 5. Corrupted or out-of-date BCM software, sometimes after a botched or incomplete reprogramming
- 6. A failing BCM itself with internal degradation, less common and worth confirming last
- 7. Aftermarket electronics or dodgy add-ons tapping into the wiring and upsetting the BCM's signals
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Scan every module, not just the engine ECU, and write down anything that comes up alongside it. U0100 and U0140 sitting next to U0422 usually point at a bus or power fault rather than the BCM specifically
- 2. Check the battery at rest (you want above 12.4V) and watch it under load, then confirm the alternator is charging properly. Low or unstable voltage is the cause more often than people expect
- 3. Get eyes and fingers on the BCM connectors and harness. Look for green corrosion, pushed-back pins, water marks, and chafing where the loom rubs against metal
- 4. Clean and check the earth points feeding the BCM. A poor earth gives you exactly this kind of intermittent invalid-data behaviour
- 5. Do continuity checks on the CAN high and low wires between the BCM and the modules complaining about it, looking for breaks or shorts
- 6. If the wiring, earths and voltage all check out, compare the BCM software version against the manufacturer's latest, look for any TSBs, then use bi-directional commands to wake up locks and lights and see how the BCM responds
Common questions about U0422
What can go wrong if I just leave it and keep driving? +
It depends what the BCM is feeding bad data to. The engine and gearbox often carry on fine, so plenty of people drive for weeks like this. The risk is the body electrics. If your headlights, brake lights or central locking start dropping out, that's a safety and security problem, and if the immobiliser data gets confused you can end up stranded when the car won't start. Intermittent faults also tend to get worse, not better, as a corroded connector keeps corroding.
How quickly do I need to get this sorted? +
Soon if any of your lighting, locking or starting is affected, because those are the things that leave you stuck or unsafe. If it's a one-off code with no symptoms you can feel, you've got a bit more breathing room, but get the battery and charging system checked early because a tired battery is a cheap fix that often makes the code disappear. Don't let it run for months hoping it clears itself.
Is it the BCM that's broken, or just the wiring to it? +
Far more often it's the wiring, the connectors, the earths, or the voltage feeding the BCM rather than the module itself. A dead BCM does happen, but it's the expensive answer and it should be the last thing you confirm, not the first thing you assume. Replace one too early and you'll have spent a fair few hundred pounds, possibly into four figures with programming at a main dealer, only to find the same code returns because the real fault was a corroded plug or a flat battery all along.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →