What it means
On engines with multi-profile (cold-start) cam lobes (e.g. some Honda i-VTEC variants and BMW Valvetronic), the cold-start cam profile actuator is not switching as expected — typically a stuck oil control valve or worn locking pin.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Some engines use a separate camshaft profile for cold-start operation, selected by an oil-operated actuator and locking mechanism. The control module compares camshaft behavior with the requested cold-start profile and sets P037C when the system does not switch or perform as expected.
Common causes
Most likely first.
- Cold-start cam profile actuator stuck or failed
- Low, dirty, or incorrect engine oil affecting actuator operation
- Damaged actuator wiring or connector
- Worn or sticking cam-profile locking mechanism
Symptoms
- Check engine light on
- Rough idle or uneven running during cold start
- Reduced power when cold
- Poor cold-start performance
How to diagnose it
- Record freeze-frame data and compare cold-start cam-profile command with available camshaft position or profile status data.
- Check the oil level, condition, and grade against the manufacturer's requirements because the actuator may depend on oil pressure and flow.
- Inspect the cold-start profile actuator connector and wiring for damage, loose pins, or oil contamination.
- Use scan-tool output controls, if supported, to command the profile change and observe whether the reported cam response follows.
- If the command and wiring are sound, test the actuator and inspect the locking mechanism and cam profile components using the manufacturer's procedure.
Common fixes
- Correct low oil level or replace degraded or incorrect oil and filter.
- Repair damaged wiring or clean and secure the actuator connector.
- Replace a sticking or failed cold-start profile actuator or oil control valve.
- Repair worn or sticking cam-profile locking components when inspection confirms mechanical failure.
Can I keep driving?
If the engine runs smoothly once warm and has normal power, a short, gentle drive may be possible, but avoid hard acceleration while cold. Stop driving if it develops persistent rough running, significant power loss, or abnormal engine noise.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.