What does it mean?
P1257 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: VTEC System Malfunction . 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
- The MIL is on and the engine will not pull past mid range
- Clear loss of top end power while low speed driving feels normal
- No change in engine note where the high lift profile should engage
- Slightly increased fuel consumption
- Occasionally a light ticking from the top of the engine
- Fault often returns after an oil service done with the wrong grade
Likely causes
- Low engine oil level or oil that is old, thin or heavily contaminated
- Blocked filter screen in front of the VTEC solenoid restricting oil flow
- Spool valve inside the solenoid sticking with varnish or debris
- Faulty oil pressure switch that reports the wrong feedback to the module
- Weak oil pump or excessive engine wear giving low pressure at the switching point
- Wiring or connector fault on the solenoid or pressure switch circuit
- Seized locking pins in the rocker assembly on a high mileage engine
How to fix it
- Check oil level and condition first and confirm the correct grade and a recent filter change
- Command the system on with the scan tool at raised rpm and watch the oil pressure switch state change
- If the switch state does not change as commanded, test the switch and its wiring before the solenoid
- Remove the solenoid, clean or renew the filter screen and inspect the spool for varnish and free movement
- Measure the solenoid resistance and check its supply and ground with the circuit commanded on
- Check actual oil pressure with a mechanical gauge at the specified engine speed if the hydraulic side is suspected
- Renew the solenoid, screen or pressure switch as proven, refill with the specified oil and verify the system now switches on live data