Low engine oil level or oil in poor condition, degraded or wrong grade; Blocked VTEC solenoid filter screen or restricted oil passage to the VTEC solenoid; Faulty VTEC solenoid valve (stuck or electrically failed); Faulty VTEC oil pressure switch or its signal; Damaged wiring, poor connector contact or corrosion in the solenoid or pressure switch circuit; Oil leak at the solenoid gasket or seal causing a loss of VTEC oil pressure; Internal valvetrain fault such as a worn or stuck rocker arm or VTEC piston, or a control unit fault.

P1259

VTEC System Malfunction Rear Bank 1.

Honda
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
2: AreaFuel and air metering (injector circuit)
59: FaultThe specific fault in that area

What it means

P1259 on a Honda means the engine control unit has detected a fault in the VTEC (variable valve timing and lift) system on the rear bank of the engine. It typically sets when the VTEC oil pressure switch signal does not match what the control unit expects when the VTEC solenoid is commanded on or off. This usually points to low or poor oil supply, a solenoid or pressure switch fault, or a wiring problem. Affected engines and bank layouts vary by model, so check the correct procedure for the specific vehicle.

Symptoms

Check engine light on
Loss of top-end power or the engine feeling flat at higher revs
VTEC not engaging, or a noticeable lack of the usual change in engine note
Rough running or hesitation around the VTEC changeover point
Slightly poorer fuel economy
Possible reduced performance if the control unit limits operation

Possible causes

Low engine oil level or oil in poor condition, degraded or wrong gradelikely
Blocked VTEC solenoid filter screen or restricted oil passage to the VTEC solenoidlikely
Faulty VTEC solenoid valve (stuck or electrically failed)likely
Faulty VTEC oil pressure switch or its signalpossible
Damaged wiring, poor connector contact or corrosion in the solenoid or pressure switch circuitpossible
Oil leak at the solenoid gasket or seal causing a loss of VTEC oil pressurepossible
Internal valvetrain fault such as a worn or stuck rocker arm or VTEC piston, or a control unit faultrare

How to diagnose

Read the stored codes and freeze frame data, noting engine temperature, load and rpm when the fault set, and check for any other codes
Check the engine oil level and condition, and confirm the correct grade is fitted for that engine
Inspect the VTEC solenoid and pressure switch connectors and wiring on the rear bank for damage, oil contamination, chafing or corrosion
Check around the VTEC solenoid for oil leaks
Test the solenoid coil resistance and its power and ground feeds against the manufacturer specification for the engine
Test the VTEC oil pressure switch operation and its signal to the control unit against the specification
Remove the solenoid and inspect and clean its filter screen, then check the oil passages are clear
If all is in order, check oil pressure and inspect the valvetrain, following the model-specific procedure

How to fix

Correct the oil level and change the oil and filter with the correct specification oil if it is low or degraded
Clean or replace the VTEC solenoid filter screen and clear any blocked oil passage
Replace the VTEC solenoid and its gasket or seal if it has failed or is leaking
Replace the VTEC oil pressure switch if it is faulty
Repair or replace damaged wiring and connectors in the affected circuit
Repair any internal valvetrain fault found, following the model-specific procedure

Can I keep driving?

Medium severity

The car can usually be driven short-term with VTEC not working, but avoid hard driving and high revs. Check the oil level first and get it diagnosed soon, as low oil pressure can cause engine damage.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.