P1259 VTEC Malfunction

Diagnose and fix P1259 VTEC Malfunction

If you have trouble code P1259 VTEC malfunction, here’s a list of things to check to solve the problem.

Understanding the P1259 VTEC malfunction code

Honda uses a variable valve timing mechanism to advance or retard valve timing. The VTEC mechanism is driven by the engine’s oil pressure. The computer determines whether to advance or retard timing and then pulses a solenoid

VTEC solenoid

to regulate oil pressure to the VTEC mechanism. Honda installs a VTEC pressure switch to detect oil gallery pressure and based on that pressure, the computer determines how long to pulse the solenoid on and off. A P1259 VTEC malfunction code will set if the computer doesn’t detect the intended result after commanding a change in valve timing.

Proper oil viscosity is critical to VTEC engines

Honda assumes you’ve used the correct oil viscosity. If you use a heavier or lighter weight oil, it may change the operation of the VTEC mechanism and result in a P1259 trouble code.

Regular oil changes are critical in a VTEC engine

The VTEC phasing device contains a filter screen to prevent sludge and particles from damaging the mechanism. If you go too long between oil changes, sludge builds up and clogs the filter screen. That starves the VTEC mechanism and can cause a P1259 VTEC malfunction code.

High quality oil filters are critical in a VTEC engine

Just like the proper oil viscosity, a VTEC engine requires a high quality oil filter to remove contaminates from the oil. Many rapid type oil change places use the cheapest filters available and those filters may not last longer enough between oil changes, especially if you use synthetic oil and extended oil change intervals.

How to troubleshoot a P1259 VTEC malfunction

Since the computer uses oil pressure derived from the oil pressure switch, it’s always a good idea to read the oil pressure reading on your scan tool before installing a mechanical gauge in place of the oil gallery. If the sensor and gauge readings match, the oil pressure sensor switch is good.

Next, check the VTEC solenoid. Check for good ground and power. Then check solenoid resistance and oil flow. Some shops have found poor grounding prevents the solenoid from opening long enough to ensure proper oil pressure to the VTEC mechanism.

If the solenoid checks out and you have the proper oil pressure at the VTEC mechanism, remove the mechanism and check the filter screen.

Sludge buildup is the most common cause of the P1259 VTEC malfunction code. Check all of the above before replacing the VTEC mechanism

©, 2015 Rick Muscoplat