Troubleshooting P1259 code on a Honda

How to resolving the common P1259 Code on a Honda

The P1259 error code on a Honda is a common issue many Honda owners encounter. This code specifically relates to the VTEC (Variable Valve Timing and Lift Electronic Control) system. When this code appears, it indicates a problem with the VTEC system, which can impact the engine’s performance. Understanding what this code means and how to fix it can save time and money and help ensure your vehicle runs smoothly.

What is the VTEC system?

Honda’s VTEC system is a variable valve timing system that improves the engine’s volumetric efficiency. It uses oil pressure to change valve timing. Where other carmakers change camshaft timing using a solenoid and a phaser with oil chambers, Honda uses two or occasionally three camshaft profiles, and the system hydraulically selects between them.

When the ECM decides to switch cam profiles, a solenoid pulses engine oil pressure to a spool valve that moves a locking pin that connects a high RPM rocker arm to a lower RPM rocker arm. That changes the rockers to a “high lift” profile, opening the valves farther and longer.

The most common causes of a P1259 on a Honda

Since the VTEC system is controlled by oil pressure, the oil condition can play a big role in how the system operates. Low oil or dirty oil can cause this code. So, always start your diagnostic procedure by checking for the proper oil level. Next, check the oil condition. If you routinely run your oil out to the maximum mileage, chances are you’ve developed some sludge issues. In that case, get your oil changed before you do anything else to address this code. If you change out the most commonly failed part, and then run it with dirty oil, you can wind up with the same code. Here are the most common cause of a P1259 on a Honda:

• Low oil level— Check the oil level and top off if needed
• The wrong oil viscosity— The system operates by pulsing engine oil pressure to operate the mechanism. It assumes you’ve used the recommended viscosity oil. Using a different viscosity can throw off the amount of oil that gets pulsed when the VTEC solenoid operates. Never fill your engine with a different viscosity
• Low oil pressure— If your oil light is on in addition to the check engine light, resolve the low oil pressure issue first.
• Dirty oil/sludged oil— Change the oil and filter before addressing the code
• Faulty oil pressure sensor— Replace the sensor
• Faulty VTEC solenoid— Replace the solenoid
• Faulty VTEC wiring at the sensor or solenoid— Using a multimeter, check for the expected voltage and good ground

Fixing the P1259 code on a Honda

Start with an oil change

You don’t want dirty oil getting pushed into new parts. Trust me on this. Starting with clean oil can eliminate many problems.

Replace the oil pressure sensor/switch

Aside from low oil, the wrong viscosity oil, or dirty oil, the single most common cause of this code is a faulty oil pressure sensor switch. Over time, the diaphragm in the switch can fail, causing the code to set.

The Honda oil pressure sensor looks like a normal engine oil pressure switch used to operate an oil pressure gauge on your dash or report engine oil pressure to the ECM. This one, however, is dedicated to the oil gallery that runs the VTEC system. The sensor screws into the cylinder head and is easy to remove. But I have to caution you about the installation. The sensor

This is a typical Honda VTEC oil pressure switch

has a tapered thread. You’ll want to tighten it enough to prevent leaking, but avoid over-tightening because that can crack the cylinder head threads, and that’s a major repair cost.

Consult an online Honda OE parts diagram to find the right one for your year, make, model, and engine. I highly recommend buying an OE part. The aftermarket parts are cheaper for a reason. Even if the aftermarket parts have a lifetime warranty, do you want to be dealing with this issue again? Because, in my experience, the aftermarket parts usually fail within a year or two.

Replace the VTEC solenoid if the P1259 is still there

If you’ve replaced the oil pressure sensor/switch,

Typical Honda VTEC solenoid

confirm the correct oil level and cleanliness and that the electrical connectors to the sensor and solenoid are within spec. It’s time to replace the solenoid.

As with the sensor, I recommend using a genuine Honda OE part for this repair. Refer to a shop manual for the solenoid’s location and torque specs. Then, remove and replace it.

Prevent the P1259 code from reoccurring

• Regular oil changes— Use the recommended viscosity oil and the most current oil rating SP and GF-6. Keeping the oil changed on time and clean, goes a long way to preventing clogging in the filter screen located in the VTEC solenoid.

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

©, 2015 Rick Muscoplat