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Error Code P1259 is defined as VTEC System Malfunction.
This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Honda, Acura, etc. Specification of the definition, troubleshooting, and repairs still vary from one make and model to another.
The VTEC system or Variable Valve Timing and Lift Electronic Control system, activates the VTEC solenoid valve through the command sent by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes). It charges and discharges the hydraulic circuit of the VTEC mechanism installed in the valve system to switch the valve timing between low and high. The PCM then monitors the oil pressure conditions in the hydraulic circuit of the VTEC mechanism, which depends on the VTEC oil pressure switch downstream of the VTEC solenoid valve. The PCM will oversee the system and should there be any disparity between the oil pressure condition in the hydraulic circuit determined by the PCM command, and the oil pressure determined by the status of the VTEC oil pressure switch, then this system will be read as a fault, setting the code P1259.
Error Code P1259 is detected when there is a problem in the VTEC oil pressure switch or at the VTEC solenoid valve circuit.
As with other error codes, Error Code P1259 activates the Check Engine light and registers the code to the vehicle’s memory system. Other than that, there are usually no drivability issues and concerns that go along with this error code.
This error code can be caused by multiple of factors, such as:
- Low oil pressure or low engine oil level
- Defective VTEC solenoid
- Open or shorted VTEC harness
- Poor electrical connections in the VTEC circuit
- Defective VTEC oil pressure switch
How to Check
This error code can set at idle or above 4,000 RPM. When set at idle, the problem will be in the VTEC pressure switch (switch, connectors, or wirings). If the code is set at 4,000 RPM on the other hand, then the problem is low oil pressure in the VTEC system
To find the right cause of the error code, do the following:
1st Step: Use the PGM tested to check the freeze data of the vehicle, or snapshot data to determine when the code was set. If set at idle, then proceed to 2nd step.
If set above 4,000 RPM, then proceed to 4th step.
2nd Step: Disconnect the 2P VTEC pressure switch connector and then jump its two wires.
3rd Step: With the ignition switch On (II), the PGM tester must show that the VTEC pressure switch is On. If the tester says the switch is On, the wiring and connectors are ok. Thus, the switch must be bad. If it’s bad, then it must be replaced before clearing the codes.
If the switch is Off, check for open circuit between the switch and the PCM or between the ground and the switch. After repairing the open circuit, check the switch again before clearing the code.
4th Step: Take off the valve cover, and then check for any loose center head bolt on the side of the intake manifold. A loose bolt can easily cause a drop in the VTEC system’s pressure.
If there are no loose bolts, then proceed to 5th step. If the bolts are loose on the other hand, then tighten it with 22 lb-ft torque (29 N.m.). Turn it with another ¼ turn, and then turn for another ¼. If you can’t seem to tighten the bolt, then there’s a problem with the thread of the bolt.
5th Step: Take off the VTEC rocker arms and then check them for sticking or missing synchronizer pistons, or other valve train problems that could cause oil leaks.
If there are any piston or valve train problems, then you must replace the defective parts before clearing the codes.
How to Fix
The most common cause for Error Code P1259 or VTEC system malfunction is low oil pressure. Thus, make sure you check your oil if it’s due for service. Change oil and filter if necessary. Clear the codes and then give it a try.
The next cause would be the VTEC oil pressure switch, located right above the oil filter. If it’s in bad condition, then replace it with real original Honda oil pressure switch.
Lastly, you could have a restricted VTEC solenoid passage, or faulty VTEC solenoid or wiring. Repair or replace as needed.
For oil pressure test, you will need an oil pressure gauge. Most often than not, the problem with the solenoid is mechanical, not electrical. Dirty or contaminated oil can cause the solenoid to get stuck.