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P1259 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P1259 is an OBD-II Code that refers to a manufacturer specific code that is defined by the carmaker Honda as VTEC System Circuit Fault (Bank 1)

Meaning

A P1259 code is the indication of a problem, fault, or failure in the electrical control/monitoring system of the VTEC mechanism on Bank 1 caused by a signal from the PCM (Powertrain Control Module) detecting an issue with it. Bank 1 refers to the bank of cylinders that includes cylinder number 1 on V-type engines.

Causes

Common causes for this code include:

  • It's not uncommon for the oil pressure or engine oil level to be low.
  • A faulty VTEC solenoid.
  • Harness connecting the engine to the transmission is open or shortened in the VTEC system.
  • Connections in the VTEC circuit are faulty.
  • The Oil pressure switch is faulty in the engine.

Symptoms

The symptoms of a P1259 code are:

  • A check engine light, Malfunction Indicator Lamp (MIL) will turn on when the car is running.
  • The car may have reduced power in VTEC mode but have normal power in non-VTEC mode.
  • When accelerating in VTEC mode, the lower gears are sluggish and hesitant to downshift.
  • Knocking or rattling noise coming from the top of the engine.
  • Whistling noises are being heard while driving at an idle speed.

It's not uncommon for there to be no visible symptoms except for a P1259 code stored when tested with a scan tool connected via OBD-II port or when moving all electrical components involved with the VTEC system when checking if each one works properly.

Diagnosis

To diagnose a P1259 DTC code, a technician would:

  1. Run a VTEC, Cylinder Balance test on Bank 1 to make sure all of the cylinders are producing power.
  2. Confirm that the solenoid is working properly by checking for 12 volts at its connector when it's activated by turning the ignition switch to ON (RUN).
  3. Verify if there are any oil pressure issues with the engine. If there is no oil pressure or low oil pressure, perform additional diagnostics on the car.
  4. If everything else checks out ok and there is good power production from each bank on V-type engines, inspect and clean up all electrical connections in the circuit. 
  5. Check for shorts in both circuits of VTEC Control Solenoid Valve A and B while listening for any hissing noises when the ignition switch is in ON (RUN) position.
  6. If everything else checks out ok and there are no oil pressure or electrical issues, replace the VTEC solenoid.

Common mistakes

The following are common mistakes when diagnosing the trouble code P1259:

Performing tests when there are no symptoms in the car. A proper diagnosis should have some visible symptoms so that the source of the issue will be easier to identify and fix.

Mistaking this trouble code with Bank 2 or Bank 3 when running VTEC test for Bank 1 when checking where the fault lies within the system.

How serious is this?

A P1259 code is not a serious problem and does not cause any major issues. However, if neglected for too long, these can eventually result in significant damage to other important components.

What repairs can fix the code?

The following are solutions that may fix this problem:

Make sure your car's engine oil is within parameters. Check there are no leaks, which might affect the system's pressure. Make the necessary changes accordingly.

Examine the wires, connectors, and other components of the VTEC system solenoid electrical circuit visually. Make any necessary repairs or adjustments if you find wear and tear or friction damage.

Replace them if you discover any anomalies in these components when performing these inspections.

Related codes

A P1259 is related to and may be accompanied by the following codes:

P0016 – Camshaft Position System Performance (Bank 1)

P0017 – Camshaft Position Sensor Circuit Bank 1 Sensor 1

P0018 - Timing Over-Advanced or Systematic Order (Bank angle)

P1260 – VTEC Solenoid #1 Control Circuit Low Voltage (Bank 2)

P1261 – VTEC Solenoid #1 Control Circuit High Voltage (Bank 2)

P1262 – VTEC Oil Pressure Switch Circuit Low Voltage (Bank 2)

P1263 – VTEC Oil Pressure Switch Circuit High Voltage (Bank 2)

P1340- Knock Sensor 1 Circuits/short to low frequency / open circuit in harness between sensor and ECM.

How much does it cost to fix the P1259 code?

The repair cost of a P1259 code varies depending on the type of repair you want to do. Replacing the VTEC solenoid costs $300-$500, diagnostics cost $100-$200, and labor costs $100-$150. 

What is the estimated cost to fix P1259?

Estimated diagnostic cost = $100 to $200

Estimated part(s) and labor cost = $300 to $500 

Estimated Total Cost for this repair including diagnostics = $400 to $700

Most automotive service professionals can perform this repair with relative ease so the repair price may vary. If you plan on using a mechanic or local garage, there are many factors that will affect the exact price of this type of job such as if they need parts from somewhere else or if any other issues come up while doing the work.

Conclusion

In conclusion, the P1259 code happens when there is a problem with the VTEC solenoid. If you find that your car's engine oil is not within normal parameters, make sure to check for leaks in the system. Wires, connectors, and other electrical components might need checking if they are worn out, damaged, or otherwise compromised. Replacing these components will fix this issue. Make sure to diagnose correctly to avoid future problems with this code down the line.

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