View Full Version : DIY: VTEC System Troubleshoot

05-14-2012, 12:08 PM
So, here is a step by step process of how to diagnose/fix your car if you pull a P1259 - VTEC System Malfunction code in your EP.

What you will need:
Volt Meter that will read Ohms
Fuse Puller
Scan tool (Optional, but preferred)

Step 1: Reset the ECU by pulling the 15A fuse under the hood.
Step 2: Check your oil level, if its below the marked lines on the dipstick, top it up.
Step 3: Start the engine, turn off your A/C and hold it in neutral at 3000RPM until the rad fan comes on (means it has reached operating temp)
Step 4: Do a 1st gear pull that revs over 4000RPM and hold it there for at least 2 seconds. If the code comes up again (either on the Scan tool or the check engine light comes on), do it again 2 more times.

Did the code/check engine light come back on?
Yes - Go to step 5
No - Intermittent failure, so check your oil consumption if you added any before you did Step 3 and check the connections on the terminals on the VTEC solenoid, VTEC oil pressure switch and the ECU

Step 5: Turn the ignition off

Step 6: Disconnect the connector going to the VTEC oil pressure switch
**If you don't know where that is, its labeled N in the picture below**
Step 7: Get our your DVOM and put it to the resistance setting. Check for continuity across the two terminals of the pressure switch
Is there continuity?
Yes Go to step 8. Nothing wrong here.
No Replace the switch (its about $80 from Honda)

Step 8: Turn your ignition to the ON position
Step 9: measure the voltage between the VTEC oil pressure switch Terminal 1 (where the blue and black wire connect) and the body ground.

Is there battery voltage?
YES - Go to step 10
No Check the connection at the ECU
(most likely their will be so I won't go into the whole checking the ECU connection part)

Step 10: Measure the voltage between the two terminals
Is there voltage?
Yes Keep going
No Repair the wire between the switch and the computer (most likely pinched, shorted out or burnt)

Step 12: Turn the ignition off
Step 13: Disconnect the VTEC Solenoid Valve connector
**VTEC Solenoid is labeled as M in picture above**
Check Resistance between the terminals on the solenoid
Is there resistance between 14-18 Ohms?
Yes You should be good, so go back and double check everything you've done so far.
No Replace the solenoid valve

There are other steps to testing the system, but they require specialty tools. All of this information was taken from the Honda EP3 Shop Manual as well.

I had this code come up 3 or 4 times in a week after resetting it constantly and found my issue to be the pressure switch. Great simple way to test your components, save your self some $ from not having a mechanic or Honda diagnose the problem and replacing parts that are still functioning.


05-14-2012, 12:16 PM
nice writeup man :thumbu:

05-14-2012, 11:16 PM
there's one problem with this write-up: