I replaced the head gasket and timing belt on my 2002 Honda Accord 2.3 EX a couple of months ago. Since, I am getting a chronic P1259 VTEC code. I've replaced the oil pressure switch and verified that the solenoid triggers at 12v using a Power Probe. I've disassembled the spool assembly and verified there is no gunk build-up on the screen and I've lubed it all up using Marvel and confirmed all moving parts operate smoothly before re-assembly. I've torn down the engine again and confirmed my timing is dead on.

The only issue I can concretely find is that I am only getting 10v from the 2P connector on the oil pressure switch. From the troubleshooting videos I've found, this should be 12v. I've moved wires around using "wiggle" tests, and I cannot get any voltage fluctuations. As far as I can tell this voltage comes directly from the ECM. What am I missing? What is telling the ECM what voltage to supply? I don't want to go directly to replacing the ECM unless I absolutely have to.

Thank You for any help you can supply!

 

Verify your engine bonding jumper, harness ground, body ground, and main ground on the battery are all clean and tight. Resistance will reduce overall voltage.
What is your battery voltage, KOEO and KOER.
If the voltage of the battery is really low then the multiplier in the PCM may not be sending the correct voltage.
Those 98-02s can run off some fairly dead batteries. Neighbor was running around with a car that barely put out 9V. I was pretty amazed.

 

Hey, I'm still working on this! (lol) I've pulled the lower end to make sure I wasn't getting any gumming from where the antifreeze mixed with the oil previously. So, I've got the top end and lower end off of the block.

I'm sorry - what's an "engine bonding jumper" and where do I locate this? I've inspected all of the grounds I can see visually - I'm not sure how any would have changed from before I did the head gasket job. I'm getting 14.2v running and 12.1 standing at the battery.

After sitting a bit, I noticed the voltage at my solenoid dropped from 10.2 to 9.8v. Cannot figure this out to save my life.

So, this is my first Honda job, so working on it is a bit foreign to me. When I removed the head I decided to pull it along with the manifold as it seemed much easier. When pulling I snagged a couple of wires that were under the intake that I could not see on my first inspections. This broke the knock sensor and surely yanked on whatever that other oil pressure sensor is next to the knock sensor. I had to replace the knock sensor, but I am unsure about any damage to these wires. However, I am not getting corresponding codes now and I was previously.

I cannot find a good diagram of the ground locations, but I do not think this is the culprit - unless I reconnected a ground lead to a mount point that it was not on previously! But, I have no reference.

Again, any help that I can get will be greatly appreciated. I feel like I"m losing my mind at this point.