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Afternoon folks,
Before I condemn my 06 Civic Vtech oil pressure sensor I was wondering if someone can give me a known good measurement? I’m looking at the Vtech rocker arm oil control valve. Car sets the P2647 code immediately after key on (KOEO).
At rest, my Civic 1.8L has 5V on the yellow/black wire and 4.7V on the black/white. Green is ground. See attached wiring diagram.
I know it’s a big favor!
So I’ve done a bit more research and this engine is interesting. Beginning with the 06′ Civic 1.8 I-Vtech Honda took a completely different approach to the Vtec system.
My car’s engine is running on the “hot cams” most of the time. It is only when you get out on the highway and hit cruising speeds that the rocker arm oil control valve is energized and the “economy lobes” of the cam are engaged. This is completely opposite to the designs of the past. I had no idea.
I guess my car is thinking (via the oil pressure sensor) that the economy lobes of the cam are engaged at all times rather than the traditional Vtec hot cams. I suppose this is why my car has an oil pressure sensor rather than a switch because of the various criteria that have to be met in order to engage the economy mode.
At startup, the economy mode of the cams is not supposed to be engaged (Vtech solenoid off). I believe my car somehow believes that oil pressure is present (faulty sensor, or wiring) and I’m getting the code. I would very much like to know if the oil pressure sensor operates like a potentiometer or maybe it generates a square wave and the ECU interprets the frequency. I guess I could test but it would be nice to have a scope!
So I’ve done a bit more research and this engine is interesting. Beginning with the 06′ Civic 1.8 I-Vtech Honda took a completely different approach to the Vtec system.
My car’s engine is running on the “hot cams” most of the time. It is only when you get out on the highway and hit cruising speeds that the rocker arm oil control valve is energized and the “economy lobes” of the cam are engaged. This is completely opposite to the designs of the past. I had no idea.
I guess my car is thinking (via the oil pressure sensor) that the economy lobes of the cam are engaged at all times rather than the traditional Vtec hot cams. I suppose this is why my car has an oil pressure sensor rather than a switch because of the various criteria that have to be met in order to engage the economy mode.
At startup, the economy mode of the cams is not supposed to be engaged (Vtech solenoid off). I believe my car somehow believes that oil pressure is present (faulty sensor, or wiring) and I’m getting the code. I would very much like to know if the oil pressure sensor operates like a potentiometer or maybe it generates a square wave and the ECU interprets the frequency. I guess I could test but it would be nice to have a scope!
Hi Eric, thanks for the info….
I was out working at it today and unfortunately, I didn’t get anything definitive. I took the engine oil pressure sensor out and gave it a good cleaning. I re-installed, cleared the code and got the same code right away. I didn’t even start the car and the code popped up again.
So…thinking about the code description “rocker arm actuator stuck on”. How could the VTech actuating system be stuck on with no oil pressure? Don’t forget, the car’s not running and it’s setting the code again. Seems to me that the oil pressure sensor is “sensing” oil pressure even when the engine is off. Any residual pressure would have been relieved when I removed the sensor. Kinda makes you think it’s the sensor at fault. Of course, I could be wrong because maybe the ECU isn’t forgetting the code or something screwy like that.
I also disconnected the Vtech solenoid and manually energized it…..big solid clicks. That’s a good sign I suppose!
I called Honda and the engine oil pressure sensor is 170 bucks. The parts guy alerted me to the fact that the whole solenoid valve (oil press sensor, gasket and new filter included) is 170 bucks……might as well replace the whole thing.
Still though, I wish there was some way to figure out how that sensor works. I would love some proof before I blow 200 bucks.
By the way….if anyone runs into this and has to take that Vtech oil pressure sensor out, a 1-1/8″ deep socket will do it. Not sure what the Metric equivalent is and no doubt 1-1/8″ is not the correct one but it fits pretty snug. Lucky I had one from my days of working on aircraft. I had nothing near it in metric. Probably a 28mm or something.
Hi Eric, thanks for the info….
I was out working at it today and unfortunately, I didn’t get anything definitive. I took the engine oil pressure sensor out and gave it a good cleaning. I re-installed, cleared the code and got the same code right away. I didn’t even start the car and the code popped up again.
So…thinking about the code description “rocker arm actuator stuck on”. How could the VTech actuating system be stuck on with no oil pressure? Don’t forget, the car’s not running and it’s setting the code again. Seems to me that the oil pressure sensor is “sensing” oil pressure even when the engine is off. Any residual pressure would have been relieved when I removed the sensor. Kinda makes you think it’s the sensor at fault. Of course, I could be wrong because maybe the ECU isn’t forgetting the code or something screwy like that.
I also disconnected the Vtech solenoid and manually energized it…..big solid clicks. That’s a good sign I suppose!
I called Honda and the engine oil pressure sensor is 170 bucks. The parts guy alerted me to the fact that the whole solenoid valve (oil press sensor, gasket and new filter included) is 170 bucks……might as well replace the whole thing.
Still though, I wish there was some way to figure out how that sensor works. I would love some proof before I blow 200 bucks.
By the way….if anyone runs into this and has to take that Vtech oil pressure sensor out, a 1-1/8″ deep socket will do it. Not sure what the Metric equivalent is and no doubt 1-1/8″ is not the correct one but it fits pretty snug. Lucky I had one from my days of working on aircraft. I had nothing near it in metric. Probably a 28mm or something.
Well it appears my wiring diagram is wrong…..found this one this morning. It’s not a oil pressure switch, it’s a sensor. Appears to have a reference voltage. Not quite sure how to test this one.
Well it appears my wiring diagram is wrong…..found this one this morning. It’s not a oil pressure switch, it’s a sensor. Appears to have a reference voltage. Not quite sure how to test this one.
Well I had a quick look this afternoon and I found a couple strange things….
First, my wiring diagram has two wires on the VTech oil pressure switch. When I looked at mine, I saw three. Yelow/red, black, and what appeared to be a green. I have no idea why there are three wires on this thing.
The other strange thing I noticed was on the VTech solenoid. I checked for voltage on the blk/wht wire with the key off and on….on both occasions, there was a steady 3.5 volts. Seems to me there should be none.
Well I had a quick look this afternoon and I found a couple strange things….
First, my wiring diagram has two wires on the VTech oil pressure switch. When I looked at mine, I saw three. Yelow/red, black, and what appeared to be a green. I have no idea why there are three wires on this thing.
The other strange thing I noticed was on the VTech solenoid. I checked for voltage on the blk/wht wire with the key off and on….on both occasions, there was a steady 3.5 volts. Seems to me there should be none.
So from reading about the V-tech system and watching some helpful Youtube clips the way I’m understanding this is:
At high RPM’s the ECM is supposed to command the Vtech system to engage. Power is sent to the rocker arm oil control valve solenoid which sends oil under pressure to the pins in the valve train, locking them together and changing the cam profile.
The oil pressure which is now present in the rocker arm oil control valve actuates the oil pressure switch (telling the ECM that the VTECH hydraulic actuating system is working correctly). The switch is normally closed to ground and the presence of oil pressure opens the switch. The ECM “sees” voltage (12V) rather than being connected to ground (0V) and all is well.
My car is throwing the P2647 VTEC Oil Pressure Switch Circuit High Voltage code at startup. If I clear the code, it returns immediately after start up. So, without doing any testing I’m thinking that at startup, the ECM should be seeing 0V at the oil pressure switch. The fact that it says high voltage makes me think that the switch is open……it should be closed at idle with no Vtech engaged. The ECM sees 12V when it is expecting 0V and throws the code.
Now, I’m assuming a little here but I want to think i’m on the right track and have a place to start. I’m thinking remove the oil pressure switch and clean it. I guess, conversely, the rocker arm control valve could be stuck on too at low RPMS…..therefore, oil pressure would be present at the switch. Would cause the same symptoms I believe.
There’s lots of voltage testing that can be done here so I will update with what I find. Damn thing is in a pretty crappy location though!
So from reading about the V-tech system and watching some helpful Youtube clips the way I’m understanding this is:
At high RPM’s the ECM is supposed to command the Vtech system to engage. Power is sent to the rocker arm oil control valve solenoid which sends oil under pressure to the pins in the valve train, locking them together and changing the cam profile.
The oil pressure which is now present in the rocker arm oil control valve actuates the oil pressure switch (telling the ECM that the VTECH hydraulic actuating system is working correctly). The switch is normally closed to ground and the presence of oil pressure opens the switch. The ECM “sees” voltage (12V) rather than being connected to ground (0V) and all is well.
My car is throwing the P2647 VTEC Oil Pressure Switch Circuit High Voltage code at startup. If I clear the code, it returns immediately after start up. So, without doing any testing I’m thinking that at startup, the ECM should be seeing 0V at the oil pressure switch. The fact that it says high voltage makes me think that the switch is open……it should be closed at idle with no Vtech engaged. The ECM sees 12V when it is expecting 0V and throws the code.
Now, I’m assuming a little here but I want to think i’m on the right track and have a place to start. I’m thinking remove the oil pressure switch and clean it. I guess, conversely, the rocker arm control valve could be stuck on too at low RPMS…..therefore, oil pressure would be present at the switch. Would cause the same symptoms I believe.
There’s lots of voltage testing that can be done here so I will update with what I find. Damn thing is in a pretty crappy location though!
So lets assume you cannot budge bleeder screw after all that work….lets go worst case scenario (short of a snapped off bleeder).
So lets assume you cannot budge bleeder screw after all that work….lets go worst case scenario (short of a snapped off bleeder).
So lets say you’re changing your brake pads and you have to push the piston back. You go to crack the bleeder and you find it seized. How, generally, would you proceed? I’m assuming heat is a last option?
