Vvt valve no power

AndyGman · May 21, 2026, 11:19

First of hello to you all new member here I have a 2002 roadster that I absolutely love but have run into a problem I recently received a P1656 fault code VVT-i Oil Control Valve so replaced this part but I am still getting the same problems of poor running and no power over the past 2 weeks I have done the following

New maf sensor
New vvt valve
Tested the following parts and all readings were good including bench tests Fuel evap, throttle position sensor, Air intake temp sensor, and finally the new vvt valve now here is where my journey begins I tested for voltage from the vvt harness and only get 2.5v when ignition is on and no movement when car is started I have traced the harness back to the ECU and there is continuity to the ECU pins which makes sense if it is getting some voltage I'm now at a loss and would love any help or suggestions thank you

Ardent · May 21, 2026, 12:46

We do like to assist with problems.

And we always start at the simple (cheap) end. For all the testing you have done, and suggests you know your stuff.

Have you checked the very basics. Condition of air filter? Plugs.

If running but struggles with power, can indicate a blocked cat, but let's work up to that.

AndyGman · May 21, 2026, 16:03

Yes I'm going to check the pre cats over the next few days well from the 02 sensors hole just car was running mint till P1656 and the code won't clear and the voltage problem but thanks it's my first call

bobo83 · May 21, 2026, 17:39

Have you tried starting the car with the solenoid plug disconnected ? If the symptoms are the same, then the ECU is not happy about the VVTi solenoid.

Continuity on the cables is a positive sign. The cables might be damaged though and short with some other signal ? Continuity won't detect that.
Also, I believe the signal is PWM and not constant voltage, a multimeter won't measure that very well (unless you have Hz / duty cycle mode).

The workshop manual covers this error code, and it lists 3 trouble areas:

Open or short in OCV circuit
OCV valve
ECM

If everything else fails, the ECU must be the problem.

Carolyn · May 21, 2026, 23:07

Have you cleaned the little filter just below the valve on the head?

If it's clogged the valve might shuttle but no oil (or not enough) will get through to operate the VVT hub.

It's a pig to get out - best to remove the solenoid valve first. Loosen the oil dip tube from the head and gently move it out of the way. The filter sits behind the bolt head below the tube.

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AndyGman · May 22, 2026, 11:49

Ok thanks for all the suggestions I have checked the pre cats and look good from the 02 sensor holes I have also cleaned the little pain in the neck filter it wasn't to bad cleaned it up but all the same also bench tested the solenoid all ok also tested for shorts didn't find any started the car up with the solenoid unplugged still runs the exact same and still only 2.5v from the harness also to add when I unplug the MAF sensor the car runs great till 3000 revs then goes into limp mode. I'm at a total loss oh I also tested spark plugs and coils all good

Carolyn · May 22, 2026, 14:20

I belive the VVT system responds to rpm and load. So . perhaps the crank sensor is not giving the right signal? Often it is the ground connection. At the bottom of the tiiming cover.

Just a possiblity.

AndyGman · May 22, 2026, 16:04

Thanks I will check it out

AndyGman · May 22, 2026, 18:47

Begining to think ECM as that's what sends the signal crank sensor all good only code Is P1656 that won't clear

AndyGman · May 22, 2026, 18:48

Also checked live data for a few reading and all seem ok

Carolyn · May 23, 2026, 08:26

I'm not saying it's not down to a faulty ECU. The only way to find out is to install another one. You'll need the key that goes with it.

It's also possible that the VVT hub is not performing as it should... That would still, probably, manifest as a poorly functioning OCV.

Have you checked the cam position sensor? It also could have a bad earth.

shnazzle · May 23, 2026, 10:04

If you have an OBD2 dongle, I may still have an APK of a Toyota-specific android app that allows you to activate the VVT valve manually degree by degree.

Ardent · May 23, 2026, 10:52

AndyGman · May 23, 2026, 12:12

Thanks again I will try the camshaft sensor Carolyn thanks for the info how can I test the vvt hub is this possible like I said it's the voltage that's got me wondering if I set 12v into the solenoid the car shuts down.
I do have a dongle Shnazzle that would be a great apk to test it I guess I will pm you thanks

Carolyn · May 23, 2026, 12:58

Basically, you have to remove the camshaft to test the hub. Then use compressed air in one of the oil holes in the camshaft to see if it unlocks and moves relative to the camshaft.

They can fail - it's not a common fault but is does happen.

shnazzle · May 23, 2026, 13:57

Quote from: AndyGman on May 23, 2026, 12:12Thanks again I will try the camshaft sensor Carolyn thanks for the info how can I test the vvt hub is this possible like I said it's the voltage that's got me wondering if I set 12v into the solenoid the car shuts down.
I do have a dongle Shnazzle that would be a great apk to test it I guess I will pm you thanks

I managed to install it from my history on play store, but it's no longer there. A ehile back I'm sure I managed to make a hard backup of my phone but I can't find it.
A google pointed me to this: https://apkpure.net/elmscan-toyota/com.elmscansoft.toyota?

AndyGman · June 1, 2026, 16:29

Sorry for not replying I have been on holiday yee ha so I have tested the camshaft and crankshaft sensors all readings are good so now I wo t be testing the vvt hub as well to be honest I can't be bothered so I'm thinking of taking a punt on the ECM and key change as the voltage coming from the ECM to vvt valve stays at 2.5 v no matter what unless anyone can suggest a better fix I'm really glad and happy for all the replies I have had it has helped me no end but like I say the hub is a bit of a pain to do especially on the drive so the £50 punt seems my best option then after I change if it's the same I would be thinking vvti hub what does everyone think thanks Andy

Carolyn · June 1, 2026, 17:37

Changing the hub isn't that bad of a job. Shnazzle and I did all his valve buckets in a hotel car park!

AndyGman · June 2, 2026, 12:36

Ardent · June 2, 2026, 20:38

True story.

That's the way we roll.

Joesson · June 3, 2026, 08:42

Not to mention the Member that changed his dampers in the car park on Ding Day!

AndyGman · June 7, 2026, 13:59

Ok now I'm going crazy I tested the MAF the new one with live data and it's just under 2 gas when I accelerate it just dies so no reading I plugged in the old MAF the vvti valve code went away but at idle I get 2-4 has and when I accelerate to 2500rpm it rise to
7-10 gas but it does accelerate but under load there is no power at the wheels when revving the old one it does bounce about I also read the air intake temp sits about 29 degree and I realise the new MAF is Chineseium reckon it never worked also voltage and signal read messed up with the new one but read good in the old one so I reckon the old one is still busted not correct readings and the new one is just FUBAR reading do we think it's worth changing for a nice one thoughts please 🙏

Carolyn · June 7, 2026, 17:15

Yes - cheap MAFs are like cheap paint!!

Get a Denso and have done with it. Same goes for O2 sensors.