Variocam actuator trigger voltage?

Anyone knows what the voltage is for the Variocam actuator? I'm getting ~3.3V after 2000rpm. The other pin has a constant battery + (~13.8V) when the engine is running. This is for a '99 C2 (3.4).

The pin that has 3.3v is the "ground" supplied by the DME. When I don't know the exact voltage when variocam is triggered, 3.3v sounds low enough as the solenoid will see 13.8v-3.3v=10.5v across it, which is plenty to actuate it. What problems are you trying to solve?

I have a P1539 code that points to a possible solenoid issue on the passanger bank. I'm trying to check every other possible causes to make sure its not something else like the wiring. How can a "ground" be +3.3V?

The DME uses transistors (not relays) to supply ground which will not be able to pull the voltage all the way to ground. Also, I'm not sure if the DME uses pulses (PWM) to modulate the voltage to the solenoid. I know it does for the timing solenoid in variocam+. For variocam, I think it's a simple on/off. If it does use pulses though, the 3.3v you measured would be an average value of the pulses with some on/off cycle. However, I don't think that's the case. Anyway, what matters is the voltage seen by the actuator. You can measure the voltage between the two pins and it should be ~10.5v based on your previous measurements. You can unplug the solenoid and supply 12v to it when engine is running. Idle should change. Have you tested the other bank? Same voltages?

Fyi https://rennlist.com/forums/996-foru...el-1539-a.html

I had access to a Durametric cable so had the solenoids turned on and off on both banks. The driver side (bank 1).reacted the way it should and the idle sutbked but nothing happend for the passanger side (banks 2). I will measure the voltage between the pins and set something up to ppwer the solenoid remotly to make sure its not working. I'm pretty sure at this point the solenoid is gone but want to be 100% before moving on to pull the valve cover.

Sounds like a good plan. You may also want to ohm out the resistance of the solenoid ~13 Ohm, as mentioned by Logray in post #3 in the link above. If you want to make sure there's enough power reaching the actuator, you can hook up a 12v 6w light bulb (e.g., our peanut size front parking light bulb) in place of the actuator. When rev over 2k or actuated by Durametric, the light bulb should light up. That will tell you the DME is providing enough current and the wiring is good all the way to the solenoid. If the resistance checks out and you can hear a click on the solenoid when powered, maybe the solenoid itself is OK but the actuator is stuck at the idle position. Either case, it needs to be torn down and replacement of both the solenoid and actuator make more sense due to labor. Let us know what you find.

Got tons of those bulbs laying around. Will try that in a couple hours. Getting to the connector was a real PITA, the AC hose and the big coolant hose are in the way. Had to do some creative prying to get the harnes side disconnected. The solenoid side will be a pain to get acess too. I'll try to pull it from below. As usual, I'll report back with everything I find. That's the only way this and other info will ever be usefull in the future.

Some update. Hooked up a 3W peanut bulb to the harness side and it didn't light up. Then I disconnected the bulb and re measured the voltages on the two pins and the B+ was still normal (13.xV) but the other one (I call it trigger pin) now went down from the previous +3.3V to +1.9V. Then checked the trigger pin to see if it was grounding to the chassis and it wasn't. After his I checked for resistance and above 2000rpm the trigger pin goes to ~1600 ohms. This is the same time as when the solenoid is supposed to be triggered. There is something weird going on with the trigger pin (haven't yet checked the solenoid yet). I have also tried turning the peanut bulb on with the trigger wires +1.9V and the bulb did not turn on however at the same time the voltage dropped to pretty much zero (+0.07V) AND the resistance showed an open circuit. I'm starting to think the trigger wire is broken somewhere. In the next few days I'll get the info for the pins at the DME and pinout the harness between the solenoid and the DME.

Imo, slow down a bit First, do NOT measure resistance on the trigger pin unless it's disconnected from the DME! It's connected to the DME directly so you risk damaging the DME by doing resistance measurements, where power is sent from the multimeter to the object being tested. I do not think your trigger wire is broken or shorted. You would have seen no voltage if it was. You are sure the light bulb is not burned? Can you just measure the voltage between the two pins on the harness side? i.e., red probe on one pin and black probe on the other pin (not using the chassis as the ground). If you get 10v or so when the solenoid is supposed to be triggered, the light bulb should turn ON.

I checked that too. Voltage between the two pins is the same as the B+ (~13.4V) all the time, regardless of RPM. The bulb is good, I checked it with the B+ pin and the chassis ground and it lit up nice and bright but when I replaced the chassis ground of the bulb, with the trigger pin, it didn't light up, even above 2000rpm. I will stop the resistance tests.

Um...interesting. I agree that does sound like something funcky going on with the trigger wire. So when the bulb is connected, somehow it doesn't provide a low voltage. I guess next step is to ohm out the solenoid and hotwire 12v to it and see if it works. If it does, that means the problem is only on the DME harness side. Btw, DME 5.2 pin 25 is the trigger wire for bank 2, and pin 52 is for bank 1. Easy to remember with the digits reverse of each other.

Thanks for the info, I'll dig into it tonight.

To hotwire the solenoid, one pin needs to get +12V and the other -12V/ground? I'm planning to use the jumping post in the engine bay for the +12V and the chassis as the ground.

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That should work. One pin to +12v and the other to any ground point or chassis. There's a brass color bolt on the airfilter box close to the latch that provides an excellent ground. Just be careful that the +12v jump terminal in the engine bay is ALWAYS hot, directly connected to the battery +ve terminal and not fused.

The solenoid doesn't need much power. I would bet even a 9v battery can make it click.

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You mean the negative jumper post, with? I�ve been using that all along. Loosed it and squeezed the multimeter probe under it so I wouldn�t have to hold it. The +12V jumper post in the engine bay shouldn't be fused and is always hot, even with the engine off as it is directly connected to the battery. When the battery is dead, this is where the car should be boosted/jumped from. I have a 12V crodless drill, maybe I'lll use it battery it to test the solenoid.

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Yes, yes, and best

Solenoid is good. Has 13 ohms resistance and when triggered with a 12V motorcycle battery, the idle sutbles just likeit did when the other bank was triggered with Durametric the other day. Pulled the DME and someone has been in there before. The cable is wrapped with electrical tape in a sloppy way that it shows someone elses handywork. The DME plug is one piece, unlike in the other write up I saw where there were several smaller plugs connected in a sequence. How are the pins numbered in this one large and long plug?

Found the plug numbering sequence info on the side of the plug.

That's not entirely bad news. Definitely check the resistance between pin 25 and the trigger pin of the bank 2 solenoid connector. The multi-socket DME you saw are for MkII DME 7.8. It has 5 plugs and 134 pins total.

The resistance between pin 25 and the pin at the solenoid is very low (2ohms) the mulitmeter leads alone have about 1.5 ohms so the wiring harness is good. I ran 12V from the motorcycle battery, using the peanut bulb just to see if the wire acts differently when under load and all looked good. The bulb lit up nice and bright. I even moved the DME connector around in case there is a break in the wire when it is twisted and there was no issue with it. The wire for pin 25 is good. This leaves the DME as the problem. A buddy of mine is coming over with a Durametric cable to re check the solenoid end of the connector. If the DME bad, can I splice the 52 pin into the 25 so it will trigger both solenoids? Ofcourse the wire for pin 25 would have to be cut to keep the DME from getting feedback from the jumped line.

You may also want to check the #25 male pin on the DME is not bent and it's mating well with the socket on the DME connector. Next is to open up the DME and check anything obvious on that pin any cold joints on the transistors. I would not recommend tapping into pin 52 to power both solenoids as it may overload the circuit behind. Most likely each bank has it's own indepedent driver. If that circuit is damaged, you will left with no other alternatives but to repair the DME. However, it should not be too difficult to tap pin 52 for its ground signal (negligible current) to trigger an external transistor (MOSFET) to supply ground to the bank 2 solenoid. Or the easy route will be just to send the DME to a specialist for repair.

A fellow RL'er (Gaugeman69) came over to check the DME, we cracked the DME open, followed pin 25 and the diode for it is charred. BINGO! Took some pictures of the diode's numbers, now of to hunt for a replacement diode. I will not use the pin 52 diode to run both banks, instead I'll replace the blown diode. The numbers on the diode are, 30046, 43522.2, 9840. Thanks for all the help, I really do appreciate it a lot. Hopefully this thread will be useful in the future. I'll report back with the results of the diode hunt.

Good job! Must be the fly back diode for the solenoid.

Googled a bit but couldn't find it. Are you sure it's a diode? How many pins it has? Can you post a pic? Like this? image.jpg Fyi https://rennlist.com/forums/boxster-...cu-repair.html

I'm positive its a diode, looks like your pic. I can't post any pics on here anymore or else I would. I did take a picture of it.

Looked at the link and the damage is at the same location except much less severe. Looks like there there is a replacement part number in there too. Thank you!

Those are actually transistors but it doesn't matter Yes, I saw the substitute part number so I posted it here for you. However, if you use that substitute, make sure you read the sub thread that talks about using a mica insulation that may or may not apply to you. I have not read the whole thing. Once it's fixed, you may want to add an inline fuse in series with the solenoid in case the burnt transistor was due to overload from the solenoid. I know you measured the resistance which seems fine but that may change once warmed out. It may have a short that shows up only when hot. So to protect the new transistor, you can use a 2A fuse and drive the car for a month or so to build confidence, then you can get rid of the fuse if preferred. To add the fuse without splicing the wires, you can rig up something with the standard BOSCH Ev1 male and female connectors (i think your solenoid uses these connectors but pls verify) http://forums.audiworld.com/showthread.php?p=14559861 with an inline fuse between the solenoid and the solenoid connector. Completely reversible mod.

Ordered a Bosch PIB373 transiator online. Should be here in a week. Supposed to be a viable replacement for the one that fried in the DME. If it works as it did for others, I'll buy a few more for spare. They are a little over $8each and not too many places sell them. I'll install a fuse inline and keep an eye on it.

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Its a power fet, Not a diode. Imo000 is a traffic engineer...lol.. Yup that one is toast. Bosch must have a hell of an agreement with the auto manufacturers. I can't even find a data sheet for it! Let alone replacement parts. Will have to try Bosch Micro electronics in Michigan. Although the the one he purchased looks like it should work.

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Hehe, I figured. I can't find its specs either. However, I found the spec of BIP373, a triple-stage Darlington for driving ignition coils. Looks very robust, even has overload protection. Should be more than enough to drive that "low current" solenoid (relative to coils). http://www.diyautotune.com/downloads..._datasheet.pdf Good job tracking down the problem btw.

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Yup. If it works (and I am sure it will), It will not fail again. It also has over temp shut off.

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That's where I ordered the part. Getting shipped out today, should be here in a week. My cheapness and not wanting to pull the valve cover what drove me to do a proper diagnosis. I've been like this all my life and seems to work well. Changing a part just to find out that it didn't make a difference feels like a real failure when you are a gearhead.

Part came in earier this week. Gugeman69 changed it for ke. I didn't feel screwing around with it. Re installed it last night, went for a 60 mile emission test run and the check engine light never came back. This morning took it to work, all but the evap systems were ready. One not ready is allowed up here so went to the closest testing facility and as expected it PASSED! The bonus part is that the car feel a bit faster with the variocam working on both banks. I'll be ordering 10 more of these transistors as a back up for the future. Have a feeling that there will be more and more of these faliures as the transiators get older.

Well done!

How hard was to change the transistor ? I have the same issue !

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Not hard at all. I let my buddy do it but only because he had better soldering equipment than me. I was worried that what I had might cause more damage so I let him do it. Once the ECM cover was removed, and the board pulled from the case, it was a very simple procedure. I would contact a local electronic repair shop and have them swap it out. I'm sure they will do it for the cost of couple of rolls of toilet paper.