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YOUR RESEARCHConfirming Variocam transistor
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Check connections going back
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So, I replaced the connection for the bank 1 solenoid and checked all the connections going back to the DME.
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So, I replaced the connection for the bank 1 solenoid and checked all the connections going back to the DME.
Replace while doing the solenoid replacement at the same time
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My car was out of spec and I had to have the tensioner pads replaced while doing the solenoid replacement at the same time.
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As soon as I reset the code, it comes back within a mile of driving.
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Suggestion
I would fine a good shop to take your car to and make sure they diag your car properly and systematically and if they find a bad solenoid and they check the tensioner pads, they will hopefully only replace what's needed and not perform any guesswork repairs.
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First, when this first happened to me, I found a thread in the Boxster section where someone drove the heck out of the car and the problem went away.
1999 911 C2 Cab - I have been researching a P1531- the engine changes it's sound when I apply a 9v battery to the Variocam solenoid, so I opened the ECU and found a burnt transistor- but it's on the outside row of transistors and I haven't seen that in images yet.
That's pretty cool. I don't know what you mean by "I haven't seen that in images yet"....but I would not be surprised if you found your issue.
I did look up the transistor number on ebay and found two hits. I don't know what the second two lines are.
https://www.ebay.com/itm/12331517862...Bk9SR6TlpoCnYw
https://www.ebay.com/itm/25320492557...Bk9SR6TlpoCnYw
The images I have seen for burnt transistors are normally on the inside of that heatsink. This one being on the outside makes me wonder if it's not the bank1 variocam solenoid signal. I ordered the transistor specified in other threads, $20 shipped but hopefully here quick as the sender is a hour from me. I was not able to test voltage at the solenoid as the connector is too short to get leads into from the wheel housing. But if the Durametric trigger doesn't work and a 9V battery does, it must be the ECU or the wire from ECU to the solenoid. Maybe 1999 ECUs were different than the other threads.
I may have found my own answer, the photos I have seen appear to be for bank2, and I am chasing bank1- I will trace the transistors to the pins and reference a pinout - pin
52 - Camshaft adjustment, bank 1, pin 25 - Camshaft adjustment, bank 2
I think your testing method is flawed and inconclusive, but your visual inspection of the DME confirms a bad transistor...( probably from a shorted vario-cam solenoid on bank 1 or bank 2).
Both solenoids share a common 12v power lead, but have separate ground (-) leads to bank 1 and bank 2 solenoids and individual testing is necessary to determine which one is/was shorted..( caution: it can be an intermittent short and not show up at certain temps)
I did see solenoid continuity and resistance of 16.5ohms, trying to find out if that is out of spec range (I found nominal is 13.5). If that is out of spec, I don't want to fry the new transistor as well, please let me know a better way to determine a shorted solenoid.
The nominal spec is 13 ohms ( less than 1 amp) and your reading of 16.5 ohms is even less amps ( and will not blow a transistor ) but you probably have an intermittent short occurring only at engine temps of ~ 200F.....You could perform the test again and heat the solenoids slowly to 250F ( with a heat gun) and watch the ohms reading to see if the short occurs ( like down to 1-5 ohms) when the temps are high..
Or as an alternative, you could install 2 2amp fuses in-line on the ground leads of each solenoid to protect the DME and also show you the faulty solenoid ..( when the fuse blows)...
I went through a P1531 code, failed solenoid, and then a failed/burned DME as well. That transistor failure came with a 2nd solenoid failure on the other side (P1530).
I agree that the problem with the shorts is:
1) The shared ground
2) An intermittent failure
I ended up having ECU doctors fix the 5.2 Motronic ECU (I have a 99 also), and had a shop replace the failed solenoids. They also replaced the tensioner pads, top and bottom, both sides, as I had brown debris in the oil filter and my cam deviations were -4 and -2.
That was maybe 3-4 years ago, and the car has been great ever since.
EDIT: pic of my failed transistor
I have installed the transistor and 2A ground fuses in the brown wire at the solenoid, bank1 now actuates through Durametric and the 1531 has not come back on some good drives, thanks everyone! I will update when the fuse blows and the code comes back.
Yup, soldered in the new transistor and have now gone ~20 miles without incident. The car doesn't seem any different with Vario working again. Not sure what I expected, I bought it with this issue
Interesting. My guess is that the Variocam being suck open/on behaves differently than stuck closed/off. And having one side working while the other side is not makes a difference as well.
Hi Everyone,
I'm a new owner of a 1998 Boxster 986. The car has 38K miles on it, and I have code P1531 on the solenoid bank 1. I applied a 9V battery to the connector and heard a click. I'm unsure if it's the solenoid or the wiring short issues. Any advice on tackling this problem would be greatly appreciated.
Per Porschetech3�s post earlier, check each solenoid separately. You could take also take apart the DME and check for obvious signs of a burnt transistor.
I'm reading through all the posts. Definitely great information. Additionally, I just got the values on the cam positions:
Cam position 1 deviation -2
Cam Position 2 Deviation -9
At idil, is this normal?
Also, I got the .04 oms while the car was off. Am I supposed to do this testing while the car is started? Also, what about if the car is running, and I unplug the solenoid connector and if the engine sound changes.. is that another way to test it or will I harm the engine at that point?
Generally, anything 6 or above difference between the two indicates too much difference, and you are at 7. My car was out of spec and I had to have the tensioner pads replaced while doing the solenoid replacement at the same time.
Have you inspected the oil filter recently? If the pads are wearing, you might find little brown bits of plastic in the oil filter.
There are two chain pads, top and bottom, on each side of the engine for a total of 4. There is also an IMS tensioner pad, but that is not replaceable without splitting the engine case.
I just recently purchased the car, and during the 1st oil change, it was clear. The car sat between the previous owners a lot and barely driven. It has 38K miles on it. Could the bank 1 solenoid failure cause this higher rating of 7? The car runs strong for sure. The engine steadily idles at 750-800 RPM.
If the tensioner is stuck on when it should be off or vice versa, the cam deviation numbers would be way higher - double digits for sure. Otherwise, two separate issues. I would search for �cam deviations� and find some threads to read up on it.
Sounds good! I really appreciate all your advice. I will perform the Solenoid testing - Ohms, 9V battery test again, and computer for the burned resistor. I really hope there are no more issues. I keep on getting the P1124 code as well. I had P0446, but I opened the EVAP system and cleaned the sensor, the vacuum line by blowing compressed Air so far the P0446 has not come back yet.
The computer looks good. No burns. I noticed the connector to the solenoid the wire was slightly cut and I accidentally ended up breaking the connection. I have to get a tool from thr shop tomorrow to get the pins out and re do the wires.
lol definitely!!
so the solenoid male plug had a stripped wire and it ended up breaking off.. I can�t depin it and take the pin out to rewire I got that new universal male and female connector.. you think this would be good? I would have to rewire the solenoid and wires from male and female connector. or would you know the part number and where I can order this from?
The bare pins r available but simeone smarter them me would have to id them. Also u may be able to call dc auto or la dismantler and get them to cut the plug off a wrecked car.
All the wines connections are checked out. The last try would be to do an engine flush to see if the actuator or solenoid works. If not, then it's off to the dealer for repair.
@Mike Murphy
Hi Mike, I need your advice. I'm a bit confused. So, I replaced the connection for the bank 1 solenoid and checked all the connections going back to the DME. The other day, randomly, after putting in gas in the car, the CEL cleared but came back after 20 miles. Then I had the Foxwell scanner and came across a drive link active testing option in which I was able to test the bank one solenoid by sending the signal. The RPM dropped on the car, and it cleared the CEL right away. I drove the car for another 20 miles, and it's back on now. I have tried sending single through the Forwell scanner, and the rpm drops, but the CEL sign is still there. What do you think this could be?
The car drives fine and doesn't drop the rpm..
I'm happy to help, but I'm not the expert. I have some comments and some questions:
First, when this first happened to me, I found a thread in the Boxster section where someone drove the heck out of the car and the problem went away. I think that had something to do with that car sitting a lot and possibly had some sludge buildup due to poor maintenance. So if your car has been sitting a lot, consider the above. If you suspect the engine needs a thorough cleaning, consider SeaFoam oil treatment and maybe a couple of back to back oil changes and run the car hard after being fully warmed up (at least 20 mins).
However, the P1531 code is probably just a bad solenoid. As experts have said, these codes are very specific, and if there is something else wrong, it would likely show a different code.
Lastly, if your cam deviations are more than 6 degrees out of spec, since you have to go and change that solenoid probably anyway now might be the time to replace the tensioner pads (all 4 of them, two per side).
The only thing I can think of with your CEL is that you have an intermittent problem.
I would fine a good shop to take your car to and make sure they diag your car properly and systematically and if they find a bad solenoid and they check the tensioner pads, they will hopefully only replace what's needed and not perform any guesswork repairs.
I hope this helps
Hi Mike, as always, thank you for your feedback! The car definitely sat for a while as a 1998 with 38k miles on it. I will try the seafoam oil flush to see if it loosens the actuator or solenoid. The other confusing part is that when I can the car with just the ODB scanner option, I get code P1530, but when I run it via the Porsche program in the Forwell scanner, it gives P1531. I'll check the deviations again. This will be my last attempt to fix it myself. After this, I will take it to the dealer. Finding a local Porsche tech out here that can be trusted is hard.
Interesting - a P1530 is one bank, the P1531 is the other bank. It would be strange to have both solenoids / actuators bad at the same time, although mine failed 6 months apart from one another. They do share the same common ground and DME though, so I can see how one might affect the other.
