grantvs911

Hi all, thank-you in advance for your help with my confusing 964 electronics issue.

My 1990 C4 was working beautifully when I had it out Tuesday on a very warm summer day, it performed flawlessly and showed no signs of having any issues. I drove it home, washed it down and parked it for the night. In the morning I decided to install a new Optima red top battery. After installing I hopped in the car and cranked it up... it cranked but wouldn't catch. I replaced the DME relay, changed the battery back to the old one, still encountered the same issue. FYI, the dash lights come on as expected but I notice that the tach does not move when the engine is being cranked.

I decided to deal with the issue later and tried to lock up with the remote fob (the car has an aftermarket BergvillFX t-Lock keyless entry installed) The remote wouldn't allow me to lock it up. It will unlock the car but not lock it. That was my first clue that the issue is likely to do with the locking mechanism (Maybe???)

I know that a cranking non-starting engine could be any number of things from coil packs to fuel pump. The battery is strong, that's not the issue and I doubt it would be fuel filter related as that was changed recently and the tank is 3/4 full with fresh gas. I replaced the keyless remote batteries and went down with the spare set of keys & extra remote and encountered the same issue. I pulled down the BergvillFX keyless entry and electric lock control boxes from below the dash. All wires are as they should be, nothing out of place. So I dug deeper. When I opened the electronic lock control module and used the remote fob to operate the keyless entry the solenoid inside the box works as one would expect for the opening function but when I push the lock button I get a noise but the solenoid does not engage fully in the same way as when the open button is pushed.

One other odd behavior I noticed; the emergency flasher relay clicks/ticks when I turn the ignition key. It makes the same noise as you would hear if using the turn signal. I installed a new Porsche relay for the emergency flasher (position R32 in my cars fusebox) and the DME as mentioned earlier. Neither relay replacement improved a thing.

I am guessing that the factory installed car theft immobilizer is being fooled by the non functioning electronic lock control module... could this be the case? Does anyone know how the two units interact. I would love some help with this unusual problem. There's little info on this Sachs electronic lock control module (part number 429-911-618-113-01) on the usual forums. Could it be that I fried this box when changing the battery or somehow shorted something when washing the car? I'd love to know if simply replacing the module would solve my non-start issue. Any thoughts?

I appreciate this forum, such a great place for exchanging knowledge. Thank-you. I'm trying to find a solution quickly so I can get the car out for some fun driving.

Kappi2907

Do you have an alarm? If yes, bypass it if possible. Could be your electronics of the alarm are spoiling wet after rinsing the car.

ToreB

The T-LOCK system has probably nothing to do with this issue, nor the door lock control unit.
The turn signal blinking you observe when you turn on the ignition is not the emergency flasher, but the normal operation of an alarm unit being tripped when the ignition is turned on. It has obviously not been disarmed, which is normally done by unlocking the doors. I guess the alarm unit horn is disconnected or faulty. An armed alarm unit will normally disable either the start motor or ignition, or both.
I would start with locating the alarm unit, do measurements on why it is not disarmed, or bypass it. If it is the original Porsche alarm, it is located a bit inaccessible under the windscreen, behind the right frunk gas strut.
Cheers,
Tore

grantvs911

Thank-you Tore & Kappi. The t-Lock system has always worked flawlessly, It wasn't on my list of suspected culprits.

I will now try and work to fix or bypass the factory alarm. I do see it where you describe Tore, not easy to reach.

Cheers,
Grant

grantvs911

Hi all, a quick update, I gained a small victory but the battle isn’t over yet.


After turning the door lock rapidly three times it seems that I was able to reset the locks. The clicking noise from the flasher relay went away and I am now able to both lock and unlock the car with the BergvillFX remote keyless t-Lock system as before. Unfortunately I am still unable to get the car to spark up, likely from no power getting to the fuel pump? It cranks strongly and the battery is fully charged but there is no RPM being shown on the tach when cranking the engine. (I forgot to take a photo of the dash lights but my memory says that there wasn’t a "Check Engine” light illuminated)

The areas under the seats are bone dry, the glove box was fully closed. There’s no smell of gas as one might expect if there was a coil issue. I’m leaning to a failed factory alarm immobilizer as the potential culprit at this point. I have an alarm tech coming over to try & bypass the factory unit. Would readers agree that this is the next place to start and from experience what suggestions might you have to either bypass or replace the factory immobilizer unit?

bw-porsche

It sounds to me that it could well be the crank sensor. It can be checked to see if it is working. Check on other threads concerning this. Ask me how I know!

klokwerk

My money is on the crank sensor too.
Also check that sensor's harness to make sure it's not crumbling or needs a new connector.

grantvs911

Thank you Klokwerk & BW, you could be right. The tach doesn't show any movement when I turn the engine over, this is one sign that points in that direction.

What's making me think it's perhaps not the crank sensor are the electronic issues I was initially having. The remote central lock wouldn't work correctly and the ticking sound from the alarm relay going off (the alarm horn has been removed). I have a rebuilt engine in the car, completed in 2017. The crank sensor was replaced at that time. I wouldn't think it would be needing replacement after 5 years but I could well be wrong.

Can anyone share how to bypass or test the alarm easily? And has anyone removed their alarm and replaced with an easy to use option? I'm hearing that the alarm module can cause these types of faults, I'd like to go with something bombproof if it needs replacement. It would be nice to do a simple test if possible beforehand to know if this is indeed the issue.

klokwerk

My sensor needed replacing after about 5 years.

grantvs911

Thanks Klokwerk. Good to know. I've tried doing the alarm bypass (didn't work) and have done the DME module multimeter test for the crank sensor with results that were outside of what I understand are normal. That test along with the fact that my tach doesn't move when cranking the engine has me firmly believing that you are indeed correct. I have a new crank sensor in my hands, I just need time to install it with the correct gap. I'll let you know the result.

budge96

My money's on the crank sensor just replaced two myself ... Bert

grantvs911

Hi all, an update on this issue. I had the car towed at great trouble from my deep underground parking and taken to the local shop I use. They had the problem solved in 10 minutes... a faulty DME relay. It turns out that the replacement DME I purchased a few weeks earlier and installed myself was a faulty relay. The shop was great but what a pain, such an easy fix for me to have done myself. I'm ordering a solid state version ASAP.

bw-porsche

Glad to hear you have found the problem. I have one of the solid state type DME also.

klokwerk

Great news. But when you mentioned in your first post that you'd replaced the DME, I'd assumed you replaced it just then. Either way, new DME as the fix is good. Also, have the solid state unit, works great.
I do keep a brand new regular DME around just in case.

grantvs911

Thanks & yes, I HAD replaced the DME with a "new" one on the 1st of Aug. Turns out that the new one was a dud straight from the factory. Lesson learned, don't trust new parts 🤣