amr89c4

Had a wild day at the office, so I hopped in the C4 for a drive to forget all my troubles. Wild day continued. I now have a C4 that now has enough warning lights and warning buzzers to shame an ambulance!

Well its not THAT bad, but I am hoping its something simple. Nothing seems simple with 911s though. I thought maybe I would get a Oh yeah, I had that happen so check this out. If not, I suppose I get out the ohm meter this weekend and get to work.

I was driving along and everything was just fine on a little back country twisty road. I had not run faster than 80 the whole time and frankly was behaving myself for a change. I was running about 40-50 on a straight away and suddenly the Interlock warning, the ABS warning, the Central Warning and the warning horn all came on at once. Car was and still runs and brakes perfectly. No noise, no smoke, no nothing. Just warning lights.

The only thing I noticed after driving 15 miles back home was that when I cut the car off, and restarted, the lights were off. However, the warning lights and warning horn came back on at around 10-15 mph. Car runs and brakes perfectly. I did notice in the garage that the High Pressure Pump is not running for a few seconds like it usually does with the key on. Hoping its a fuse or relay and will check those tomorrow.

Anyone experience this?

1989 C4
5 speed
51,000 miles

Thanks gang,

Lynn

ilko

Have you checked your brake fluid level?

amr89c4

Yes, the reservoir is full to the maximum line. No leaks anywhere in the luggage compartment, nor on the garage floor. Pedal is firm and feels like it always has.

Lynn

Southampton76

I had the same problem, still do actually. Its brake fluid, or sensor related. Fill the bugger all the way up. Cures mine every time.

Check for fluid loss down by the pedals.

Mark

shophobbit

I had something similar happen this last weekend. After a break in oil change the entire tree lit up including the washer level lights. I check the voltage on the battery and it was down to 12.4. In reading other posts I read the system likes 12.6 or better and/or the problem may be related to a misconnected spark plug. (I had pulled a couple in the process to check for leaks.

I charged the battery and double checked the connectors and all was well after that.

Good luck.

911URGE

Do you have access to a Hammer or OBD1 scantool interface? I would be checking for the presence of any error codes.

I have experienced similar behavior and see fault code 13 or 43 "Implausible signal" usually after driving hard on twisty roads or during AutoX events.

amr89c4

I appreciate the advice. I am still suspicious of the high pressure pump that isn't running now with the key on. It used to always run for a few seconds as I recall.

The fluid is good and no leaks that I can find.

The car did sit for about 3 weeks so I will check the battery. I read in an article by Adrian Streather regarding 964 AWD and ABS systems that an under voltage condition (less than 9.9VDC) will cause the interlock and ABS lamps will come on as well as the yellow traction control LED in the center console. He did not indicate the master alarm light or warning horn would sound.

He does describe the interlock, ABS, master warning and horn warning as a PDAS or ABS system failure. This combination of warnings advises the driver that a component failure has been detected in either the PDAS or ABS systems and that both have been disabled. Apparently the ABS valve and system power interlock relay on the ABS hydraulic unit will be de-energized and power will be removed from the control unit intil the problem is rectified. That doesn't sound good.

Thanks,
Lynn

Scamper

Sounds like a similar problem to mine...although my pump runs fine as expected on start up.

My symptoms included loss of ABS (lots of tyre smoke when "testing"). Narrowed it down to the ABS speed sensors, which I removed and cleaned. Note though that these have allen key heads and are most likely rusted into place, the fronts were the worst as they have a copper earth wire attached which increases the likelyhood of rusting solid.

My sensors were coated in coated in grime and metal filings (they are magnetic) - just come back from a 10 mile shakedown run and the dreaded lights/warnings havent returned (so far!!!)

HTH

Ade

dfinnegan

I've recently been researching a very similar issue here on Rennlist and took some brief notes on the types of issues/resolutions that others have experienced showing similar results.

amr89c4

I found today that the hi pressure pump was working at key on, just like always. I hoped whatever gremlin caused it not to turn on yesterday would manifest itself, but it did not. It also did not solve the problem either.

I also noted that once you cut the car off and restart the warning lights and buzzer do not activate. I can switch the interlock on and the amber blinking light works as designed. I can also deactivate the interlock, too. All is normal until you drive off. Sometimes you get 100' down the road, sometimes 300', but then the lights and warning buzzer come on.

Like yesterday, the car runs, brakes and behaves like nothing is wrong.

The Porsche dealer and Porsche independent garages are all 70 miles away in Austin. Think I'll continue investigating electrical circuits before I jump to a garage. Can anyone recommend a knowledgeable independent Porsche techniciang or garage that knows these older cars in the Austin area?

Thanks,
Lynn

frankvan

I've had the same problem for a few months now and I'm lurking on this thread to see if there are any resolutions to the problem. This problem has been mentioned several times before and seems to be a fairly common problem with C4's?

As with most problems it's intermittent and rears its ugly head at seemingly random times. Things I've tried to narrow it down to:
I've checked the brake fluid level, all the ground contacts and the double red wire that comes off the positive battery terminal. I've cleaned the accelerometers (just don't look at the replacement cost of these or you won't want to open them up!). I've also cleaned all the connectors to the booster and the ABS control units.
When it happens? it can happen right at start up, when starting off the line, when shifting or just coasting along. Because it happens sometimes at startup I think the wheel sensors are probably alright.
Voltage drop? I haven't hooked up a voltmeter yet but I don't notice any dimming of headlights or dash lights when it happens. I should put a multimeter on the battery to check the actual voltages (eg idling, engine off)
Weather? It seems to happen equally in all weather conditions.
Relays? I replaced the ABS and the booster pump relays in the main relay block (51 and 34 I think), replaced fuse 15 even though the old one was fine and cleaned the contacts of the two heavy duty relays on the actual ABS unit. This has actually seemed to make it happen more frequently!

THe only thing I've done to the car recently is a valve adjustment and replaced the O2 sensor - which shouldn't affect the PDAS?!

If I get a chance I'll check the battery voltages and pull the error codes with the scantool (I've pulled them before, just can't remember what the code was).

amr89c4

I have only had the car since Sept 1 and have been perusing this forum since before then, but hadn't really noticed it being a prevalent problem area. A broad search for warning lights turns up a few cases and in most instances the cure was cleaning corroded terminals, corroded pin connections, brake fluid levels and a few wheel sensors. Seems the relays and fuses are more bullet proof than anything else. Replacing most hi dollar parts had no effect in the cases I read. Keep in mind there were pages of warning light issues, but only a few had the exact same symptoms as I have described in the 3 pages I have researched.

I'm going out now to clean grounds, battery terminals, and pin connections. The voltage running at idle is about 13.8VDC. I will keep everyone posted.

Thanks for the help

Lynn

amr89c4

Hi gang!

Last night and this morning I spent about 2 hours cleaning grond wire terminals for the ABS, Interlock and Hi Pressure Pump systems. I pulled the battery cables and cleaned the posts and the cable clamps. I pulled and cleaned the ABS Control Units 55 pin connector and found 4 corroded pins on the unit and the plug. I was confident that this was the trouble as some guys had found corrosion there, cleaned the pins and the problem went away. Not for this 911 jockey, though. No Joy.

I pulled all the ABS and Interlock relays and fuses, checked their contacts and all were clean but cleaned them with contact cleaner anyway.

The car had sat for 3 weeks and the battery while having plenty of cranking power measured low. So, I charged it all night and til noon today. Good hot battery at 13.8VDC, but no help. I got halfway down our short street and the lights and alarm came on. Sigh.

I have done all I can do under the luggage hood without replacing parts. Today I moved on to pulling the wheels and cleaning all the speed sensors. All four sensors looked like new and I was luckier than some as the retainer bolts came out easily. All the sensor grounds looked good, too. While I was at it, I detailed the wheels the wheels and at least that was a successful venture. Just finished up and test drove the car. Same thing, warning lights and alarm 300 feet from the house at less than 20mph. Since that didn't work, than my next move is to take a look at the lateral and longitudinal accelerometers and replace the distributor caps even though they look like new.

After that, its either wait for my Adrian Streathers service procedures book to come in so I can dig deeper with the support of the manual, or take it to a shop in Austin. Since everyone says its completely safe to drive with the lights on (provided there truly is no discernable issue) I will probably wait. Hooking it up to a Bosch Hammer (code tool) was recommended, but I haven't found anyone that has one. Since I am planning on keeping the car, I may just bite the bullet and buy one.

Does anyone rent their Hammer? Does anyone want to sell their Hammer?

Thanks,

Lynn

wf758

I noticed you checked them, but did you clean your accelerometers? I had a similar (but not exactly the same issue) for three years that was finally remedied after cleaning the accelerometers (shop did it for me...took multiple cleanings).

Good luck.

W

amr89c4

Hi Will,

No, I have not cleaned them but the accelerometers are next on the list. I will pull them and see if cleaning them is more than I want to undertake. Glad you got yours repaired.

Lynn