major electrical problem

[prplhz96]

alright I posted before on this, but now I am going to give the whole story. I purchased last week another 92 TSI AWD, which needed a head/timing. After head/timing was installed, the car would not turn over. I noticed that the car had an aftermarket alarm system, so I COMPLETELY removed it, triple checked that every wire was of factory and not anything to do with the alarm. So I proceed to start her again, she purrs like a kitten, beautiful idle, perfect. After about 15-20 secs. of running the CEL comes on, so I immediately shut it down. Then I went over everything and nothing seemed out of place. I tried to start again, nothing. Starter turns, but no spark/no fuel(fuel in rail, just not into cylinders). First thing i think of is ECU, so I swap with a buddy and with his ECU in my car same problem. My ECU worked fine in his car though. So i move on to testing the CAS, great working condition. Also ALL fuses are good, and MPI relay has power and is clicking with key turned to start. I also tried 2 different loggers(with their own cables), and neither worked, said communication error. They do work fine in the cars they came out of though(both). As far as the major electrical problem.......no headlights, tail lamps, blinkers, horn, wipers, nothing??????? When i depress the brake pedal with the key in the on position, all the lights(dummy) go out, except for the oil light. Also with the key in the off position the oil light comes on when the brake is applied. To complicate this more, a relay under the dash, is buzzing like crazy(it is a black relay, next to it is a blue relay on one side and a black one on the other) they are above the clutch pedal. The oil light and buzzing relay completely stop when the clutch pedal is completely applied to the floor. I hope you are getting this so far. So I have 2 different problems I think, electrical and no start. Any help would be appreciated, because I need it. Thank You

 

[GTM]

alright I posted before on this, but now I am going to give the whole story. I purchased last week another 92 TSI AWD, which needed a head/timing. After head/timing was installed, the car would not turn over. I noticed that the car had an aftermarket alarm system, so I COMPLETELY removed it, triple checked that every wire was of factory and not anything to do with the alarm. So I proceed to start her again, she purrs like a kitten, beautiful idle, perfect. After about 15-20 secs. of running the CEL comes on, so I immediately shut it down.
...

You of course understand that on one can solve this problem but you or a professional mechanic with their hands on the car. There is very little doubt that you have connected some wires wrong when you removed the alarm. There is a remote possibility that you failed to connect the battery ground at the starter and thus routed engine ground through the accelerator cable, possibly clutch pedal linkage and wiring harness. When the loom got too hot it melted into some of the power feed wires and now you have shorts. Unless you want to spend days or weeks at this you MUST buy a short finder and learn how to use it. You will need at least 1 standard test light and another with a wire piercing probe. You will also need an inductive ammeter.

Unplug the rear harness, unplug headlights, parking lights etc. as many sub harnesses as possible that are unrelated to start/run condition. With the key out of the ignition, all doors closed, all switches turned to off. Connect your test light through the negative battery cable and the battery post. It will light and then may grow dimmer as it starts the clock and fills some of the electrical components. If it doesn't change then hook a jumper wire from the negative battery post and the negative battery cable. Using you inductive ammeter read the current flow, reverse the ammeter so you can get an average. You can use a multi-meter with a 10 amp circuit test in series to substitute for the jumper for this test. This must be less than 1 amp with everything off and you should see the difference when you open a car door. Once you have established this is good you can then turn the key to on and check with short finder and the inductive ammeter when you connect the battery.

You may have to unplug all the relays and then add them back one at a time, you may have to reverse the add order in case one is activating another. It is a slow labor intensive process but it's about the only way you will find this if you have burned and shorted wires out inside a loom. If you have to cut apart taped looms when working with the short finder do retape everything or you will have one ugly mess.

Good luck, let us know what you find.
GTM

 

[DrunkMOnk]

That's wierd, I have a similar electrical problem on a 1G I just bought , I also pulled an alarm off my car, and first of all my starter wont turn over my brand new rebuilt engine. And once current from the charger is placed on the battey, that same buzzer that you have is coming on, and it goes off as soon as I depress the clutch. When I put the key in the on position, every idiot light comes on..Other that that though, everthing else works fine, I have no idea what it could be. Before the rebuild everything worked fine.

 

[greycar]

This should be easy, and I have seen it happen before. Did you check you battery?????????????? positive and negative terminals. make should everything is tight and very clean so you get good contact. Also whats you voltage??????????? have you checked it with a multimeter????????????????? Check the voltage at the battery termianls not the battery post while you are cranking, if you get a drastic drop you found your problem. I can almost gaurentee that it is a stupid problem, 92s have good electrics and there aren't like the crappy 90s

 

[GTM]

This should be easy, and I have seen it happen before. Did you check you battery?????????????? positive and negative terminals. make should everything is tight and very clean so you get good contact. Also whats you voltage??????????? have you checked it with a multimeter????????????????? Check the voltage at the battery termianls not the battery post while you are cranking, if you get a drastic drop you found your problem. I can almost gaurentee that it is a stupid problem, 92s have good electrics and there aren't like the crappy 90s

The falacy in that argument does not address how it's possible for the oil light to come on with the key off but we all know how simple that is. Want me to give you a hint or are we to be blessed with with more broad sweeping brushes.

I did not stress that he has in all probability connected a wire to a _floating ground_ in the bulb check circuit. Since I don't have the schematic nor know what was done when the alarm was removed I can only guess this is what started the problem. However it is yet another circuit which was taken out as a result of that connection for the evidence is he had it running long enough to smoke something yet has indicated all fuses are good. And yes he could substitute this module for another it would be wise to take his module and try in another car lest he smoke his buddies and have 2 dead cars.

By all means he should clean battery connections but I would be surprised if this solves this particular problem for he had it running and the oil light comes on with the key off but we can hope it will be that simple.

Cheers,
GTM

 

[prplhz96]

thanks for the help, I have some work to do in the garage tonight I guess........will keep you posted

 

[prplhz96]

little update if it helps(or adds to the problems). While changing the coolant temp. sensor, I touched teh ABS unit module, with the wrench that was on the sensor, causing a spark. I'm like, wtf. I know this isent right, so i unplugged the abs fuse(under hood), and the car wont turn over, but the module is no longer"hot". I replaced fuse at it cranked again, no start, just cranking like before. This means I have an open circuit somewhere, i am guessing. Also, with my test light grounded on the negative battery terminal, the engine compartment is "hot", every ground on the firewall I put the probe on(with ground wire on negative battery cable), lights the test light. I double checked all wires visually, and followed neg. battery cables, everything "looks" fine, I just dont want to tear into anything yet, until I really need too.

 

[GTM]

little update if it helps(or adds to the problems). While changing the coolant temp. sensor, I touched teh ABS unit module, with the wrench that was on the sensor, causing a spark. I'm like, wtf. I know this isent right, so i unplugged the abs fuse(under hood), and the car wont turn over, but the module is no longer"hot".
...
I double checked all wires visually, and followed neg. battery cables, everything "looks" fine, I just dont want to tear into anything yet, until I really need too.

Holy cow, you are right about something is putrid in Peru!!

You have a major malfunction complete with gremlins. You wouldn't be foolin us when it's not April 1st. I'll have to think about this and get back later this evening for it's dinner time and we have company. This is a first case in over 20,000 cars I've worked on so I got to rack the gray matter how this could be.

Maybe someone else can jump in here while I'm off line.

Cheers,
GTM

 

[DrunkMOnk]

Let me know when you get a handle on this, so I have a good base to run from when I start troubleshooting mine..

::edit::

if you need a wiring schematic, let me know and I will email you the PDF file

 

[GTM]

little update if it helps(or adds to the problems). While changing the coolant temp. sensor, I touched teh ABS unit module, with the wrench that was on the sensor, causing a spark. I'm like, wtf.

The ABS is connected to metal brake lines which are somewhat insulated with plastic guides and rubber hose at suspension parts. Should a short have occurred within the ABS unit it conceivably could be hot and yet insulated. However if the bulb check module or one of these numerous floating grounds has been energized when re-connecting wires from the discarded alarm this could be a source. I'm back to my original post where I indicated unplugging the rear harness from the front, this cuts your searching in half. But if you want to jump the gun on this try unplugging the ABS harness and install the fuse, using test light again on ABS housings. If it's still hot then that's not it...

I know this isent right, so i unplugged the abs fuse(under hood), and the car wont turn over, but the module is no longer"hot". I replaced fuse at it cranked again, no start, just cranking like before. This means I have an open circuit somewhere, i am guessing.

Woah, just remember many years ago a brake light switch on a master cylinder shorting out and causing weird problems, this was long before bulb checks and ABS. In this case the ABS and the master are direct connected with metal lines, the brake lights on some cars is wired independent of the ignition switch thus hot all the time. This is also wired into the bulb check module to warn of ABS problems. I'm still thinking how/why the oil pressure light is getting power and this too is on the check module and those floating grounds. Thinking out loud, the oil pressure sensor is NOT the same as the gauge sending unit which I'm sure if it is wired into the check module. My son's wire broke once while I was in the car and he panicked until I asked about the light and any engine noise difference. My point is this circuit is finding power, passing through the switch and going to ground. Again back to floating ground and alarm wires.

Also, with my test light grounded on the negative battery terminal, the engine compartment is "hot", every ground on the firewall I put the probe on(with ground wire on negative battery cable), lights the test light. I double checked all wires visually, and followed neg. battery cables, everything "looks" fine, I just dont want to tear into anything yet, until I really need too.

You threw me a curve for a while on that one, of course it would all appear hot _IF_ the ground cable is off the battery for that leaves only the test light to complete the circuit from positive through the clock, radio, and various other components which need to be saturated to their respective grounds. This was the test I had suggested in the original post, now if you have a multi-meter with a 10 amp test circuit you can check again using the probe to the negative battery without the cable but everything off and doors closed. You want to know how many amps (or watts) are being drained AFTER all those components have been saturated. If necessary unplug the power antenna for they can do strange things depending on circuit design and the 555 clock chip. This has nothing to do with the wrench and the ABS issue.

It would be good to know which is most positive the engine block or the ABS unit, put a meter on it to check for polarity, this could be another clue. As I've posted elsewhere the bulb check module is the most sophisticated circuit on todays cars and I don't think any singular design EE can think one of these through without looking at a schematic. Of course I'm not including the brain box and other components like radios etc. I have had the dubious honor of having repaired a few and diagnosed what body shops have done to hot wire combination rear lamps. I've seen mechanics get so frustrated over this circuit that they just get out the side cutters and start cutting wires... resist the temptation.

Hope there is something in there which proves to be useful, keep us updated and any progress or new conditions you discover. Do take notes especially when working with the conditional floating grounds for one time they can have current flowing in one direction and then have it reverse and take yet another path to complete the circuit.

Cheers,
GTM

 

[GTM]

Let me know when you get a handle on this, so I have a good base to run from when I start troubleshooting mine..

::edit::

if you need a wiring schematic, let me know and I will email you the PDF file

Hmmm, how much of what you have read is identical to your problem?

I'm leaning in the direction that the bub check module is out to lunch OR he's tied what he thought was a ground into what is best described as a conditional ground or floating ground. But I also think that in addition to that he has a short but that could be every time he turns the key on it starts the bulb check sequence and one of those conditionals is feeding another circuit or relay which should not be energized at that moment, it locks on and feeds other circuits until the key is turned off. If either of you don't have this resolved in the next day or so I'll take you up on the (generous?? hehehe) offer of the schematic(s)

Someone sent me a copy of the module a couple of years back when he was having a bunch of problems but forgot what they were and where I stashed the PDF. Nothing like these though. Unfortunately nobody has written a text book on diagnosing one of these little boxes and all the possible logic branches... don't look at me.

Cheers,
GTM

 

[DrunkMOnk]

Well my car is fixed, the starter wire was connected on the wrong pole, that will do it.

 

[GTM]

Well my car is fixed, the starter wire was connected on the wrong pole, that will do it.

What, can you explain this a little better? Was this at the starter which has the battery cable and the starter solenoid wire, I didn't think there was any possible other connections.

Ahha, were you talking under the dash where you removed the alarm and re-connected wires where you thought they should go. The one you checked 3 times before and assured us they were correct... never a dull moment eh.

Is everything working fine, car runs good?

Cheers,
GTM

 

[DrunkMOnk]

Sorry, I was in a rush and couldnt be more specific. The starter has a wire comining out of it and 2 poles (I could be wrong as i am going off of memory) the wire coming off of the starter was connected to the wrong pole, which i believe in turn led us to connect the power wire to the wrong pole. This caused the car to act really funny.