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CarDoc, Independent European Shop owner
Category: Car
Satisfied Customers: 6456
Experience:  20 years of experience working with European cars. Independent European shop owner and technician.
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2002 vw jetta: drove..Belts..lights work..alternator top connector

Customer Question

In my 2002 vw jetta drove to work, no car trouble, after work car wouldn't start. Belts run, radio/lights work but the alternator top connector was unplugged. Plugged alternator connection back, same result, also there is no spark with removed spark plug. Interstate battery is 3 months old.
Submitted: 4 years ago.
Category: Car
Expert:  CarDoc replied 4 years ago.

CarDoc :

Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.

CarDoc :

Ok, so driving normally into work, the car was fine.

CarDoc :

Then you tried to start it after work, did the engine spin over?

JACUSTOMER-g626uxra- : Yes
CarDoc :

Ok, but you did find the single small wire connector not connected to the alternator?

JACUSTOMER-g626uxra- : Meaning belts spun, yes
CarDoc :

and the alternator connector? It was just hanging there?

JACUSTOMER-g626uxra- : Yes, top connector, had fallen off, no attachment with connector
CarDoc :

very odd. I've never seen one just fall off without prior work

CarDoc :

however, let's move on...

JACUSTOMER-g626uxra- : Headlights were replaced 2 weeks prior
CarDoc :

The most common cause of a no-spark condition in these cars is a faulty crankshaft position sensor

CarDoc :

this sensor is bolted to the engine, near the transmission bellhousing, just behind the oil filter

JACUSTOMER-g626uxra- : The unplugged alternator wouldn't be a reason
CarDoc :

very doubtful

JACUSTOMER-g626uxra- : What would happen if there was no connection
CarDoc :

no connection between the small wire and the alternator? The alternator simply wouldn't charge

JACUSTOMER-g626uxra- : Alternator definitely not the fault
CarDoc :

in any answer that I give through this format, on cars that I have not personally diagnosed, nothing is 100%. However, if the battery is showing at least 13.6v with the car running, the alternator is not the issue

JACUSTOMER-g626uxra- : What else would the c.c.s. do
CarDoc :

the ccs?

JACUSTOMER-g626uxra- : Css, sorry crank shft sensor
CarDoc :

Ok, got it. The crank sensor sends what we'll call a pulse in the form of a wave (it's more involved than this) to the engine management computer. This pulse is the only way the computer knows when cylinder #1 is at top dead center, and the only way that the computer will be able to pulse grounds to the coil to fire the spark plugs

JACUSTOMER-g626uxra- : So perhaps, CSS, but maybe coils
CarDoc :

I seriously doubt it's the coil (there is one central coil), and again, if I saw this condition, I would replace the crank sensor, as a result of my experience working on literally hundreds of these cars

JACUSTOMER-g626uxra- : What is the difficult level
CarDoc :

4 on a scale of 1-10, 10 being most difficult. The wire lead from the sensor travels a bit of a distance, so it's just time consuming. Figure about 2 hours for a novice. Also, removing the oil filter helps access

CarDoc :

So hopefully this has sufficiently covered the original question

JACUSTOMER-g626uxra- : And if not
JACUSTOMER-g626uxra- : Meaning is that the only cause, or are there more
CarDoc :

Respectfully, we're working through a format designed to give well-researched answers given by experts very familiar with your particular car. Unfortunately, we cannot go through complex diagnostic paths here due to lack of scan equipment, tooling, mechanical knowledge, and other barriers. I am strongly suggesting that you replace or have your crankshaft position sensor replaced. Your only other option is to have the engine control module scanned for codes to see if there is anything else stored. However, often, failed crank sensors do not throw codes.

JACUSTOMER-g626uxra- : Thanks
CarDoc :

no problem

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