95 jetta 2.0 no check engine light, bulb is good and fuse 15 is good. all other fuses good. no spark and no power to coil. battery is fully charged. It was running until I had the battery disconnected. now it cranks but wont start. any ideas? does the alarm interfere with the ignition?

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Check fuses and look for a main fuse on the positive battery terminal.

https://www.google.com/search?q=volkswagen+jetta+mk2+fuse+box+diagram

no, no and no the PCM is not bad.
OkAY
forget the past what matters is here and now
I guess the engine starter motor cranks fast and loud
but the engine fails to start and run and stay running
or does run for 1 to 10 seconds and the IMMO fails and cuts fuel dead (by design) and the IMMO lamp is glowing and this glow means IMMO IS NOT HAPPY.
this car stalls in 2seconds, if IMMO fails.

for Immo to work security key immoblizer
here is list.

1. cars main battery fully charged, even if the battery is new it must be fully charged so all computer in the car are happy and at 10v they all fail. step 1 in all service manuals made say that.
2. the key must be good.
3. if key fails 3 things happen , immo blinks wrong, scans show IMMO is failing key or models and the engine will not start. (over 10 seconds long)
4. all fuses good ,now, only now matters. (physics)

your post said and matters huge this.
cannot detect the key<< well it did not lie to you.
if main under hood battery is charged.fully.
I will now read your lost users manual now.
to you.
page 16 topic
Sentry Key® Immobilizer system
car came new with 2 good keys try #2 yet???????

now page 16 direct quote to you
"After placing the ignition to the ON/RUN position, the
Vehicle Security Light will turn on for three seconds for a bulb check. If the light remains on after the bulb check, it indicates that there is a problem with the electronics. In addition, if the light begins to flash after the bulb check, it indicates that someone used an invalid Key Fob to start the engine. Either of these conditions will result in the engine being shut off after two seconds."

use the 2nd key now
scan the PCM if it says key is bad it is bad and the dash told you it was.
or the battery is too LOW, so charge the battery up fully and test again.
a rested good battery is 12.6vdc
if cranking battery voltage drops too low to 10vdc the battery is weak.
batteries not used for a long time can go bad

not told you when was the last time car ran perfect.
last week ,year, or?

There isn't one. The engine malfunction light is generated by the Engine Control Module (ECM) to show faults that the 'computer' has found. If the bulb has gone, you change it. If the light isn't lighting up, that's good.

Fuse box Volkswagen Jetta 6 - Fuses box diagram

https://fusesdiagram.com > volkswagen > fuses-and-rela...

Fuses and relay Volkswagen Jetta 6. For the Volkswagen Jetta 2011, 2012, 2013, 2015, 2016 model year.

FUSE PANEL LOCATION
The fuse panel is located in the engine compartment. A label on the inside of the cover lists the fuse amperage and circuits protected.
volvo 850 fuses fuse panel layout service repair manual
FUSE PANEL IDENTIFICATION
Fig. 1: Fuse Panel Identification
Courtesy of Volvo Cars of North America.
WARNING: Always disconnect battery ground cable before servicing "high-current fuses. It is recommended that "high-current" fuses be replaced by a qualified technician.
* 1 - 15 Amp
Fuel Injection, Distributor Ignition, Automatic Gearbox
* 2 - 15 Amp
Fuel Pump, Alarm System
* 3 - 10 Amp
Courtesy Lights, Oil Level Sensor
* 4 - Not Used (1993-95)
* 4 - 10 Amp (1996)
Electronic Start Inhibitor (Immobilizer)
* 5 - 30 Amp
ECC Blower (Speed 4)
* 6 - 25 Amp
Central Locking System, Alarm
* 7 - 15 Amp
Audio System (Amplifier)
* 8 - 25 Amp (1993-95)
Power Antenna, Trailer Connector
* 8 - 40 Amp (1996)
Electronic Start Inhibitor (Immobilizer)
* 9 - 30 Amp
ABS, Traction Control System
* 10 - Not Used (1993-95)
* 10 - 15 Amp (1996)
Heated Rear Seat (If Equipped)
* 11 - 30 Amp
Heated Rear Window & Side Mirrors
* 12 - 10 Amp
Brake Lights
* 13 - 15 Amp
Hazard Flashers, Headlight Flashers, Alarm
* 14 - 30 Amp
ABS, Traction Control System
* 15 - 10 Amp (1993-95)
Audio System, Courtesy Lights, Door Open Light, Trunk Light, Glove Box Light, Remote Control Central Locking System,
Oil Level Sensor, Seat Belt Reminder
* 15 - 10 Amp (1996)
Audio System, Courtesy Lights, Door Open Light, Trunk Light, Glove Box Light, Remote Control Central Locking System,
Oil Level Sensor, Seat Belt Reminder, Data Link Connector
* 16 - 30 Amp (1993-95) Accessories
* 16 - 30 Amp (1996)
Power Antenna, Trailer Connector, Accessories
* 17 - 10 Amp
Key Reminder
* 18 - 25 Amp (1993-95)
Heated Front Seats, Power Mirrors
* 18 - 15 Amp (1996) Front Fog Lamps
* 19 - 15 Amp
Left High Beam Headlight
* 20 - 15 Amp
Right High Beam Headlight, High Beam Indicator
* 21 - 15 Amp
Left Low Beam Headlight
* 22 - 15 Amp
Right Low Beam Headlight
* 23 - 10 Amp
Left Parking Light, License Light
* 24 - 10 Amp
Right Parking Light, Bulb Failure Warning Sensor
* 25 - 10 Amp
Rear Fog Lamps, Fog Lamp Indicator
* 26 - Not Used (1993-95)
* 26 - 25 Amp (1996)
Heated Front Seats, Power Mirrors
* 27 - 15 Amp
Back-Up Lights, Turn Signals
* 28 - 10 Amp
Cruise Control, Heated Rear Window, Seat Belt Reminder Light, Shiftlock, Bulb Failure Warning Sensor, Heated Rear Seat
* 29 - 15 Amp
ABS, Traction Control System
* 30 - 10 Amp
Cigarette Lighter
* 31 - 25 Amp
ECC, ECC Blower (Speeds 1-3)
* 32 - 10 Amp
Audio System, Remote Controlled Central Locking System
* 33 - 15 Amp (1993-95)
Power Seats, OBD Test Socket, Tailgate Washer/Wipe (Wagon)
* 33 - 15 Amp (1996)
Power Seats, Tailgate Washer/Wipe (Wagon)
* 34 - 25 Amp
Windshield Wiper/Washer, Horn, Headlight Washer/Wiper
* 35 - 10 Amp
Instrument Lights, Sun Roof, Traction Control System
* 36 - Not Used
* 37 - Circuit Breaker
Power Windows, Power Sun Roof
* 38 - Not Used
* 39 - Circuit Breaker
Drivers Power Seat
* 40 - Circuit Breaker
Passengers Power Seat
RELAY PANEL LOCATION
The relay panel is located at the left corner of the instrument panel.
i copied this off a volvo site Hope this helps

Not James, but maybe I can help: Under the dash in the fuse/relay box is the ignition coil relay. This sends battery voltage on the black/white wire to all four coils. With key in on, all 4 coils should have power to them on this black/white wire. If no power, check fuse #2, a 15 amp fuse which sends power to the ignition coil relay, and on to the coils when the relay is energized by the ecu/pcm. Only thing else to cause spark is when the ecu/pcm sends a signal to the coil's Ignition Control Module (housed inside each coil assembly), which controls the primary circuit (the black/white wire), and causes high voltage to the spark plugs.

So check the black/white wire to the coils. If power there with key in on, check for spark at a spark plug when cranking the engine over. If power to coils but no spark, possibly a crankshaft position sensor or cam position sensor giving a bad signal to the ecu/pcm. Good luck.

A long list of things. From fuses to ignition switch to ecu to security alarm and more.

Here is how to start looking: Turn the key to on. Do the dash gauges and warning lights and check engine light come on? Then power is getting to the switch and being sent out from it. Next, use a test light and check for power TO the coils and TO the injectors with key on. All four injectors use the same color power wire. My wiring diagram is poor quality, but it looks like a green wire or possibly a gray wire-remember same color power wire to all injectors-the other injector wire is a ground wire, and they are all different colors. Pull one injector connector off and check for power on one terminal with key on. And could do the same at the coil pack. With key on, the white wire with red stripe to the coils should have power-actually, the white wire is spliced and two white wires are shown going to coil pack-this is the primary current to the coils- is hot in run or start.

If no power to coil or injectors, here are the fuses to check: in the under hood fuse/relay block: ecu-10 amp fuse, Eng-15 amp fuse, and these maxi fuses: fuel inj-30 amp fuse, Main- 80 amp fuse, Ign-40 amp fuse. And one more- a designated Main fuse-15 amp fuse.
If these fuses are good, should have power going to injectors and the coil pack with key on. If the key is turning on the dash, some of those fuses are known good, but need to check all of those listed.

I will stop here, and wait for your reply. You get this far, you are on the way to diagnosing the problem.

all fuses good, using ohm meter tests in hand. or better
12v on both ends of fuse key on?
K12a, 16valves, DOHC, chain cam motor.)
well you are on track, no spark, that be real. huh>
the immo (slang for UK immobilizer) for other readers.
so not TDC codes, but that is not all there is, you can attach
a scan tool and see if you have CMP/CKP sigs, and RPM cranking.
crank for 5 seconds to see if these critical to spark parts are in fact working.
single distrib? (the 2 forms of k12a ) a= real japan engine not china.
new cap, new rotor, , no china rotors that mount backwards allowed.?
do you have schematic of your engine EFI?
you really need that, or finding problems can be very hard.
in usa we have 3 major sources here , all on line, to get that fast.
do you? have that in UK? do you have a suz, dealer? with shop man?
we have mitchells,alldata, and chiltons all on line for this.
we also have the for free in public libs here...
diagnosis. (ill assume its flooding) prevents fire and ring damage.
1: i cut the fuel pump by pulling FP relay.
2: then check spark,,if spark is bad to all 4 spark plugs, that's right 4.
then check spark directly at the COIL, some cars have hidden coil.and can be checked, ask.
if spark is bad at coil, HV terminal. then check for Ignitor drive
pulses. if good then coils is bad. (good input, bad output, bad coil)
if the ignitor is dead, check its input, if input bad , ECU is not
sending inputs. this can happen for only few reasons. in no order.
1: bad ecu
2: no cmp or ckp signals.
3: lost power to ECU, fuses,
IF car has dash tachometer, is it dead, cranking , no 300 rpm cranking?
scan too.
RPM dead. cranking.
no CMP /CKP errors cranking from ECU DTC, ERRORS ON SAME.?
That is how i do this, and never fail.
better is:
1: compression good?
2: spark good and timed
3: good fueling?
you fail #2 (lets work that)

check see if power going to ignition coil primary terminal, if not check ignition coil fuse.if power going to ignition coil primary terminal, your coils could be bad or you have ignition module fault or crankshaft position sensor and pcm fault,have vechicle code scanned many things will cause no spark conditions, make sure battery fully charged or in good shape you need good 12.6 volts from battery, for pcm and ignition to work properly.

You can take this off and have it checked out at you r local auto shop. Most likely if you're not getting spark, the coil is bad. You can check it yourself through a backyard mechanic way, but it can give you a shock if not careful. ( a screw driver in the end of a plug wire, holding it close to a metal ground while someone turns the engine over. If you see spark, then the coil is good. Be sure to use a screw driver with a good insulated handle.

Jettas were notorious for electrical issues. I fought with one for 2 years.
The starter relay is on top of the starter in the center rear of the engine compartment near the firewall. Its mounted at the top of the bell housing, underneath the intake and next to the exhaust manifold and hard to get at from both the top and bottom. Personally, I'd take it to a good respectable foreign mechanic. Not worth fighting with