I am desperately troubleshooting my 96 A4 2.8 quattro auto (not starting, no spark).

2 strange things that I can see:
a) RPM in VAGcom move when gas pedal is pressed
b) MIL/CEL light does NOT come when ignition is turned on

VAGcom shows only codes in
- auto trans: 1 Fault Found:
00526 - Brake Light Switch-F
27-00 - Implausible Signal
- auto HVAC: 4 Faults Found:
01297 - Sensor for Vent Temperature; Footwell (G192)
30-00 - Open or Short to Plus
01296 - Sensor for Vent Temperature; Center (G191)
30-00 - Open or Short to Plus
01206 - Signal for Duration of Ignition Off Time
27-10 - Implausible Signal - Intermittent
01582 - Signal for Coolant Temperature
30-00 - Open or Short to Plus
- airbags: 4 Faults Found:
65535 - Internal Control Module Memory Error
00-10 - - - Intermittent
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent
00588 - Airbag Igniter; Driver Side (N95)
32-10 - Resistance too High - Intermittent
01025 - Trigger for On Board Diagnostic Lamp; Malfunction
31-10 - Open or Short to Ground - Intermittent

When turning the ignition on, the MIL (or CEL, not sure what the forum lingo is), doe NOT come on.

What can cause the light NOT to come on?

The usual 'no spark' culprits are (please correct, comment, add):
- crankshaft position sensor
- camschaft position sensor
- maybe speed sensor (sits on flexplate I think)

Before replacing sensors: would VAGcom show codes if they do NOT work properly?

What other 'no MIL check light' conditions can I check?

I am pretty much at the end of my wisdom after 10 days of checking/searching.

 

Check ur ignition ground, the suprossor, if that fuse is blown u will not get a cel, right be ur igntion coil there's a wire with lil box, if that is not grouned or ripped ur car will not give spark or start but crank onlly I had that prob, all it was was a new fuse and supresor from random junkyard car, conected it never had a prob,

 

do you remember which fuse?

 

It sure sounds like the ECU is malfunctioning, since the ECU controls the CEL. Also, your VAG-COM connects to it OK I assume, but the throttle angle signal showing up as RPM is wrong. Start with cleaning all connections at the ECU and then reconnect battery, try again.

 

Here are is the newest code scan:

Friday,19,November,2010,17:26:14:22662
VCDS Version: Release 10.6.1
Data version: 20100831



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Chassis Type: 8D - Audi A4 B5
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77

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Address 01: Engine Labels: None
Part No: 8D0 906 266 B
Component: 2,8l V6/2V MPI OBD2 D01
Coding: 01251
Shop #: WSC 06325
VCID: 2B5BF371F377

No fault code found.
Readiness: N/A

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Address 02: Auto Trans Labels: 01V-927-156.lbl
Part No: 8D0 927 156 J
Component: AG5 01V 2.8l2V US D89
Coding: 00000
Shop #: WSC 00000
VCID: 3469E80D2E49

No fault code found.

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Address 03: ABS Brakes Labels: 4D0-907-379-ABS.lbl
Part No: 4D0 907 379 J
Component: ABS/EDS BOSCH 5 7679
Shop #: BB 37679
VCID: 356FD5092533

No fault code found.

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Address 08: Auto HVAC Labels: 8L0-820-043-2D.lbl
Part No: 8L0 820 043 D
Component: A4 KLIMAVOLLAUTOMAT_D75
Coding: 04162
Shop #: WSC 06325
VCID: 29570979F98B

4 Faults Found:
01297 - Sensor for Vent Temperature; Footwell (G192)
30-00 - Open or Short to Plus
01296 - Sensor for Vent Temperature; Center (G191)
30-00 - Open or Short to Plus
01206 - Signal for Duration of Ignition Off Time
27-10 - Implausible Signal - Intermittent
01582 - Signal for Coolant Temperature
30-00 - Open or Short to Plus

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 8A0-959-655.lbl
Part No: 8A0 959 655 D
Component: Airbag V AUDI D00
Coding: 00127
Shop #: WSC 06334
VCID: 3469E80D2E49

4 Faults Found:
65535 - Internal Control Module Memory Error
00-10 - - - Intermittent
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent
00588 - Airbag Igniter; Driver Side (N95)
32-10 - Resistance too High - Intermittent
01025 - Trigger for On Board Diagnostic Lamp; Malfunction
31-10 - Open or Short to Ground - Intermittent

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 8D0-919-0xx-17.lbl
Part No: 8D0 919 035 G
Component: B5-KOMBIINSTRUMENT D08
Coding: 00262
Shop #: WSC 02032
VCID: 2E5DFA65C065

No Faults Found
or DTCs not supported by controller
or a communication error occurred

End ---------------------------------------------------------------------

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Address 01: DTCs cleared

 

Someone suggested the following, but won't explain how to do it (or what is really meant).

Can someone help me?

"You can check the MIL bulb with DVOM or with outputs in 17-03 go/next [VAGcom]

More then likely the following to be verified, a bad G28 [ground?], or in some MPI a bad ecu supply voltage relay [location?], or ignition switch [location?] during the crank circuit killing 15 [what is that and where? A fuse?]

DVOM will verify volts on G28 during crank regardless of ecu.

Check the key switch and supply relay first. [location? how to check?]'