B5 A4 Avant just will not start...

[J.B.Motorwerks]

Hey Guys,

I've got a no start situation on my 2001 A4 Avant Quattro
It started approx. 2 months ago, I just swapped the 5hp19 transmission in it because the original went out, the no start situation started before the swap.
I have no injector pulse AND no spark.
The car IS turning over.
I already replaced the Crankshaft sensor, there is NO communication with VAG-COM
Is there anyone on here that can explain in detail what exactly happens when I turn the key to crank the car for the B5 A4 ignition system specifically?
The only conclusion I can come to is that the ECU is shot.... but this is extremely rare to happen.
I need help with further diagnostics... ANY advice will be GREATLY appreciated!!!! thanks!

[josh.smuin1]

All ground wires, sensors, etc. plugged in? I know these cars are tricky.


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[Avant Nate]

Have you been able to connect to vag-com in the past?
Do you have an aftermarket stereo?
Is your abs light on, and if so, have you tried unplugging the module?
When you turn the key to the on position, does the MIL light illuminate.?

[josh.smuin1]

I've never been able to have access to a vag-com. But yes my ABS light was on due to a bad abs sensor. I was able to clean the light with a snap-on solus ultra with the euro software. But no my car doesn't have the MIL light when I turn the key . No aftermarket stereo.


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[RENOxDECEPTION]

Unplug your ABS module and try vag com again.

[josh.smuin1]

I've never been able to have access to a vag-com. But yes my ABS light was on due to a bad abs sensor. I was able to clean the light with a snap-on solus ultra with the euro software. But no my car doesn't have the MIL light when I turn the key . No aftermarket stereo.


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I swear I'm having an off day. Disregard this


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[walky_talky20]

A: No MIL (CEL) when you turn the key = the ECU did not boot. Period.

B: Your ECU controls both spark and injector pulse.

C: No matter how broken (or not) your ABS module is, it cannot and will not keep the MIL from illuminating during Key ON, Engine OFF state. (Else dead ABS modules would be worth their weight in gold for people needing to pass emissions. Such is not the case.)

Result: You need to check for all power supply circuits to the ECU. Because you did not specify, I'm guessing the car has a 1.8 Liter Turbocharged engine.

The easy things to check first**:
- Check Fuse #7 (10amp). Should be Hot in Run and Start.
- Check Fuse #29 (20amp). Should be Hot in Run and Start.

The harder things that need to be checked before condemning the ECU:
- Check for 12v+ at ECU pin 62. Should be Hot at all times.
- Check for ground at ECU pins 1 and 2.
- With ECU unplugged, check for voltage at ECU harness pin 21. Should be hot in Run or Start.

**By "Check Fuse", I mean to use a meter or test light to check for battery voltage at both top contacts of the fuse while installed in the fuse box. I do not mean to merely remove the fuse and check it visually.