100$ bounty to find my check engine light

[BurntSoup]

Okay ladies and gents I'm still in the midst of this atw to awm swap and trying to get this car to start for the first time. I'm at the point where the engine swap itself is done. I however have not been able to get the dash to communicate with the ecu. Pertinent information is as follows.

• I never performed the adaptation on the dash originally. By the time I had gotten my vagcom I was midway thru the swap and did not know how I would get the new motor to start as the final step with the old electronics
• The dash would show a check engine light with the old harness and old ecu but not with the new harness and old ecu
• got it to crank twice after this but never again so far, idk if that's a bad crankshaft position sensor or what, ignition also locks after a crank and you have to turn it back to off befoe trying to crank it again don't know if that's relevant or not
• I chopped the old harness apart after discovering the new harness had been tweaked and someone had wired up the plug for the ecu relay very very wrong, simply soldered the plug from the old harness onto the new one so the relay wouldn't short, this made the bad relay code on my vcds disappear but still no cel
• became convinced it was because of the plugs between the ecu and the cluster, soldered those from the old harness to the new and pinned the missing terminal wires into the ecu plug
• still no cel
• got an awm passat harness from my nearest junkyard, still no cel
• put the project down for about a month, then traveled 3 hours to the nearest junkyard with a 2001 a4, pulled the instrument cluster, ecu, and wiring harness all from the same awm a4 and swapped those into the car thinking this would have to work
• still no cel

which brings us to where we are now. The only ideas I have left are to go pull an atw harness and then using the passat harness as a donor and change the plugs to try and get it to start for the final step of the adaptation, or pay one of you folks much more experienced with this platform than me to figure out this puzzle. 100 usd payable however you would like to the first person to get my check engine light to come on.

[rzyao]

You shouldn't have to deal with immobilizer stuff because the B5 never came with those here in America. I'm thinking you might have a bad ECU relay, which would cause it to not turn on. What I would do is: Check for voltage on the voltage input pin of the relay socket; it should have positive voltage. Also, see if the relay is clicking or not. Sometimes they just fail and cause a no start issue, and it seems to be a consistent part that was never ruled out. I would also check the voltage pins of the ECU harness and see if it's getting the appropriate on voltages. I think what you could do is check pins 3, 21, and 62 and then see if they're getting voltage (very carefully!!) as those should be enough to "turn on" the ECU. After that, the wiring should be mostly straightforward. This should at least tell you what's happening or not happening. If no ECU power, follow the wiring diagram/harness to see where the power is cut off. If power to ECU, see if the connections between the cluster and the ECU are bad.

Regarding the no-crank, you likely have either a bad clutch switch, a bad ignition switch, or a bad engine ground. If you jump the ignition switch, what happens? They can go out sometimes causing a no-crank situation.

[rzyao]

About the key position, that's completely normal. I assume it's to prevent you from bumping the starter while the engine is running, but I've always had to turn the key off to crank again if I stalled or something

I assume you've already done this, but check the fuses with a meter to be safe and rule that out too, especially all of the electronics in the ECU box.

[walky_talky20]

I second the ECU Power Supply Relay. That is where I would focus my testing at first.