I can only assume; that the new key is not "matched"; to the immobilizer, thats why your old key doesn't cause the light to flash (the immobilizer "sees" the transponder chip and it is programmed/matched into coding of the speedo/immobilizer chip/ecu). You might take your "new" key fob apart and see if there is a transponder chip in there; many of the replacements don't . You could get a new chip and use vcds to add it to the car: key matching. Your car starts; because the immo is deleted in the ecm but that doesn't deal with the fact that the new key isn't adapted/matched to your immobilizer (even though it is "deleted" or "defeated"); maybe Malone Tuning can explain how the eliminated immo feature works and how it does/doesn't interact with the system. As it is; the immo system is intact and it can see the transponder with the reader coil etc.
Watch this video:
This seems to explain the flashing light issue; even when you have a tuner "delete" the immo:
Immobilizer Delete For many VW and Audi cars
kermatdi.com offers an immobilizer delete service for all VW/Audi (VAG) cars. This requires sending the ECU to our service center.
Most ECU's are $155 although some ECU's may require an extra charge
Q: How can I tell If I have an immobilizer problem?
A: If your car will start and run, but shuts off immediately, with the "car in key" symbol lit on the dashboard, then you may have a faulty immobilizer. An immobilizer delete may help. Please see the demonstration in the video below. The antitheft provision of the immobilizer shuts off the engine if the car is started without a matched ignition key. (or if there is a problem with the immobilizer system itself) There should be a fault code stored in the ECU (P1570 or 17978 fault code indicates "Engine start blocked by immobilizer")
Q: My car doesn't run! Isn't this always caused by the immobilizer?
A: No. If the car does not start and run at all, then it’s NOT caused by the immobilizer. If the car runs for a few minutes then stalls out while driving, it is NOT caused by the immobilizer. If the car runs rough, or misses and stalls, then it is NOT caused by the immobilizer. Likewise, deleting the immobilizer will not help if the no-start is caused by something like a dead battery, out of gas, or some other mechanical problem.
Please note: If the car does not start and run at all, then it’s NOT immobilizer related. Deleting the immobilizer will NOT help if the no-start is caused by something like a dead battery, out of gas, or some other mechanical problem.
What is an immobilizer?
All VW and Audio cars since about model year 2000 include a factory anti-theft system. This anti-theft system includes something called an immobilizer, or "immo" for short. When it’s working properly, the immobilizer allows the engine to run if the correct key is used to start the car. However, a malfunctioning immo makes a car undriveable, because the car shuts off right after it's started! With a bad immobilizer, the engine WILL START, but NOT STAY RUNNING for more than a second or two after starting.
Fortunately there is something called an immo bypass, otherwise known as an immobilizer "delete". This reprograms the Engine Control Unit (ECU) immobilizer function, so the ECU ignores the faulty immo. With the immo deleted, the car will run independent of the immobilizer, even if the immobilizer itself is defective. As their VW and Audi cars age, many car owners welcome this immo delete, which allows them to drive their car when the immobilizer is broken.
Other reasons to delete the immobilizer:
Sometimes you lose a car key, or need to make an extra key for your car. These will also trigger the immobilizer, and the car won't run. Reprogramming at the dealer can be expensive or inconvenient.
Immobilizer delete lets you add a remote start feature from an aftermarket security system. Otherwise the immobilizer will prevent the car from running without the special key in the ignition, which kind of defeats the purpose of a remote starter.
ECU goes bad and you wish to replace it with a less expensive used ecu (We can duplicate the data in your existing ecu over to the replacement in this case if desired)
Well, how does an immobilizer actually work? It goes something like this:
Shortly after the engine starts, the engine computer asks for the "ok" from the immobilizer module (which is physically located in the insturment cluster).
The instrument cluster looks for the presence of the "chip" in the ignition key, through an antenna in the steering column.
If the signal from the key is detected, the instrument cluster tells the ECU "ok keep running"
If the signal from the key is not detected, the instrument cluster tells the ECU "not ok" and the ECU shuts off the engine. The instrument cluster illuminates the "car in key" lamp to indicate an immo problem, and a fault code gets stored in the ECU.
The immobilizer has at least two components: The engine computer and the module in the dashboard. Sometimes there is an alarm system, which is the comfort and convenience module (door locks, flashing lights, etc.) The instrument cluster has an antenna that detects the transponder "chip" in the ignition key. With an immobilizer delete, the Engine Computer doesn't ask the instrument cluster about the immobilizer. In other words, the car with a faulty immobilizer will still start and run - with an immobilizer delete.
>>>>>>>>>> PLEASE NOTE: it's important to emphasize, not all "no-start" issues are immobilizer related. There are a number of reasons why a car won't start!. If it's the immo, the "car key" light will be flashing in the instrument cluster. The car will start, run for 2 seconds and then shut off again. There will be "immobilizer fault" codes stored in the ECU memory when scanned with an OBD code reader. For VW this code is described as:
17978 - Engine Start Blocked by Immobilizer
P1570 - 008 - - Intermittent
What about the flashing light? While the car will run normally again, an engine immobilizer bypass won't always fix all the other symptoms of a faulty immobilizer caused by one of the other components. For example, the dashboard light may still blink, if the immobilizer problem was caused by a broken antenna pickup, or a broken transponder chip in the ignition key. This is because the actual immobilizer function is NOT in the engine computer, it is in the dashboard. Immo delete separates the dashboard function from the ECU. In other words, although the engine controller ignores the immo input from the instrument cluster, the immobilizer in the instrument cluster may continue to complain with a flashing dash light. However, at this point, the flashing dash light is of no functional consequence. It is merely a nuisance once the immo is gone from the ECU. The answer to a flashing immobilizer warning light in the dash after immo bypass, is simply to physically remove the light bulb from the dash!
kermatdi.com offers an immobilizer delete service for all VW/Audi (VAG) cars. This service requires removing the ecu from the car, and sending the ECU to our service center for the repair. Please feel welcome to call or e-mail us with any questions!