Skip the auto shop - Our mechanics make house calls

Q: BMW E39 has no response

asked by on

I have a problem. BMW E39 has no response. I've tried to scan it with my diagnostic tool. I can't scan it at all. The box is in safe mode. I expect the ECU is bad but I'd like to know your opinion.

Yes, it probably is the main computer. It’s a really common problem. If you can’t get any response from the scan tool, there are really only three things that can go wrong: the main computer could be bad, the wiring between the main computer and the sensor in your data port could be shorted out, or you’ve got a bad sensor that shorted the whole thing out.

Rather than start with buying a brand new computer, my advice is to go through each of the sensors in the car with the key turned on, and unplug them one at the time. When you unplug one of them and suddenly the scanner can diagnose and start getting data from the computer, this will mean that a sensor is bad. In this case you’ll need to replace that sensor first. This is how I test them so you will want to try it out and fix that first, rather than buying an expensive new compressor or a new ECU on a guess.

You don’t want to guess with something that expensive. I’d recommend having a certified technician diagnose why you’re car is not responding and make any necessary repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car stopped

Hello. I will try to assist you. A car that "suddenly" stops operating with no sound is preferred to one that stops suddenly accompanied by an unusual "noise". The former cases are almost invariably due to a sudden fuel, ignition,...

Q: When you start off it bogs down and then takes off?

This sounds like potentially a fuel delivery or air regulation problem. There is a sensor in your truck called a mass air flow sensor which regulates the flow of air into the engine allowing for the proper air/fuel mixture to...

Q: belts could not be changed because they couldn't not be removed by mechanic

Nissan and Infiniti vehicles usually require you to adjust two different bolts to remove the belt. The two bolts are the lock bolt and the adjustment bolt. These bolts are usually located on the power steering pump or the alternator....

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.