BMW E65 735i - 2003 (N62 32 valve - V8 engine)

Data Bus error tells me it's a problem with the ECU communicating with the VVT system. "no signal' also says the same thing.

Look for broken wiring. Look for loose connectors. Look for frayed wires at the connectors. Look for contaminated connections and connectors. Anything that can keep the system from communicating with its component parts.

Do you mean the VVT ECU or the main engine management ECU? Thanks.

Both. Check the VVT controller first. Then move to the main ECU.

Thanks. The only time the wiring has been disturbed was when the VVT ECU was replaced and the car has been running fine since then for 10,000 miles. I'll check all the wiring and clean all the connector blocks with an electrical cleaner aerosol.

Ok. Let us know if that makes any difference and we'll go from there.

Thanks - I won't get a chance to do it until after the Christmas Holiday but I will let you know how it goes. Happy Holidays!

Ok. Festive Yule. Look forward to hearing back from you.

Thanks. The problem hasn't re-occurred for the last few days but I will still carry out an 'inspection and clean' as soon as I can and get back to you.

I have asked a separate question with another donation. I don't know if it will get to you or another expert. I am new to the '2CarPros' website and assumed that new questions had to be posted separately.

It is appreciated whn they do. Most likely another expert will grab it.

Or not.

DrCranknWrench got it.
How is this one running Gtemco?

Hi Again - I thought I would update you on the problem.

After a period of unseasonably mild weather during which time the problem didn't re-occur, I went into the electronics box and checked the wiring and connectors (no visible problems found); I removed the valvetronic ECU, main DME ECU & Integrated Supply Module and cleaned all of the connectors with electrical contact aerosol spray. After re-assembly and power up the car ran fine for a few days. Then after the car had been left standing for a few days during a particularly cold weather period, the problem returned with a vengeance with the car going into 'Limp Home' mode. Not only am I getting the same P1065 code. I am now getting a related P1061 code 'Variable Valve Timing, Bank 1 - Limp Home - circuit malfunction'. In addition I am getting other failure messages from the DME, e.g. 'ACC Failure - drive with caution' - 'DSC Failure - drive with caution'.

I am now beginning to suspect the main DME ECU and the fact that the problem seems to be temperature critical. Note:- 1. The original problem back in December started after the car had been left standing in very cold weather and disappeared when, for a few days, the weather became very mild. 2. When the temperature under the hood is raised after 10 - 15 minutes of the engine running, then I can switch the engine off, wait for a minute, re-start the engine and the problem disappears (almost like doing a 'warm re-boot' on a computer) 3. The problem only returns after the car has been left standing in low temperatures (overnight in this case). 4. During problem periods I notice a slight 'roughness' in the engine's running and when I detect a definite 'smoothing out' in the engine, I know that's the time to pull over and perform the 'warm re-boot' previously described, confident that the problem won't re-occur for that driving session.

As you know from earlier in this thread, the car is running a valvetronic ECU from a donor vehicle and ran for 10,000 miles with no problem. Could I install the main DME ECU from the same donor vehicle (identical model and year)? or would data conflicts prevent it from running? Hell.........p!

PS. I was almost at the point of giving up on this car and scrapping it but the 'mule' in me has picked up the gauntlet, determined(for now anyway)not to be beaten. Another donation to this great website is on it's way.

Go ahead and give the donor car ECU a try. Remember that it will take awhile to "get used to" the conditions and sensors in the car.