I know this has been discussed thoroughly on other forums but I haven't seen an in-depth discussion on this forum so here goes. Car is a 2007 Z4M Coupe (E86M) its symptoms are - first radio audio cuts off, then ABS, DSC, and Brake lights flash on and off at times it feels like the brakes are being gently applied. If they stay off long enough the radio audio comes back on. Obvious candidates are Stability Control Module and/or speed sensors. Other forums suggest bad battery or faulty voltage regulator. My diagnosis started with measuring battery voltage with the car off. At battery terminals voltage was 11.5 volts - ah ha low. Started car to check alternator and voltage regulator, voltage at batter was 14.2 volts at idle and at 4,000 RPM, turned on A/C and lights, voltage at battery dropped to 14.18 volts at idle and 4,000 RPM - concluded alternator and voltage regulator are working properly. Connected battery to Battery Minder for 5 - 7 days, Battery minder indicator lights show battery is fully charged. Connected Bavarian Technic OBD II diagnostic cable and software (version 1.9.4.0) to car, to read Fault Codes, DSC module showed code 5E16 - can't clear fault. Test drove car with no indicator lights (test drive was about 12 miles with no restart of engine), battery minder was reconnected to battery. Next day test drove car 5 miles with no indicator lights, turned engine off and restarted engine, got indicator lights after 1 - 2 miles. Multimeter showed 12.5 volts at battery terminals. Talked to Bavarian Technics they suggested I check instrument cluster for fault codes, check show a couple of codes that all cleared. All were electrical in nature. Changed battery today finding light corrosion on the positive terminal, and test drove car. After 7 miles (about 10 minutes) with no engine restart symptoms appeared. Connected the Bavarian Technic cable to the car to check fault codes, the following codes appeared: 1. Engine - Fault code 2E7C Bitserial data interface, signal Error will not cause a warning light Error is not currently present Test condition have been completed Time out Was able to clear code 2. Dynamic Stability Control DSC Fault Code 5E16 DSC-ECU-internal: Failure Processing System Transfer Error. SP-interface timeout in System- Server Error will not cause a warning light Error is not currently present Test conditions have been completed Code will not clear 3. Steering Angle Fault Code 9 Not an ASC2 Message Was able to clear 4. Electronic Immobilise System 3 (EWS3) Fault Code 15 Power on reset Was able to clear All codes were read with the ignition key and emergency flashers on, battery minder connected, and engine off. Do these codes point to a speed sensor or Stability Control Module? Taking clues from the Hack Mechanic's recent article on this Z3 DSC my next step is to look for chassis ground issues but I've no idea if the Radio and DSC share a common ground point; in fact I have a hard time believing it. If the DSC fails does it cut power to the radio amplifier? If I am reduced to swapping parts with new parts until the problem goes away my next step is the Speed sensors, I saw on Pelican Parts web site the Delphi sensors were about 1/4 the price of BMW labeled sensors and ATE sensor were 1/2 BMW price. Does anyone have experience with Delphi or ATE. sensors? Lastly, I can't rule out a defective new battery; however, that is sort of immaterial as I plan to reinstall the old (4 years) battery tomorrow and return the new battery (AutoZone). Appreciate any help I can get and promise to post the final results when I get the problem fixed.
When you checked the battery voltage with the lights on you said you got 12.5v was that with the engine on or off? Sounds like some sort of voltage regulation issue. Either it is spiking to high and the the computers are shutting down to prevent damage. Or there isn't enough output from the alternator and the modules shut off to save power. The steering angle sensor fault could also cause the lights to come on but not the radio issue.
Thanks for the help. The 12.5 volt reading was with the engine off. Had the original battery tested today, this was an 1 hour load test at our local Ford dealer, it checked good. Did I mention this is a small town about an hour from the nearest BMW shop. Is their a way to check the alternator/regulator in a home shop or do we need a computer?
You could use a multi meter that has a min max button on it. You will hook it up to the battery positive and negative and then drive until the lights come on. In the min max button will record the highs and lows of the voltages it measures. Once the lights come on check the meter for it's high and low and see if there is a problem.
OK finally able to jury rig a test setup and measure voltage across at the battery terminals while driving - this did require a passenger to hold and read the digital multi-meter. Pretty interesting results - all of which indicate a new voltage regulator is required. While cranking the engine voltage dropped to 10 volts quickly recovering to 14.2 V as the alternator came online, while I've never measured this before I suspect this is normal behavior. As we backed out of the garage the voltage jumped to 15 volts then settled back to 14.2 V. Shortly after hitting the street drive the radio cut out and theall three warning lights flashed on and went off, multi-meter read 18.+ volts for an instant. Voltage then settled to 14.2 volts. As the drive continued we noticed the voltage gradually climbed to a steady 14.89 volts spiking to 15 volts when changing gears. Unfortunately, the three warning lights only came on for an instant once more during this test drive and other than the single 18 v spike the meter never went over 15.2 volts. Our conclusions are the voltage regulator is indeed bad. I suspect the reason the symptoms weren't as frequent or severe during this drive as during previous tests is the ambient temperature is 81 degs today rather than 95 degs. As soon as the engine cools I'll put the alternator to get a part number for the voltage regulator. Hopefully, I'll be able to find the regulator sold independently of the alternator online. I want to thank you for your help and will add a post if the regulator cures the problem.
Glad you figured it out, personally I would get the alternator rebuilt while your replacing the regulator anyway so you can have the bearings replaced.
As promised here is the final chapter of this saga. Replacement alternator arrived today, this is a good story in itself. I got it installed this afternoon and took the car on a post repair test drive. Since the problem had been intermittent I decided to replicate the alternator test just to see if any conclusions could be drawn from voltage tests. First the good news, 30 mile test drive, air temperature in the high nineties, no indicator lights. Even purposefully triggered the DSC, only the DSC light flickered and immediately turn off when traction returned to the rear tires (normal operation). As to the voltage test, max voltage observed during the drive was 14.3 - I believe the problem is solved. If it returns after more driving I'll be back. The alternator story, I checked with a BMW dealer in the region, they wanted $780, before a discount, for a remanufactured alternator. A BMWCCA member discount was reluctantly agreed too; another BMW source wanted $600+ for a remanufactured unit. These prices spurred a further internet search for an OEM alternator, I found a remanufactured Valeo unit advertised for $200. When I called to order I was told they didn't have a remanufactured unit in stock but had a new Valeo alternator for $300 with free shipping - came with a 1 year warranty from Valeo. Parts numbers on the new unit matched the numbers on the unit I took off the car. I want to thank Charlson89 for quick responses and his solid advice to this forum, and the Hack Mechanic for inspiring me to get my hands dirty and seeing this problem through to the end. My membership renewal is in the mail. Thanks guys.
