I'm brand new to this forum, but I need some help! I have a 2012 BMW z4 sDrive28i 2.0L Turbo, and I have been getting the following fault codes 280F, 28A1, and 2C57. I have replaced all of the air intake pipes or tubing, replace the gasket for the lower air intake that connects to the turbo, new alternator, new MAF and MAP sensors, and a brand new intercooler, I've done a smoke test under pressure to check for leaks and their are none, yet I'm still getting these codes AFTER I drive the car until it heats up normally, and once I let it sit for 5 to 10 minutes, I get those 3 fault codes on my code reader. Could someone point me in the direction to fix these codes, because I'm at a loss to try and figure this out! Thank you guys, and by the way I love this forum!
Frustrated with Fault Codes
- Thread starter David B
- Start date
Welcome to the forum David, and sorry to hear you are having problems, all 3 fault codes refer to different problems and the only thing I can think of that would give all 3 under the circumstances you described is a faulty battery, the E89 is very fussy when it comes to voltage, have you had it replaced at any time? If you look on the negative terminal (could be positive, can’t remember) it should have a date stamp on the top, week/year of manufacture, eg 08/12, the middle of February 2012.
If they aren’t related then 280f, possibly a faulty o2 sensor,280A1 could be a faulty battery charging monitoring module, 2c57 waist gate fault on the turbo?
I’m no mechanic and only my best guess I’m afraid but hope it helps or perhaps someone else may know better.
If they aren’t related then 280f, possibly a faulty o2 sensor,280A1 could be a faulty battery charging monitoring module, 2c57 waist gate fault on the turbo?
I’m no mechanic and only my best guess I’m afraid but hope it helps or perhaps someone else may know better.
Scottish Borders
raymond.harper
Senior member
Battery voltage should be over 12.5. 11 volts is not enough to start the car. It could be that there is a parasitic draw on the battery. Take a voltage reading when you finish driving the car, and then another the next day before you start the car to test for a draw.
Personally in this case I doubt its battery related..but best to check..FWIW voltage on car running can vary between 11 ish and 14.7..just charge it up via the charge pole..that's the simplest way..clear error codes and revisit.. on the N54 similar faults were either vacuum or boost leaks almost always
I want to apologize for not getting back to those that answered my post, but I had a weeks vacation and now I'm back home! I tested my battery and it read 12.23 volts and its a DURACELL PLATINUM AGM battery with 850 CCA actual part number 49(H8)AGM. And it's been sitting for over 10 days without the car being used.
By 'tested' do you mean you put a multimeter across it? That's a tiny bit better than worthless TBH.
Actual battery testers are cheap on amazon - a voltmeter reading tells you very little about whether you have a battery issue.
You need to see what's happening when the battery is under load, very hard to do without an actual battery tester.
Actual battery testers are cheap on amazon - a voltmeter reading tells you very little about whether you have a battery issue.
You need to see what's happening when the battery is under load, very hard to do without an actual battery tester.
Have you asked ChatGPT?
I just did - answer below.
There’s a high chance that the codes are tied together because of voltage instability or CAN-bus communication issues. Low or fluctuating voltage can cause the DSC module to miscommunicate, mislead pressure sensors, and flag boost control as failing—even if physically, everything seems sound.
** What to check next (mentor-style):**
I just did - answer below.
There’s a high chance that the codes are tied together because of voltage instability or CAN-bus communication issues. Low or fluctuating voltage can cause the DSC module to miscommunicate, mislead pressure sensors, and flag boost control as failing—even if physically, everything seems sound.
** What to check next (mentor-style):**
| Step | Action |
|---|---|
| 1 | Battery & Voltage Stability – Use an actual battery tester to check resting and running voltage. Should be stable above 12.5 V. Look for parasitic draws or signs of battery weakness. |
| 2 | CAN Communication – Scan for DSC-related faults or bus errors. Re-seat connectors, inspect wiring, especially around the DSC module and DME. |
| 3 | Boost System Review – Check the wastegate actuator, vacuum lines, pressure converter (vacuum pressure modulator), and clamps again—even if you’ve smoke-tested before. Forums often point to these components.Z4-forum |
| 4 | Sensor Check – Intake pressure sensors or ambient sensors may be on the fritz—test or swap to confirm. |
| 5 | Clear and Monitor – After any repair or test, clear the codes and drive it. Some codes may only appear once the engine is hot or during cooldown. That’s a clue in itself. |
I added the info about the codes only coming back after a drive 7 the car cools (again - chat GPT response below):
That’s a useful clue — the fact the codes only return after a drive and cooldown points away from constant hardware failure and more toward a heat-soak then cool-down electrical or vacuum issue.
Here’s why:
That’s a useful clue — the fact the codes only return after a drive and cooldown points away from constant hardware failure and more toward a heat-soak then cool-down electrical or vacuum issue.
Here’s why:
- Heat expansion/contraction can open up small cracks in wiring insulation or cause micro-fractures in solder joints, especially in sensor connectors or the DME (ECU).
- When the engine cools, condensation can form in connectors, particularly around the boost pressure sensor, MAP sensor, or DSC wiring.
- Vacuum leaks from rubber hoses can seal when warm but open slightly when cold, triggering the 2C57 “boost too low” fault on the next start.
- Weak batteries or alternators often test “fine” warm, but after shutdown and cooling, internal resistance changes and voltage dips trigger CAN and plausibility errors.
- Wastegate actuator or vacuum leak that changes behaviour as the turbo hardware cools.
- MAP / boost pressure sensor starting to fail under heat cycles.
- Battery/charging system giving unstable voltage after shutdown → can cause 280F & 28A1 to reappear.
- Connector or wiring issue that only loses good contact when cold again.
- After a run, park the car, let it cool until the codes would normally appear, but before starting it, measure battery voltage. Anything under ~12.4 V is suspicious.
- Wiggle-test connectors to the boost sensor, MAP, and DSC module when cold. If moving them causes a brief voltage change or code appearance, you’ve found the culprit.
- If you have access to a smoke machine, test the boost/vacuum lines when cold, not warm.
- Consider logging boost target vs actual in ISTA or a BMW-capable scan tool during the next drive — if actual boost is fine warm but drops after cool-down start, that’s very telling.
What about your positive crankcase ventilation valve not working?
Or turbo waste gate leaking?
Chat gpt says:
“
A bad PCV is more likely to be the root cause if:
Or turbo waste gate leaking?
Chat gpt says:
“
A bad PCV is more likely to be the root cause if:
- There’s oil residue in the charge pipes or intercooler
- You hear a whistling noise at idle
- Removing the oil cap at idle is difficult (excessive vacuum)
- There are rough idle, long cranks, or oil consumption issues
- A smoke test shows leaks near the valve cover”
Well, I'm back! We replaced the plastic BMW valve cover with a New Aluminum one, AND we replaced the lower pipe that runs between the two sensors. I thought we had it FIXED but NOPE, the fault code P12A4 is still popping up. I have replaced every sensor on this car so I don't get it. A mechanic friend suggest I re-calibrate the software with ISTA-P software from a BMW dealership because he said the P12A4 fault code is a ghost code but I am reluctant to try this. I also have seen FREE ISTA + and ISTA-P software on the internet but some folks say use only BMW certified software. ANY RECOMMENDATIONS???
You haven’t mentioned the P12A4 code before, so is this a new code after you have been replacing parts?
Was the replacement MAP sensor a genuine one?
I’ve got ISTA+ and not had any issues with it but not used ISTA P yet for coding (I’m a little hesitant to install it with having ISTA+ already on my laptop, if I ever reinstall windows then I may add ISTA P)
Was the replacement MAP sensor a genuine one?
I’ve got ISTA+ and not had any issues with it but not used ISTA P yet for coding (I’m a little hesitant to install it with having ISTA+ already on my laptop, if I ever reinstall windows then I may add ISTA P)
I bought ISTA+ from eBay over 5 years ago, it came as a package with the OBD11 cable and a collection of other software NCSExpert etc and only recently downloaded ISTA P, all the software is available to download for free if you can find it, there’s often links on other forums.