2012 BMW X5 N55 Engine Cranks But Won't Start - No Codes Found
2012 bmw x5 with a n55 engine. Crank no start. I checked all the fuses, all good. There are no codes. The fuel pressure is good lownpressure and high pressure fuel pump. Injectors get up to 90v when i crank so that circuit is goood, i tried to spray starting fluid into the i take but nothing happened didnt even try to start.
You’ve got a crank/no start, no codes, fuel pressure is good, injectors are firing, and starting fluid does nothing. That points hard at a no spark situation. On these N55s, if you have fuel and compression but it won’t even cough on ether, spark is dead or way out of sync.
Most likely culprit is a loss of ignition spark — either all coils aren’t firing, or the DME isn’t commanding them due to a missing crank signal. Crank sensor failure is common and can cause a no-code, no-start if it drops out completely. DME failure is possible but rare.
Most likely culprits
- No spark at all cylinders — fits the “no start on ether” and no codes.
- Crankshaft position sensor failure — if the DME can’t see engine position, it won’t trigger spark or fuel.
- DME not seeing crank signal — could be wiring, sensor, or rarely the DME itself.
How to narrow it down
-
Check for RPM signal during cranking
Watch live data on your scan tool. If RPM stays at zero, crank sensor or wiring is dead. If you see RPM, move to step 2. -
Test for spark at a coil
Pull a coil, stick a plug in it, ground the plug, crank. No spark = ignition system issue. If you get spark, you’ve got a timing or mechanical issue. -
Check crank sensor wiring and connector
Look for oil intrusion, broken wires, or corrosion at the sensor plug. -
Scope the crank sensor if you have access
No waveform = dead sensor. Good waveform but no RPM on scan tool = wiring or DME issue. -
Compression check
If you have spark and fuel but still no start, check for zero compression (timing chain slipped, but that’s rare without noise).
Possible parts (if needed)
- Ignition coil set (if no spark at any cylinder)
- Crankshaft position sensor (if no RPM signal or bad waveform)
A few questions
- When you crank, does the tach needle move at all?
- Have you checked for spark at the plugs during cranking?
- Any recent work, oil leaks, or water intrusion around the engine harness or DME?
Let me know what you find on the RPM signal and spark check — that’ll pin it down fast.