BMW · DTC LOOKUP
CAS4/CAS4+ ISN mismatch — BMW F/E-chassis CAS4 ISN doesn't match DME
BMW diagnostic code. Below: what it means, common causes, symptoms, and the exact bench-programming fix path.
Common causes
- •Donor CAS4 installed
- •Donor DME installed
- •Failed coding rewrite
- •Battery drop during ISN write
Symptoms you'll see
- •Crank-no-start
- •CAS-DME comm fault
- •Existing keys rejected
The fix path
Ship CAS4 + DME together. BMW CAS Key Programming ($150) reads DME ISN, writes to CAS, pairs keys.
AML services that fix this
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Related diagnostic codes
P1570Engine Start Blocked by ImmobilizerP0513Incorrect Immobilizer KeyFRM/FRM3 not detectedBMW FRM/FRM3 Footwell Module unresponsiveEWS-DME comm errorEWS module not authenticating with DMECAS-DME comm errorCAS module unable to authorize startBMW E46 cluster pixel lossBMW E38/E39/E46 instrument cluster pixel dropoutsNot sure which service applies?
Text us your year/make/model + which scanner caught the code — we'll tell you exactly which module to ship and which service to pick.