BMW 3131 — Vehicle Mode Message Checksum Error
- Severity
- Informational
- Module
- DME
- OBD-II Code
- U1116
Description
Fault 3131 (U1116) is logged by the DME when it receives the CAN message for "vehicle mode" (message ID 0x315) but the payload fails its checksum validation. The vehicle mode message carries state information from the centre console button block or junction box — most notably Sport/Power button status on equipped vehicles. The transmitting module varies by platform (SZM, JBBF, GWS, or ZGW depending on chassis). The DME needs this information to adjust throttle mapping, shift behaviour (on auto-trans cars), and related drivetrain responses. A checksum error means data is reaching the DME but arriving corrupted.
The DME is receiving message 0x315 but the running counter or CRC does not match the expected value. This is different from a missing message (see fault 3132) — the bus is active and the sender is alive, but the data is being corrupted somewhere between transmitter and receiver.
3131 - U1116: Vehicle Mode Message Checksum Error - Checksum error
Symptoms
Often no driver-visible symptom. On vehicles equipped with a Sport/Power button, the button may not consistently change driving mode. This fault is most commonly discovered during a routine scan or when investigating other faults. Brief, self-clearing events (a stored but not currently present fault) frequently trace back to a marginal battery or a voltage dip during cranking.
Common Causes
Ranked by frequency:
- Low or degraded battery causing voltage dips during cranking (most common)
- Corrupted bus traffic from a third module on the same CAN segment — frequently a module elsewhere in the network intermittently flooding the bus
- Damaged or chafed CAN wiring causing intermittent bit errors
- Poor ground connection at DME or at the transmitter module
- Failing CAN transceiver on the sending module
Diagnosis Steps
- Read fault memory on all modules, not just DME. Checksum errors are often a symptom of a larger bus problem — another module may be the actual cause.
- Test battery open-circuit voltage, load-test the battery, and check the charging system. Anything below 12.4 V resting voltage is suspect. Replace and register the battery before chasing wiring.
- Check for other U-codes stored concurrently on DME and elsewhere. A cluster of U-codes pointing at the same transmitter is a strong diagnostic clue.
- Measure CAN bus resistance with the battery disconnected. ISTA specifies 60 ohms (two 120-ohm termination resistors in parallel). A reading of 120 ohms indicates one termination is missing; anything below ~55 ohms suggests a short or added load.
- If the fault is persistent and isolated to DME, inspect wiring at the DME connector and at the suspected transmitter — look for chafing, corrosion, and pin fretting.
Resolution
Address the root cause identified in diagnosis:
- Battery/charging issue → replace battery, register it, retest
- Faults on another module → repair that module first, then re-scan
- Wiring damage → repair the harness; do not attempt soldering unless you are equipped for a proper inline repair
- Defective transmitter module → replace (requires programming and coding to VIN; refer to RealOEM or ETK for part selection by VIN) After any repair, clear all fault memories and perform a short drive cycle, then re-scan.