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DTC codes / BMW codes / P1690

P1690 · BMWMalfunction Indicator Lamp MIL Electrical

P1690 on BMW vehicles indicates that the engine control module (DME) has detected an electrical fault in the circuit that drives the Malfunction Indicator Lamp (MIL), which is the check engine light on the instrument cluster. The DME monitors the MIL output for open circuits, short circuits, or excessive current draw, and sets this code when the expected electrical behavior is not present.

SystemPowertrain
Code typeBMW specific
SeverityLow
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • The check engine light may not illuminate at all when the ignition is turned on, failing the bulb check.
  • The check engine light may stay illuminated constantly even when no other faults are present.
  • Other stored fault codes may be present but the MIL fails to illuminate as required.
  • The instrument cluster may show a bulb failure message or the MIL may flicker intermittently.
  • Often no symptoms besides the warning light itself, especially if the fault is intermittent.
  • In some cases, the engine may run normally with no drivability issues, as the MIL circuit is separate from engine management.

Common causes, most likely first

  1. Failed or burned-out MIL bulb in the instrument cluster.
  2. Open or short circuit in the wiring between the DME and the instrument cluster MIL circuit.
  3. Corroded or loose connector pins at the DME or cluster harness.
  4. Faulty instrument cluster internal circuitry affecting the MIL driver.
  5. Defective DME output driver for the MIL circuit.
  6. Water intrusion or damage to the wiring harness causing intermittent shorts.
  7. Aftermarket alarm or remote start installation tapping into the MIL circuit incorrectly.

How to diagnose and fix it

  1. Verify the MIL bulb illuminates during the instrument cluster self-test with a scan tool or by cycling the ignition.
  2. Check for other stored fault codes that might indicate a related circuit issue.
  3. Inspect the wiring harness and connectors between the DME and instrument cluster for damage or corrosion.
  4. Test the MIL circuit for continuity and short to ground or power using a multimeter.
  5. If the bulb is faulty, replace the instrument cluster bulb or repair the cluster as needed.
  6. If wiring is faulty, repair the open or short circuit and clear the code.
  7. If the DME driver is faulty, replace or reprogram the DME as a last resort.

MIL Circuit Faults Often Misdiagnosed

  • A common mistake is replacing the instrument cluster when the actual fault is a simple open circuit in the wiring harness near the DME connector.
  • The MIL circuit is monitored by the DME only when the ignition is on and the engine is not running, so intermittent faults may not set the code during normal driving.
  • Aftermarket electrical accessories wired into the cluster can backfeed the MIL circuit and cause this code without any factory component failure.
  • On some BMW models, a weak battery or voltage drop can cause the DME to falsely detect a MIL circuit fault, so always check battery condition first.
  • This code does not affect engine performance directly, but it can mask other emissions-related faults because the MIL may not illuminate when needed.

Can I keep driving with P1690?

The vehicle is generally safe to drive because the MIL circuit fault does not affect engine operation, but you should avoid long trips until the issue is repaired. The main risk is that the check engine light may not illuminate for other serious faults, potentially leading to undetected emissions or engine problems.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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