P0899
Transmission Control System MIL Request Circuit High
Transmission / MIL request circuit
Generic OBD-II
Low
What it means
P0899 means the circuit the transmission module uses to request the check-engine light is reading high — often a short to voltage or a wiring fault on that line. The engine still starts and runs, and this code by itself rarely affects shifting, but you should read any companion transmission codes, since the fault that prompted the MIL request can be the real concern.
Low
Can I keep driving? Usually driveable with no direct shifting problem, but check for any companion transmission codes that could be more serious.
Common symptoms
What you'll notice
- Check-engine light on (or stuck on)
- MIL won't turn off even after codes are cleared
- Reduced or no communication with the TCM on a scan tool
- Companion transmission codes may also be stored
Common causes
Most likely first
- Short to voltage in the MIL request circuitLikely
- Wiring or connector fault between the TCM and instrument clusterCommon
- Faulty transmission control moduleCommon
- Instrument cluster or related component faultLess often
How to diagnose & fix
Work through it in order
- Read all stored codes first — address any real transmission faults that triggered the request.
- Inspect the MIL request wiring between the TCM and cluster for a short to voltage or damage.
- Check connectors at both ends for corrosion or loose pins.
- Verify TCM communication with a scan tool; repair wiring before condemning the module.
- If wiring and cluster check out, diagnose the TCM.
FAQ
Quick answers
Is it safe to drive with P0899?+
This code by itself is mainly a warning-light circuit issue, so driving is usually fine — but read the other stored codes, as the underlying transmission fault matters more.
Can I just clear P0899?+
If the circuit is shorted or a real fault remains, the light comes back. Fix the cause rather than just clearing it.
Related codes
Often seen with P0899
Read & clear P0899 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX