P0804
Upshift/Skip Shift Lamp Control Circuit
Transmission
Generic OBD-II
Low
What it means
P0804 means there is an electrical fault in the circuit that drives the upshift (skip shift) indicator lamp — the light that tells a manual-transmission driver to skip a gear for fuel economy. It affects only the lamp, not how the engine or transmission performs. Typical causes are a burnt-out bulb or a wiring or connector fault in the lamp circuit.
Low
Can I keep driving? Fully drivable — this affects only the skip-shift (upshift) indicator lamp, not how the car runs or shifts.
Common symptoms
What you'll notice
- Upshift (skip shift) indicator lamp does not light, stays on, or behaves erratically
- Check-engine light on
Common causes
Most likely first
- Burnt-out upshift lamp bulb or failed indicatorLikely
- Damaged wiring or corroded connectors in the lamp control circuitCommon
- Short or open in the lamp driver circuitCommon
- Failed control module driving the lamp (PCM/TCM)Less often
How to diagnose & fix
Work through it in order
- Confirm whether the lamp itself works; replace the bulb or indicator if it has failed.
- Read freeze-frame data and inspect the lamp wiring and connectors for damage, shorts, or corrosion.
- Test the lamp control circuit for continuity and correct voltage from the module.
- Repair any wiring fault; suspect the controlling module only after the bulb and wiring check out.
FAQ
Quick answers
Is it safe to drive with P0804?+
Yes. This is an indicator-lamp circuit fault only — the engine and transmission are unaffected, though the light stays on.
Can I just clear P0804?+
You can, but if the bulb or lamp wiring is faulty the code will return; fix the circuit to clear it for good.
Related codes
Often seen with P0804
Read & clear P0804 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