P0804Upshift/Skip Shift Lamp Control Circuit
- Generic OBD-II code · Powertrain
- How the car detects it
- With GM's skip-shift (CAGS) on manual gearboxes, a '1-4' lamp in the cluster tells the driver that the lockout is active and to shift from 1st directly into 4th. P0804 means the control circuit of this lamp is faulty – open, shorted, or the lamp does not follow its command. No GM table from 2004 to 2025 available to us contains it, because newer cars switch the indicator by a CAN message from the instrument cluster without a separate engine-module line check; the code therefore mainly concerns older vehicles with a lamp driven directly by the engine module. The lockout itself (P0803) keeps working, only the hint is missing; there is no limp mode, and the MIL behavior is not documented.
- What you may notice
- 1-4 lamp never lights or stays on
- Possibly check engine lamp
- Lockout works without the hint
- Likely causes
- LikelyBulb or LED in the cluster faulty
- PossibleWire or connector between engine module and cluster open or shorted
- PossibleInstrument cluster board faulty
- RareEngine module output faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €10 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.