P0803Upshift/Skip Shift Solenoid Control Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- GM's skip-shift (CAGS) on manual gearboxes such as the T56 and TR6060 uses an engine-module solenoid in the shifter housing that, at light load and low speed blocks the way from 1st into 2nd and 3rd so the driver shifts 1 to 4 – a measure for fuel economy ratings; the 1-4 lamp (P0804) shows it. P0803 means the solenoid control circuit is open. GM's tables check the low-side driver while it is off: too low a voltage or over 200 kΩ to ground, with at least 9 V and over 250 rpm, 5 of 6 samples of 250 ms (2019 LT5: 20 of 25), type B with the MIL after two trips; shorts are P080C and P080D. An open circuit leaves the solenoid unpowered, so 1 to 2 always works. 'Skip-shift eliminators' with the wrong resistance are a frequent cause.
- What you may notice
- Check engine lamp after two trips
- 1-4 lockout no longer works (1-2 always possible)
- Otherwise no change in driving
- Likely causes
- LikelySolenoid unplugged or replaced by a skip-shift eliminator with the wrong resistance
- LikelyConnector at the gearbox loose or corroded
- PossibleSolenoid coil open
- PossibleHarness damaged
- RareEngine module driver faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.