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.
Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.
Symptoms
- Check engine lamp after two trips
- 1-4 lockout no longer works (1-2 always possible)
- Otherwise no change in driving
Most likely causes
- Solenoid unplugged or replaced by a skip-shift eliminator with the wrong resistance
- Connector at the gearbox loose or corroded
- Solenoid coil open
- Harness damaged
- Engine module driver faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0803 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 8: Transmission
- 03: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0803?
Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.
What causes code P0803?
The most common causes are: solenoid unplugged or replaced by a skip-shift eliminator with the wrong resistance; connector at the gearbox loose or corroded; solenoid coil open.
Related codes
- P0804Upshift/Skip Shift Lamp Control Circuit
- P080BUpshift/Skip Shift Solenoid Control Circuit Range/Performance
- P080CUpshift/Skip Shift Solenoid Control Circuit Low
- P080DUpshift/Skip Shift Solenoid Control Circuit High
- P0801Reverse Inhibit Control Circuit/Open
Sources
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 19OBDG03A Diagnostics
- gsi.ext.gm.com: 2006file1
- en.wikipedia.org: Shift blocking
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.