P0803 Code: 1-4 Upshift (Skip Shift) Solenoid Control Circuit

What the P0803 code means

On some six-speed manual transmissions (for example in the Corvette and Camaro), a solenoid forces a shift from 1st to 4th when you accelerate gently at low speed, to reduce fuel use.

The computer watches the control circuit from its own driver transistor. The P0803 code points to an electrical fault in that control circuit. Before you replace the component, check the fuse, relay, connector and wiring, because they are the most common cause.

If the solenoid fails, the skip shift may not work or, the other way around, may be active all the time. It does not affect safety, but it does affect comfort.

Always start with the simplest items: fuse, relay and connector. Then check power, ground and signal with the component connected (using back-probes), and finally the continuity of each wire up to the computer. Only if all of that is good should you replace the component.

P0803 code symptoms

• Check engine light or another warning light on.
• The shifter forces a shift from 1st to 4th.

Likely causes of the P0803 code

1. Damaged connector, loose, broken or corroded.
2. Blown or faulty fuse or relay.
3. Wiring cut or shorted between the component and the computer.
4. Failed component: the coil, the motor or its internal electronics.

How to diagnose the P0803 code step by step

1. Command the component with the scan tool and see whether it responds.
2. Check the fuse and relay. Measure voltage on both sides of the fuse, and swap the relay with an identical one.
3. Measure the supply at the connector. Battery voltage with the key on or when it is commanded.
4. Measure the component resistance and compare it with the manual, and check the insulation to ground too.
5. Check the control wire for continuity up to the computer and for shorts.

How to fix the P0803 code

• Repair the connector, the wiring or the power supply.
• Replace the 1-4 skip shift solenoid if it does not respond with correct power and command.
• Clear the codes and verify the repair.

Technical reference data

• 12 V solenoid.
• These are approximate values: check the manufacturer data for your vehicle.

Brand-specific notes

This code is typical of GM vehicles with the Tremec T56 and TR6060 manual transmissions, which are the units the source names.

P0803 on GM

Typical on GM vehicles with the Tremec T56 and TR6060 six-speed manual transmissions.

Frequently asked questions about P0803