Faulty upshift/skip shift solenoid (internal open circuit or short); Damaged, chafed or corroded wiring between the solenoid and control unit; Poor connection or water ingress at the solenoid or control unit connector; Blown fuse or fault in the solenoid power supply or earth; Mechanical fault in the skip shift mechanism or gear linkage affecting the solenoid; Fault inside the engine or transmission control unit driver circuit.

P0803

Upshift/Skip Shift Solenoid Control Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
03: FaultThe specific fault in that area

What it means

P0803 is the generic code for a fault in the upshift/skip shift solenoid control circuit. This solenoid is used on some manual gearbox applications to force a skip shift from first to fourth gear at light throttle to improve economy. The control unit sets the code when the voltage or current it sees on the solenoid circuit does not match what it commanded, for example an open circuit, a short or a failed solenoid.

Symptoms

Malfunction indicator lamp on
Gear shift indicator or skip shift behaviour not working as normal
Car forced into or blocked from second and third gear when pulling away gently
Difficulty selecting second or third gear at light throttle
Slightly worse fuel economy

Possible causes

Faulty upshift/skip shift solenoid (internal open circuit or short)likely
Damaged, chafed or corroded wiring between the solenoid and control unitlikely
Poor connection or water ingress at the solenoid or control unit connectorlikely
Blown fuse or fault in the solenoid power supply or earthpossible
Mechanical fault in the skip shift mechanism or gear linkage affecting the solenoidpossible
Fault inside the engine or transmission control unit driver circuitrare

How to diagnose

Read all stored codes and freeze frame data, noting when the fault set and whether other codes are present
Check for relevant technical service bulletins or software updates for the specific model, as the layout and operation vary by make and engine
Visually inspect the solenoid, its harness and connectors for damage, corrosion, moisture or chafing
Check the relevant fuse and the power supply and earth to the solenoid using the wiring diagram for that vehicle
Measure the solenoid coil resistance and compare it with the manufacturer specification
Test the control circuit wiring for continuity, short to earth and short to voltage, with the connectors disconnected
Command the solenoid with a suitable diagnostic tool, if supported, and check it clicks and the circuit responds
Clear the code and road test to confirm it does not return

How to fix

Replace the upshift/skip shift solenoid if its resistance or operation is out of specification
Repair or replace damaged wiring and terminals in the solenoid circuit
Clean, dry and secure connectors, replacing any that are corroded or damaged
Replace the blown fuse after finding and fixing the cause of the overload
Repair or adjust the skip shift mechanism or linkage as the manufacturer procedure directs
Only after all else is ruled out, repair or replace the control unit, or update its software if a known fault is documented

Can I keep driving?

Low severity

The car can normally be driven, as the fault mainly affects economy and the feel of the gear change. Book it in soon, particularly if you struggle to select gears or the lamp is flashing.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.