1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction
Your transmission's skip-shift lamp circuit isn't communicating properly with the engine computer. Think of it like a traffic light that won't turn on—the signal is there, but the light itself has a broken connection.
The ECM monitors the skip-shift lamp circuit voltage and resistance to ensure proper control signal delivery during low-load upshifts. When throttle position and engine load are minimal, the ECM commands the lamp circuit to guide drivers to shift from 1st directly to 4th gear. A fault occurs when circuit resistance, voltage, or continuity falls outside expected parameters.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Lamp circuit voltage | 12V when active, 0V when inactive | Voltage stuck high/low or no response to ECM command |
| Circuit resistance | Less than 5 ohms when energized | Greater than 10 ohms or open circuit condition |
Code P1103 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1103 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.