1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction
The transmission's skip-shift solenoid (which forces you to shift from 1st directly to 4th under light acceleration) isn't responding properly to the ECU's commands. It's like a remote control that won't talk to the TV—the signal is being sent, but nothing happens on the receiver end.
The ECU sends a voltage signal (typically 12V PWM) to energize the skip-shift solenoid during light-load conditions. It monitors the solenoid's current draw and response time to confirm the coil is operating and the valve is actuating. If current is absent, too high, or the solenoid doesn't respond within expected timing, a fault is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Solenoid Current Draw | 0.5–2.5 amps when energized | No current or >3 amps (short circuit) |
| Command Response Time | <200 milliseconds | >500 milliseconds or no response |
Code P1102 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, P1102 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.