Transmission Transfer Case Clockwise Shift Relay Coil Short Circuit To Ground
The transmission's clockwise shift relay coil has an electrical short to ground, like a wire touching the car's metal frame. This prevents the relay from properly controlling the transfer case shifting mechanism.
The ECU monitors the coil resistance of the clockwise shift relay by applying voltage and measuring the return current. It expects a specific resistance range; a short to ground drastically reduces resistance. When detected, the ECU logs the fault and disables the relay circuit to prevent damage.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay Coil Resistance | 70-90 ohms | Below 10 ohms or continuity to ground |
| Coil Voltage Drop | 11-13V under load | Below 2V or 0V (short condition) |
Code P1828 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, P1828 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.