PSP Switch Input Malfunction
Your engine's power steering pressure switch isn't communicating properly with the computer, like a broken intercom between the steering system and the brain. The ECU can't tell if power steering pressure is normal or high, which affects engine idle and performance.
The ECU monitors the PSP (Power Steering Pressure) switch signal to adjust idle speed and fuel trim when steering load increases. The switch should toggle between high and low voltage states based on steering pressure demands. When the ECU detects an out-of-range or stuck signal, it flags a malfunction.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| PSP Switch Signal Voltage | 0.2V (inactive) to 4.8V (active) with clean transitions | Stuck at one voltage, erratic transitions, or no signal detected |
| Signal Response Time | Switch toggles within 200ms of steering input | No response or delayed response to steering pressure changes |
Code P1660 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, P1660 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.