P1725: Insufficient Engine Speed Increase During Self Test

P1725 is a manufacturer-specific powertrain code that sets during the PCM's Key On Engine Running (KOER) self-test. The PCM commands a brief, controlled throttle blip and measures the RPM response -- if the engine speed doesn't climb to the expected threshold, P1725 is logged. It's most common on Ford vehicles but appears across several makes that run KOER diagnostic routines.

The engine's failure to respond is rarely about raw power. More often it points to idle control problems: a gummed-up throttle body that won't open cleanly, a sticking or failed idle air control (IAC) valve, or a vacuum leak that's already pulling the idle down before the test even starts. A weak or erratic throttle position sensor signal can also cause the PCM to misread how far the throttle opened, triggering the fault even when the hardware is functioning.

Before replacing parts, check for vacuum leaks at the intake manifold gasket and any hoses connected near the throttle body -- these are the most common root cause on higher-mileage engines. A throttle body clean with an appropriate solvent is a low-cost first step. If the code returns after that, a live data scan comparing actual versus commanded RPM during the self-test will point you toward the IAC valve or TPS before you commit to a repair.