* OBDI Systems and Intermittency: OBD I systems (like in your 1992 Dakota) are less sophisticated than later OBD II systems. They often only illuminate the CEL when a problem is *currently* detected. If the issue is intermittent (like a bad connection that's sometimes loose), the light will flash or go off when the condition isn't present. The code 27 might only appear when the engine is starting, and disappear once the engine is running.
* Self-Diagnostics: The system runs a self-test, and if the problem isn't continuously detected, the light may turn off.
* Thresholds: The system might have specific thresholds. The malfunction might be minor enough not to trigger the continuous illumination of the CEL.
* Sensor Problems: A crankshaft position sensor can fail intermittently due to wear, loose connections, or even a failing sensor itself. It could work perfectly at times and then malfunction other times.
In short: A flashing or intermittently illuminated CEL with code 27 on a 1992 Dodge Dakota strongly suggests a problem with the crankshaft position sensor circuit, even if the light isn't constantly on. Ignoring it is risky, as a failing crankshaft position sensor can lead to a no-start condition or rough running. You should still investigate the problem thoroughly, even if the light isn't always on. This usually involves checking the sensor's wiring, connections, and the sensor itself for proper operation.
