Not totally true for LH 2.4/EZK about a code always being set for a missing rpm signal (as seen through the CPS). You can easily have a nostart from a bad CPS without a code, hence why we have so much trouble figuring it out some days. The control units basically don't know the engine is turning over without the signal so have no reason to set a code if the CPS has outright failed. Once the engine is running, it's a different story for a failing CPS. EZK ICU will set a 2-1-4 code on port 6 for an intermittent rpm signal, but only after the engine has been seen turning over. The ECU will set a 1-3-1 code on port 2 if it's not seeing any kind of reliable rpm signal (either a pulsed or stationary ground) being passed to it by the ICU, basically a wiring issue or a very flaky pulse. Only if you're lucky and the CPS doesn't outright fail, but is providing a weak or intermittent signal will you tend to get a code, most often the 1-3-1 code in my experience. Leastwise that's how I understand it.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now