Code 43, low voltage at the EST circuit. What conditions need to be met before this code is set by the ECM? I ran into it today when I was at WOT having a little highway fun. Car didn't seem to run worse, but it definitely seems to be sucking more gas. (Probably unlreated, I just installed a Holley StealthRam without an AFPR and I have Ford SVO 24# injectors rated at 38psi, new pressure is 43psi)

if you disconnect the lead to the knock sensor, with key on, you should read 4-6 volts. if no voltage, that is probably the culprit. if it's over 6V or less than 4V, probably shorted to ground or bad ecm.

if you have voltage, check the knock sensor by reading the resistance to ground. should be 3300-4500. if all that is good, then possibly the prom in the ecm.

also (and you may already know this) if you have to change the knock sensor, it is also the drain plug on that side, so you'll have coolant coming out at ya...

Yeah, I usually drain the block by removing the knock sensor.

Thanks, that'll be helpful tomorow when I try to trouble shoot it.

Since we are dealing with the knock sensor I'll ask it in this thread as it may be related.

Since the stealthram install I have been getting audible knock at part throttle just before upshifts. I don't hear it at full throttle but I'm sure its there. I don't have a scanner, nor a laptop and ALDL cable to read it.

Could knock cause this code to be set?

i would say that it would cause it to set, as that is its purpose, but it only takes like 1/2 second to set the code if your voltage is too high or too low on it. i would check your voltage first, and your resistance. if you do a search, there are some other things that affect a 43, i think, but basically, the book says to check your voltage, sensor, and ecm/mem-cal...