When you get a CEL light is it locked in until it is reset with a code reader?

Do certain codes cause the CEL to be locked in (hard code alarm) and others cause a CEL but once cleared (soft code alarm) on their own allow the CEL to clear on a engine restart for example?


For example, A couple of days I had the CEL light come on. When I checked the codes using TP, I had 2 codes showing in the registry. A P0170 Powertrain cel Trim (Bank 1) , which has come up a few times before. And a new one P04DB Powertrain, which to my understanding is a (Crank Case Over Pressure).

While moving my truck around in the drive a couple of times the CEL light was ON. Last night when I went out to move the truck again the CEL light was OFF. I haven't ran a code check on it yet to see if the two codes are still showing in the bank list or not.

Thats why I wondering if/when you get a code and a CEL light locks on (hard lock) or when condition clears CEL light off (Soft) alarm.

I have an appointment for in to go in under warranty on Monday but I know from the last time it went in that if it doesn't through the codes again after they reset them the dealer really won't do anything.

 

Some CEL's can be cleared by the ECM/PCM when you have the correct drive cycle sequences and the problem does not reappear.

 

BK...

My P0170 Code "fuel trim bank..." came on about every 1,000 miles, and light would turn itself off in about 8 key recycles. It remained stored in memory for a while. Came on at engine startup on each occasion.

Search P0170 on this forum.

Lots of pin tests- unsuccessful- nothing found. I did replace both air filters (not dirty), but no help. Then a bad injector found, but still that code and light every 1,000 miles. This went on for 8k miles. Finally dealer said Ford knows of code problem; no solution, just drive and reset (first verify code, then reset with my TorquePro). Got Re-flash months later. This was before the dual-bank Re flash came out. No codes since then. (10k miles).


I know nothing about your other code.

 

Thanks for the info.

JohnD333, I have another thread running about the the P0170 code on FTE. It pops every now then. I'm thinking the prom is the computer needs a set condition with a timer attached to it. More then likely it just has to short of a duration. We see this all the time in control logics with process.