Check engine went out and staid out

[Black GT]

My 2001 GT used to throw code p0174 on a weekly basis. One day over a month ago the CEL light was lit and I drove threw about a foot of water and the light went off and has stayed off. I am not sure if this is good or bad, could I have possibly shorted the circuit that was causing the light to come on? How could I test for this?

 

[wmburns]

Is your question about the check engine light itself? Turn the key on but do not crank. Does it come on during the initial key on "lamp test". If so, then the check engine light is good.

Now crank the motor. Does the check engine light go out during cranking? If so, that means the PCM is getting a good CKP signal.

Turn the ignition switch off and back on. Does the check engine light come back on?

Another option is to scan the PCM with an ODB2 scanner. Does the ODB2 scanner say that the MIL is on?

Perhaps an even better option is to use a ODB2 scanner with two way activation. Use the ODB2 scanner to command the MIL to turn on. Does the check engine light come on?

Here's some information on an affordable Windows based ODB2 scanner unit.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

 

[Black GT]

The CEL comes on with the key on engine off. The light goes out while cranking the engine. The CEL does not come back on after turning the engine off. However I plugged in the OBD2 scanner and it had a p0153 code. I erased the code but find it strange the code did not illuminate the CEL. I have a inova model 31703 OBD2 scanner. I think its a pretty informative scanner if I can figure out how to use it. About all I know how to do is read and erase codes and pull up freeze frame data. I have no idea what the data means though. By the way,Thank you for your help.

 

[wmburns]

However I plugged in the OBD2 scanner and it had a p0153 code.

I think the key is understanding the difference between a "pending" DTC code and a "hard" DTC.

If there's a DTC code and the MIL is not on, then the code is a pending code. A pending DTC usually are pending while waiting for multiple drive cycles to pass with the DTC still occurring.

OBTW, any ODB2 scanner will tell you IF the MIL is to be on or not.

>>From Ford manual
P0153 - HO2S Sensor Circuit Slow Response (HO2S-21)
See DTC P0133

P0133 - HO2S Sensor Circuit Slow Response (HO2S-11

• Contaminated HO2S sensor.
• Exhaust leaks.
• Shorted /open wiring.
• Improper fueling.
• MAF sensor.
• Deteriorating HO2S sensor.
• Inlet air leaks.