I just picked up my 97 F150 after having the head and lower intake gaskets replaced. Sounds pretty good and seems to run o.k., but now the check engine light is back on. Does the computer retain codes that were previously detected? Is this typical at all after this type of work, or could it be an artifact from the problem before, which was a coolant leak in the lower intake?

Ford150td

 

I think it will hold them for something like 60 starts. I bet there is a vacuum line or electrical line off. Get the code(s) read.

 

With a code reader you can clear any old codes.

 

It is probably a new condition.

The mechanic SHOULD have disconnected the battery while working on the gaskets for his own safety.

Further, it it was an "old" code that forced a CEL, the CEL would have been on when the truck was picked up.

The PCM will retain stored codes for either 40 or 80 drive cycles, depending on the revision of firmware, for conditions that no longer are present.

For the 97, you can reset the computer by removing a single fuse. It's a 5A fuse located in that small, 5-position box mounted to the inside of the fenderwell, tucked back into the corner near the firewall.

Of course, if you reset the computer, you won't know WHY the CEL is currently on. Therefore, get it scanned first.

Steve

 

I pulled the codes and it was identical to what I had seen before, which was a bad O2 sensor, bank 2, sensor 1. Before I had the gaskets changed I changed both sensors on the driver's side. This did not fix the problem and before diagnosing the lower intake manifold leak, I then replaced the sensor on the driver's side manifold, thinking that perhaps it got coolant in it or was defective. So I replaced a 2-week old O2 sensor with a brand new one, and the code came back. The same code, O2 sensor, bank 2, sensor 1. Can anyone confirm that I changed the correct sensor, the one on the driver's side on the manifold (I had also changed the one downstream on the driver's side as well)? Could the sensor that is causing the code be on the passenger's side for some reason? I assumed bank 2 was plugs 4,5,6 not 1,2,3 for this truck.

 

Bank 2, sensor 1 is the front one on the driver's side.
Do you know the actual code that was received and not just the description?