The pesky CEL is back. Has anyone had a similar situation?

[Josh B]

I had a 87 that didn't pass and at the test they wanted $250.00. It only had 5 emissions components, each one costing appx $50.00, so I studied up on them and picked one and replaced it.
The next day it passed emissions.
If that doesn't help I'll loan you my CEL, I can guarantee it won't come on

 

[Sdude2008]

the output of the flex sensor/replicator is a digital signal that changes frequency to indicate the alcohol content.
"good" code readers can display that output, as a percentage or out of range.

I would try to get an accurate reading on that wire before swapping the PCM

Thank you.

Looks like the expected frequency is 40 Hz - 160 Hz. Thanks

 

[Sdude2008]

I had a 87 that didn't pass and at the test they wanted $250.00. It only had 5 emissions components, each one costing appx $50.00, so I studied up on them and picked one and replaced it.
The next day it passed emissions.
If that doesn't help I'll loan you my CEL, I can guarantee it won't come on

I had a 1990 Mercedes with no obdii port. I swapped the seat belt light with the cel and passed.

Next year my 99 is exempt ugh.

Thanks

 

[James Morse]

As to the keys (PATS), when I got the '99 it had only one key so I had 2 more made and they did it right at the locksmith no problem. I think that's one of the earliest PATS systems so it could be a little "balky" meaning in the marrying of the key you can't rush the process but it does work just fine.

Now if you get a new computer and have no keys it might be more involved because I think you have to have one "original" key but others will know... if you end up there.

 

[Sdude2008]

As to the keys (PATS), when I got the '99 it had only one key so I had 2 more made and they did it right at the locksmith no problem. I think that's one of the earliest PATS systems so it could be a little "balky" meaning in the marrying of the key you can't rush the process but it does work just fine.

Now if you get a new computer and have no keys it might be more involved because I think you have to have one "original" key but others will know... if you end up there.

Since my 99 will be smog exempt next year I decided to just fail this year and pay my reg. BUT the cel really does bother me and from everything I've checked it does seem like the pcm is at fault. I have two keys now. If/when I change the pcm do the keys need to be programmed to it before I put it in the truck? I've also seen ads for 'plug n play' pcms where they use my vin somehow. Sorry if my questions are uninformed but thank you for the input.

 

[James Morse]

It's a really good question, and I have no idea, but I'm sure someone on here does know.