PO453 and PO442 codes on 98 Chevy s10

Hi guys, so recently I purchased a 98 Chevy s10 with the check engine light on. Seemed like a good deal. Has a battery warning light constantly on and I have to turn and reset the ignition a few times each morning to get the engine to start but it ran relatively smoothly. I waited a day, then tried to reset the light by disconnecting the battery and cycling it. The light never cleared. Once my scanner came in the mail I ran it and came back with a PO453 (High pressure in EVAP) code.
Looked it up, could be a variety of causes, and as I don’t really have a place to tinker with it too much I started with the easy stuff. Checked gas cap, seems a bit weartherized and probably needs to be replaced. Got under the vehicle and had barely enough clearance to disconnect what I believe to be the FTP sensor .

Started the vehicle, stopped, then ran the code again, only this time it came up as a PO452 (EVAP pressure low). Reconnected the sensor, erased the codes and again the check engine light stayed on. Went to work today, code on. Got off and the check engine light was gone! Excitedly I ran the codes again when I parked at home and it still came up with PO452, but the Check Engine light is still off.

Kinda confused as I’ve never heard of that happening before. Hoping you guys had some thoughts on it.


The very first thing you to do is figure out this battery light

Test the battery. If it’s older than 5 years, replace it now. Its best days are behind it

Check the charging system after making sure the battery is charged and/or replaced

Should be around 14V at idle. By testing, I mean using a digital multimeter. Don’t place too much faith in the charging meter in the cluster. They’re not always 100% accurate

Make sure your belt and tensioner are good

You have side terminals. Make sure the bolts are tight and NOT stripped and/or corroded. Make sure the cables are also tight and not corroded

If in doubt, the battery bolts are available cheap at any auto parts store

Sorry if I’m not giving you the answer you want, but in my opinion, you have to make sure the truck starts reliably and is charging correctly, before worrying about an evap code

Good advice by dB4690 above, unless the electrical system is working properly w/the correct voltages, it is hard to say what other codes may or may not mean. Fixing that could involve replacing the battery, the alternator, maybe even the ECM, or – cross your fingers – just cleaning the battery posts from corrosion and tightening up some chassis grounds.

If you fix the electrical problem and the evap codes remains, this might be useful.


How could buying a vehicle with a CEL on be a good deal???

You could have taken it to any auto parts store on the test drive, to at least find out what codes were present and in history.
What if it came up with 15 codes stored…missfires, low oil pressure, 02 sensors, engine temp high, low coolant, etc., etc… That could let you know right away that this may be an engine on it’s way out that has experienced many overheating situations.
At the very least a poorly maintained engine.


On that note, why would you buy a vehicle with the red battery light on, at idle?

It’s obviously got a problem with the charging system

Why the heck would you try to sell a vehicle with the red battery light on at idle

That’s literally a red flag, and would turn away many potential buyers

Replacing the alternator on an S10 is cheap and easy. And then you wouldn’t have that glaring red flag staring you in the face every time you’re driving the truck

I think many mistakes were made here, both on the buyer’s and seller’s part


When the CEL goes out, that means the code condition has not been detected for a certain number of drive cycles (3-10) but the code is stored for a number of drives cycles after the CEL goes out, (10-30) If it is not detected after the specified number of drive cycles, then it is erased from memory.

It is possible that the codes you got were caused by the previous owner chronically overfilling the gas tank. If you stop adding gas after the handle first clicks off, you might never see these codes again. Usually this issue causes P0446 but it might cause the codes you had.

“How could buying a vehicle with a CEL on be a good deal?”

As illogical as it may seem, there are a whole lot of people out there who think that it is “normal” to have a CEL perpetually lit-up on their instrument panel. Yes, it is illogical, but it is also reality that this myth is in the normal scheme of things for many people. Obviously, this myth originated (and is perpetuated) with people who simply don’t maintain their cars properly, and who don’t do timely repairs, but that segment of the population is fairly sizeable.

If I can give you an analogy, when I was a school counselor, I heard quite a few parents tell me that “all teenagers have a police record”. The folks verbalizing this myth were those whose kids were jail birds, and they simply wanted to make themselves feel good about their errant, unsupervised kids. When I informed them that I enjoyed a very good relationship with the local PD, that the principal and I received arrest reports from the local PD, and that–in reality–less than 5% of our student body had ever been arrested, these parents couldn’t believe that it wasn’t “normal” for all kids to have arrest records.

The bottom line is that people create scenarios in their minds in order to make themselves feel better about their own shortcomings.

Aint that the truth. Our little baby wouldn’t do that.

Some of us brag, of how many miles we have on an engine from maintaining it well.

Others brag how long their engine has lasted with a CEL light on all the time.
It’s their badge of honor for them. “that’s been on for three years now and I haven’t had a problem…glance out your window and watch for traffic…I can’t see through the smoke”!!!


Of course in many (most?) states you won’t get through the next annual inspection.

It’s their badge of honor for them. “that’s been on for three years now and I haven’t had a problem”

This is from before your time in this forum, Yosemite, but the older veterans of the forum may recall a woman who told us that the CEL on her vehicle (either a Suzuki or its Chevy clone) had been “on” for the past 16 years, and she wanted us to tell her–from afar–what was wrong with her vehicle. She also asked some questions that could have easily been answered by simply opening her Owner’s Manual.

When we told her that she should actually read the manual, she responded with something along the lines of “only an engineer could understand it”, despite the reality that Owner’s Manuals are purposely written on an 8th grade reading level. We also suggested that she needed to have the stored trouble codes “read” at an auto parts store in light of the probability that after 16 years, there could be…many…stored trouble codes.

She did not react well to any of the suggestions, and was apparently of the opinion that if we couldn’t instantly diagnose her vehicle via cyberspace, we weren’t of much use to her.

I can’t substantiate any claims, but I’m sure there are a few techs out there that if a fifty dollar bill is taped over the access port for the scanner, the car passes.

I did hear of someone (a Tech) who ran the test on his own vehicle, but entered the ID info for another persons car. Not sure if that can be done either, and I really don’t want that answered here. We don’t need to give anyone any ideas.

Someone stole by yearly sticker off my plate and when I was pulled over, I was told it’s common for them to be stolen and put on a car that has no sticker. As long as you don’t break the law and get pulled over you’re safe. I just had to go get a replacement…no ticket because it’s so common he understood.


Actually Yosemite, due to inflation it’s a Benjamin now. I prefer to brag about my 96 four wheel drive Suburban with almost 350k on the clock, no check engine light on. And the bulb aint burned out. Razor blade keeps the thieves off your sticker. Simply stick it on the plate then slice it a few times. Thieves will see it’s too much work.

At the time mine was stolen, the stickers are made that if you try to peel them off they just tear’s it’s been that way for years in Wisconsin yet somehow they find a way. It took me less than a minute to think of how to beat it and your idea with the razor blade…simple too, but I won’t post it.


You put packaging tape over the sticker before peeling it off. Body shops and windshield repair guys know this trick because they often have to transfer stickers from an old windshield to the new one.

Exactly. Now all the thieves know @Keith.


Buying a vehicle with the CEL on or the Alternator light on might be something to consider – if the price was right. Especially if a person was DIY’er inclined, and looking to build some vehicle equity, not by paying for it in cash, but by crawling under it with a wrench. Most every vehicle has problems, even new ones. It’s all a compromise. Me, I’d want a pretty good-sized discount to buy a car with those lights on, but if the discount was big enough and I was in the market for a car, I’d definitely consider it.

Multimeter is on the way, ended up that I wasn’t pressing hard enough on the clutch, so the switch needs to be adjusted. Other than that it starts fine and the battery icon goes away upon ignition.

As to why I purchased a vehicle with the CEL on; I grew up in a family that could only afford used vehicles, and my father is a pretty decent backyard mechanic. Sometimes we’d pick up a vehicle if it was cheap enough and the repair work reasonable.

I’ll readily admit I’m way less knowledgeable and experienced than I should be given, my history, but I did some soft-checks before, during and after the test drive for the potential major issues I know about, the usual “dealbreakers” and was told that the likely repairs made it a good deal at a grand. Time will tell I guess. Replaced the sensor and cleared the codes, we’ll see if that was the issue.

Those are Evap codes and would have nothing to do with the clutch or how far you were depressing the pedal. This vintage of S10 would not cost much to fix an evap issue.

To me, evap codes would not be a deal breaker along with many other codes, but knowing what those codes are could give you a much better chance at a good discount.

Some codes…or groupings of codes would be a deal breaker, not all but some.
I’d sure want to know why the light is on, is all I’m saying.
Some combinations will point to poor maintenance all around and that could be a deal breaker.


OP writes …

battery icon goes away upon ignition

That’s how it is supposed to work when there is no alternator problem. The battery light is designed to come on with the key in “on” but the engine not started. Same as the check engine, oil, and and brake dash lights. That’s so you can verify the warning bulbs are working. If once the engine is started, the battery light goes out, that means the alternator and battery are working as expected.

Edit: Re: Clutch safety switch.

That part – on my Corolla at least – is to prevent the engine from cranking unless the clutch pedal is depressed first. It’s a safety feature in case little kids in the car try to turn the key to see what happens. That part failed on my Corolla, and needed replacement. No harm done to try to adjust it, but I expect you’ll end up having to replace it. On the Corolla it is located near the clutch pedal itself.