99' 4.3L S-10 PCM P0300 and P0442

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matt2tattoo
Posts: 10
Joined: Fri Apr 07, 2017 11:21 am
Vehicle: 99 S-10 4.3L

99' 4.3L S-10 PCM P0300 and P0442

Postby matt2tattoo » Mon Apr 17, 2017 9:40 am

I know I kinda left with an attitude on my recent topic, and for that all I can say is over-aggravated, I'm only human. That being said....I cleared my codes for MAP & MAF, ran fine for about a week, then SE Light came back on. Plugged in the OBD scanner and got the P0102. Cleared it again. Then...or now I get P0300 and P0442 codes when plugged back in and light is back on. My question is this.....is my PCM just junk and acting stupid?


kev2
Posts: 6573
Joined: Sat Aug 29, 2009 4:24 pm

Re: 99' 4.3L S-10 PCM

Postby kev2 » Mon Apr 17, 2017 10:11 am

vehicles, and computers aggravation is guaranteed. All you can do is one issue at a time- maybe grouping the priorities in correct order.

I will say PCM do go bad - I do not like to condemn them till all testing is done.. And helping on the net is working blind and deaf.

The p0300 a common misfire code - a misfire is 1)ignition,2) fuel, 3) mechanical.
It is the 1-2-3 testing needed no magic dart to pinpoint it.

P0442 is a EVAP leak small - called the gas cap leaks as that is a place to start.
Ideally a 'smoke' test is used to locate the leak.

A thought - Might want to check purge valve, leaking (vacuum when closed) would cause other issues... MAF and maybe a lean misfire...

matt2tattoo
Posts: 10
Joined: Fri Apr 07, 2017 11:21 am
Vehicle: 99 S-10 4.3L

Re: 99' 4.3L S-10 PCM P0300 and P0442

Postby matt2tattoo » Tue Apr 18, 2017 8:34 am

The one reason I suspect PCM is , back with the fuel pump a Mechanic that helped me did wire it wrong ( I came to find out) he wired the Blk/Wht stripe wire to the Blk and vise-versa, causing an electrical mayhem throughout my lights (break,tail,turn). Once I discovered it, I wired it correctly, but only after I drove it a few miles (10) and figured out my lights were off. Could something like this affect the PCM? Because ever since then, I've had this electrical issue in the truck. Again, I will point out to you that I do know what each and every code IS. It's the WHY that I'm looking for. Why is it that codes keep changing on me? It's another reason that I think the PCM is throwing false codes. I'm gonna mess around with the EGR valve today and clean it up to see if it makes a difference

kev2
Posts: 6573
Joined: Sat Aug 29, 2009 4:24 pm

Re: 99' 4.3L S-10 PCM P0300 and P0442

Postby kev2 » Tue Apr 18, 2017 12:20 pm

I will try to help if only a sounding board, and tech support - diagrams - troubletrees etc.

Why are you looking at EGR? Is there more codes?
REreading your post - the pump wiring shorted BLK to BLK/WHT - your fuel gauge OK?

What is status of p0300 and p0442? Any new codes?
- So far as condemning PCM I can not see a reason, I only see the few posts.
Can you see live data - that would really help with the big picture.


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