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Recurring PO102 and PO443 in a '99 GP GT, 3800 series II, non supercharged

E

EricR

New member
Greetings.

My wife's beloved still shiny '99 GT keeps popping up a recurrent pair of codes. The first time, it was just the PO102, MAF sensor low output. I replaced the sensor, cleared the code. But when I re started the car, it popped right back up.

The car has the symptoms of a bad MAF, unstable idle, hesitation off idle on acceleration, and some times (never happens to me but happens to her) it does not want to re start hot. Used to do 300 miles to a tank in the city and is now down to about 260.

I exchanged the sensor today as it was under warranty. Again, change sensor, clear code, start car, BAM! 15 seconds after you start it, the MIL comes back on.

I finally bought a scanner, an Actron CP9580, rather than the code reader I had. So I can get real time data. I have not had much time to work with it yet but it will record, freeze frame and graph if needed. However, I did use the CODE CONNNECT feature which leads to common repairs for this code, and beyond replacing the sensor there is repair sensor wiring harness and repair sensor ground, replace ignition switch (don't know how that would relate) and replace PCM.

Anyway, back to the problems- you can clear the codes with the engine running, drive all over with no appearant issues, but when you shut the car off and re start, these two come right back up.

Now, I don't have a factory manual with a nice engine harness diagram but in my experience with electronic engine controls (diesels) a lot of things can be traced back to a bad common ground in a harness plug or an abraded/corroded connection.

Also, I have a coolant level switch I gave up and disconnected due to erroneous readings, and the exterior temp reads low by 15* and it all used to work fine.

The car has 210,000 on it, I repaced the original MAF at about 160,000, had NO trouble until last month at 108,000, then today as mentioned in the first paragraph I exchanged it to no avail.

Does anyone have any thoughts on this or have access to a wiring diagram for the engine? This whole thing seems to me to be a harness or connection problem. Want to get my poncho back to normal!
 


po443 is a evap code, the maf, have you checked the wires to the maf plug, if they are cracked or missing insulation the wires get whats knows as dry wire, and can throw the same code as a bad maf. new pig tails are about 10 bucks new.
 
I would like to share a scenario that turned out to be a good reminder/lesson of checking the simple stuff first when troubleshooting an issue with your car.

Along with the Jeep Liberty that my wife drives. My DD is a 2004 Pontiac Grand Prix 3.8L Non-SC with 168,000 miles on it. About 4 weeks ago, the Grand Prix came up with a CEL light. This was at the same time I was also dealing with the "Jeep Liberty - No Crank" condition. I was pre-occupied with getting the Jeep up and running. I ignored the CEL on my Pontiac.

The symptoms of the Pontiac were hesitation, pinging/detonation, hard time starting and occasionally stalling. I get the car scanned and the stored codes are P0102 and P0443. Which points back to a failed MAF sensor and a leaky EVAP component.

Figuring I had a bad gas cap. It's replaced with an aftermarket cap. I also pull of the MAF and clean it with some MAF cleaner. Theres no change. Codes are still persistent and still runs like crap.

Assuming the MAF is bad. I go ahead and replace it and I also remove the throttle body and clean all of the carbon buildup from it. Although the throttle response is better. The root issue is still there.

So now I'm kinda at a loss of what it could be, Figuring I have a rogue vacuum leak somewhere and the car is sucking air . I spray carb cleaner trying to find the leak. No leak can be found.

Now I'm completely discouraged not knowing where to look next. So I go to Google and do a search on the 2 codes and some of the results lead me to a Grand Prix forum where I discover that these 2 components are on the same electrical circuit and if the fuse is blown it will generate the resulting codes.

I go out once to the car and open up the panel and what do I find?

The 10 AMP fuse is inserted halfway into the slot and it just barely in there. I began to laugh when I realized what had happened.

When I was beginning the trouble shooting process of my wife's Jeep. One of the first thing's I did was to swap battery's. The battery for the Grand Prix is located behind the passenger headlight and in front of the fuse panel.

The battery is a tight fit, so much that when your installing it, You need to have the fuse panel open and bring the battery in at a 60* angle to get it in. Even with all of that, it's still a tight fit.

So what happened was when I was swapping battery's, The corner of the battery must have caught the fuse and knocked it out of place.

While I was still in flashback mode upon seeing the fuse., I remembered when I tested my wife's battery in my car, That my car was hard to start and immediately registered the CEL. It never dawned on me to check the fuse, since I was so consumed on what was wrong with my wifes Jeep.

So long story short, I reinserted the fuse and cleared the CEL and the car is now running absolutely awesome with the new MAF and clean throttle body.

Hope this helps everyone, that when your troubleshooting a problem. Don't forget to start with the small first.
 
After some research last night, 'twas indeed the fuse! Car running is running great, MAF is giving me actual readings in the data mode. Now I have a new gizmo to play with! Realtime data, % of relative load etc right on my screen!

Thanks for the responses guys. My fuse was blown. Going to hope it doesn't happen again.
 
BillBoost37 said:
Which fuse.. ya know so future folks can find it quicker.
Click to expand...

#21 in the underhood box behind the battery, VERY hard to get the cover off with the battery in place! But it's a 15amp mini fuse, I need to buy a factory service manual as the Chilton stuff is not very good on schematics.
 


Loosen your battery and push it toward the radiator then retighten it. Unless it's the big mamou it shouldn't be a stretch to get that cover off.

Thanks on the info.
 
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