Multiple Codes

[53burb]

Everybody,
Thanks to truckdude239, my obd connecting port works now. So here are the codes that showed up:
171 - System too lean (twice - both banks)
174 - System too lean (twice - both banks)
131 - Circuit Low Voltage
137 - Circuit Low Voltage
151 - Circuit Low Voltage
157 - Circuit Low Voltage
101 - Mass or Volume Airflow circuit range/performance
442 - Evaporative emissions system leak

This is on a NBS '99 Silverado 4wd, 4.3v6, 5-sp manual & 120,000 miles.
The "check engine" light comes up intermittenly.
The engine runs fine EXCEPT when it is cold. It seams to run kinda lean for the first mile when it is cold.

Thanks for any help.
Chris

[truckdude239]

ummm, ummmmm and umm omg, never seen that many in one computer

[bighaas79]

Originally Posted by truckdude239

ummm, ummmmm and umm omg, never seen that many in one computer

I had an 04 kodiak in once that had I believe 15 codes in the pcm and 12 in the ebcm. Also had like a 93-94 buick with 22 codes in the pcm. Trick is to be able to figure out which ones are the cause codes and which ones are effect codes. That can significantly make life easier.

[truckdude239]

442 - Evaporative emissions system leak is normally a gas cap or there is a vent valve on top of thee tank that goes bad

[bighaas79]

I'd say the one you need to look at first is the p0101. Either your mass air flow is dirty causing false readings or just not working correctly, which when the pcm puts the readings from the O2 sensors and the maf sensor together they are not correlating. That would be my first thought without actually being able to look at the data stream first hand. Seeing the data stream makes a huge difference when diagnosing this stuff. If you can look at the data stream watch your maf grams/sec reading and crack the throttle and see if the number climbs up say like around 100 or so if not I'd say maf hot wire may be contaminated, or just not working.

[truckdude239]

po131 is o2 sensor low voltage bank 1 sensor 1
po137 is 02 heater malfunction bank 1 sensor 2
po151 bank 2 sensor 1 o2 sensor cirit malfunction
po157 O2 cirict low voltage bank 2 sensor 2
po101 is normally a bad mass flow sensor

[truckdude239]

i'd look at new mass flow and new o2 sensors or a bad ecm

[truckdude239]

according to shop key the po442 code is not suppose to set if po131 and po133 are set which confuses me

[bwood]

I have seen MAF problems with aftermarket washable/oiled air filters (K&Ns on a 99 S10 Blazer w/4.3l and 01 S10 w/4.3l). It usually occurs after the filter has been washed a few times. The freshly oiled filter needs to sit in the open air to let the solvents evaporate before installing. What happens is the filter is installed prematurly and still thin oil is pulled from the filter and sticks to the first obstruction-MAF screen. On the Blazer, it had so much oil on it that the little air foils in front of the sensor wires were caked and had wrapped around on to the wires and you could barely see through the screen. On the S10 the screen was stopped up on one side. On the Blazer, the MAF code showed up and also a lean code (don't remember numbers, it was a while back). I was able to clean the S10's sensor with CRC MAF cleaner but the Blazer had to be replaced. Bought a new unit from NAPA and cleared the codes, all good since then.

[53burb]

Tanks everybody, i will spray some "mass air flow" cleaner in the maf tomorrow & start from there. Should I also disconnect the battery for 10 minutes to reset this code after I do this?

[truckdude239]

it should i would still find that vacuum leak thats the problem of your hard starting

[53burb]

Everybody, I disconnected the battery & cleaned the MAF & throttle body real good with a MAF cleaner. The battery was disconnected for about 20-30 minutes. The acceleration seemed alot better & it didn't have the same symptoms as before when cold, but it ran for a few minutes before I drove it. I then ran it to Checker's to have the codes read again. This time only 2 codes were shown for an O2 sensor. Nothing else. I mentioned that I disconnected the battery, but he said that would not erase them. It seemed to do it for me. I'll run it again tomorrow & we'll see.

[truckdude239]

well normal change interval is 100k on o2 sensors

[53burb]

I have ran the engine multiple times cold & disconnected the battery for 10+ minutes a couple of times & had the codes checked. The only code that shows now is 174 - system too lean. I'm not concerned about this right now. I believe the 442 code - gas tank leak, I believe was caused by the fuel pump NOT being installed correctly (NOT by me). I removed the bed & corrected this last week. All is well now. THANKS everybody for your help!!

[truckdude239]

if you fixed the vacuum leak i'd take it and clear that 174 code a leak will cause the 174 code

[53burb]

Ok, i guess i will spray some starting fluid around the intake then. Any other ideas of where to start from?? You mentioned earlier about the truck being hard to start & that it was possible vacuum leak, I thought you had gotten the posts mixed up, but the truck has never had that problem.

truckdude239 Re: Multiple Codes

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it should i would still find that vacuum leak thats the problem of your hard starting

[truckdude239]

if you fixed the gas tank where the pump was installed wrong i'd just clear any codes left in the computer.the po442 code is normally a gas tank leak/ bad gas cap which can lead to the po174 system to lean code

[53burb]

I've reset the computer by disconnecting the battery for over 10 minutes then had it checked at Checker's. The only code that shows now is the 174 code. IIRC, the 174 code has been there for a couple of years. I remember I ran it thru emissions over a year ago & this code showed up.

[truckdude239]

oh got ya then its an o2 sensor gone bad

[53burb]

That's what I figure...Thanks again for all the help!!

[MylilBowTie]

Ive heard if the upper intake manifold bolt are to tight it will create a vacuum leak.

[53burb]

Interesting, I guess the intake gasket could be smashed. I do remember that the intake gaskets were replaced by a shop that the PO took it to. I'll spray around the base of the intake the next time I change the oil, give a tuneup, etc....