1996 Sierra can’t get rid of MAF code

[zakkb787]

Shot in the dark here but maybe someone knows. Picked up a 96 Sierra with the 5.7 Vortec. I can’t get rid of a p0102. Comes up as MAF circuit low. Tried two different sensors. One being new. The old sensor the truck runs rough when plugged in. Unplug it it runs fine. Truck runs great with the new sensor. No stumbling no rough idle or anything. 3 wire pigtail has 12v to ground for power and 5v to ground signal. But the code will not go away. Left negative cable undone all night twice and still on. Tried to clear multiple times with a scanner. The light turns off and immediately back on. And when it blinks the truck stumbles. No Intake leaks that I can see or vacuum via some brake cleaner sprayed everywhere. I’m at my whits end here.

 

[2004LB7]

I would check continuity of the wires back to the ECM. Make sure you have no breaks or bad connections especially on the signal wire.

 

[NC-smokinlmm]

Clear it with a tech 2 or solas scanner first, stored codes can't all be cleared with cheap scanners...

 

[zakkb787]

Clear it with a tech 2 or solas scanner first, stored codes can't all be cleared with cheap scanners...

I thought about that. Will give that a try. Thanks man

 

[DAVe3283]

If removing the battery cables overnight doesn't clear it, the code is getting set again. Those old ECUs (and even new ECUs AFAIK) don't have a way to retain error codes in memory once the battery is disconnected for more than a minute or two.

I would do what 2004LB7 suggested and trace all the wires for the MAF back to the ECU, looking for damage, corrosion, loose connections, etc. I think you still have a physical problem.

 

[zakkb787]

Could there still be a problem even if the wires test good? What I’m not understanding is I have the correct voltages

 

[Chevy1925]

Could there still be a problem even if the wires test good? What I’m not understanding is I have the correct voltages

yup, it would mean its a ECM issue. make sure the wires back to it and coming out of it all have good connection and are not being pushed out as you plug the harness in. otherwise it may be the ECM having internal issues.

 

[2004LB7]

When you measure the voltage coming out of the sensor whare are you taking the measurements? If it is right at the sensor then a bad wire, connection or otherwise can prevent the signal getting back to the ECM. This is why you need to check the wires all the way back.

The fact that you have good voltage to the sensor should rule out that wire.ake sure you have a good ground and that the sensor signal wire doesn't have more then an ohm or so back to the ECM. Ideally zero ohms on all wires

 

[zakkb787]

Measured the voltage at the plug for the MAF. I’ll check out the wires. I’m tired of working on stuff

 

[NC-smokinlmm]

Get a test probe and test ground the maf and see if the code clears.

 

[minerigger]

Had that on my work truck recently...turned out to be a NoX sensor issue along with the maf

Sent from my SM-G930V using Tapatalk

 

[zakkb787]

That’s what I’m beginning to be afraid of. Chasing down problems that I don’t know where to start. If the wires check good it’s pribably going on Craigslist and make a few hundred. Let someone else deal with it.

 

[zakkb787]

Strangest thing. Might be fixed. Mom and dad went down and put a new gas cap on it and reset the computer and somehow the code is gone. And hasn’t came back. Ugh. Damn GM. We will see if it comes back haha

 

[zakkb787]

Well the MAF cod is gone. Now throwing a p0134 for bank one o2 sensor. Yay. Lol hopefully that’s all it is

 

[NC-smokinlmm]

Take it out, spray it with brake cleaner and spray some sea foam into the bung for it. Then go drive the shit out of it...

 

[THEFERMANATOR]

Those system's are DUMB to put it mildly. Excess blowby can trip that code, bad pcv valve, a piece od charcoal caught in the purge solenoid, pretty much anything that alters airflow. I do know the resonator cracking is semi common on those to cause issues.

 

[zakkb787]

Those system's are DUMB to put it mildly. Excess blowby can trip that code, bad pcv valve, a piece od charcoal caught in the purge solenoid, pretty much anything that alters airflow. I do know the resonator cracking is semi common on those to cause issues.

FERM I knew I should have just PM’ed you first. As of now the code is gone. Just dealing with the o2 sensor code. Since it says no activity shown, I’m gonna go ahead and guess that the sensor is just flat out shot.

 

[DAVe3283]

Eh, if you had PM'd him, we wouldn't be getting the good tech details on the forum for everyone to learn from. So posting the diagnostics publicly is better, IMO. Plus I'm interested to see how it all works out.

If the sensor is showing no activity, it could be shot, or there could be some kind of wiring issue. I can't remember if this generation has two banks of cats or just a single cat. If it has two banks of cats, swap the sensors from one bank to another, and see if the code follows the sensor or stays with the original bank. That can tell you if the sensor is bad or not.

For just one cat/bank, probably need a known good sensor to try, or pony up for a new one. I've had ...mixed luck getting used O2 sensors from junkyards. I'd say 1 in 4 work right after getting pulled.

Sent from my Cat S60 using Tapatalk

 

[zakkb787]

It’s got 4 sensors. 2 cats. Was thinking of trying the fleabay ones. 4 for $58. What could go wrong :thumb:

 

[THEFERMANATOR]

Eh, if you had PM'd him, we wouldn't be getting the good tech details on the forum for everyone to learn from. So posting the diagnostics publicly is better, IMO. Plus I'm interested to see how it all works out.

If the sensor is showing no activity, it could be shot, or there could be some kind of wiring issue. I can't remember if this generation has two banks of cats or just a single cat. If it has two banks of cats, swap the sensors from one bank to another, and see if the code follows the sensor or stays with the original bank. That can tell you if the sensor is bad or not.

For just one cat/bank, probably need a known good sensor to try, or pony up for a new one. I've had ...mixed luck getting used O2 sensors from junkyards. I'd say 1 in 4 work right after getting pulled.

Sent from my Cat S60 using Tapatalk

5.7l has 2 cats and 4 O2's, 5.0l has 1 cat but 3 O2 sensor. Swapping upstream O2 sensors is not fun as GM buried the passenger side upstream O2 sensor plug up beside the exhaust manifold inside of a heat shield. If you have big hands(like me), forget getting to the plug with your hands. I used my long needle nose pliers to release the plug and get it released. It always seemed to be the 1 that failed and would wreak havoc. I hated those obd system's, I lost track of how many goose chases I went on working on them. Getting cylinder misfire codes that ended up being an O2 sensor, cylinder #4 misfire codes for failed knock sensors, downstream O2 sensor codes from leaking intake gaskets, spider injection setting too many codes to list, and so on.