Question about 2004 GMC Yukon
2004 yukon denali check engine light stays on, my mech told me a few codes were reset by dealer, so they could sell it. I got 4 codes p01001b, p0171b, p0174b and u1301. Just bought this lastweek drove it 3 times
A code P0100 may mean that one or more of the following has happened:
The MAF may be disconnected, or a wiring connection may be bad, or the MAF may be faulty
Then start with the cheapest, easiest repair procedures:
Verify that the Mass Air Flow Sensor wiring is connected properly and that there are no broken / frayed wires.
Unplug and reconnect the MAF wire harness
Check the voltage of the MAF sensor
Clean the MAF with MAF cleaner
Replace the MAF sensor if cleaning does not help.
Your car has either a P0171, P0174 lean fault code or both stored in the computer, these codes are based on Oxygen Sensor (O-2) readings. A lean code or codes indicate that there's too much oxygen in the exhaust. Remember parts stores have employees that have good intentions but they may not have the experience necessary to interpret what the trouble codes really mean. These codes are based on oxygen measurements in the exhaust. A common mistake with lean codes is to replace the oxygen sensors. This could be a very expensive mistake that will not fix the problem. Especially if both codes are present, because the chance of both O-2 sensors failing at the same time is very unlikely.
Most likely the cause is a vacuum leak. A vacuum leak can be caused from a vacuum hose, intake gasket or maybe even a leak in the air intake hose from the MAF (Mass Air Flow Sensor). Listen for a hissing sound that may lead you to the source of the problem.
Aftermarket air filters that use oil on the element can sometimes damage the MAF. Over oiling the air filter may allow some excess to get on the MAF sensor wire or element. This can alter the reading, fooling the ECU into seeing more or less air flow therefore changing the air/fuel mixture incorrectly. I once worked on a car that would not start that had a problem with a MAF. When looking at the wire in the MAF, there was a burned piece of trash that made it's way past the air filter. After cleaning the sensor the car ran perfectly. The ash that was on the MAF sensor wire was altering the reading by enriching the mixture so much that the car could not run. After talking with the customer, he said the air filter was just changed. This was obviously when some trash got into the air intake hose that settled on the hot wire of the MAF.
According to my code scanner book, P1300 is GM-specific for "Ignition Coil #1 Primary Feedback Circuit".
So I'm guessing that the P1301 is also related to coil/misfire issues and replace that coil and see if it helps.
Before you get started with all the problems, they are all related with the MAF sensor, Clean the MAF first and check the wire harness and all the fuse. There is a fuse for the O2 and MAF sensor, so check that. Good luck and keep me posted.
Posted on Nov 17, 2009
There is no p01001, it's either p0100, or p0101.
Anyway, it's the mass air flow sensor that's bad. The p0171 and p0174 is a lean condition on bank 1 and bank 2, which are the oxygen sensors. Change the mass air flow sensor and that should take care of the p0171 and 74 codes.
The mass air flow sensor can cause the 02 sensors to read lean.
The u1301, is a class 2 circuit short to battery. That, you have to test wires to find with a voltmeter/continuity tester.
I would try and find that short before changing the flow sensor, you don't need the new one shorting out, they are not that cheap.
Posted on Nov 17, 2009
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Posted on Jan 02, 2017
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