I have a 99 GMC Yukon that keeps getting error codes p0101, p0171, and p0174 on my Bosch pocket scanner. It is also experiencing symptoms such as stalling, revving by herself, and sometimes I have to spray starter fluid into the air intake where the housing for the air filter is. Sometimes she won't start or she just wants to drive by herself. Any help would be appreciated
99 GMC Yukon SLT XL 1500 V8 5.7L error codes and symptoms
- Thread starter Roughcutt
- Start date
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east302
Full Access Member
Do you have a scanner to read mass air flow (MAF) and manifold absolute pressure (MAP) sensor readings?
P0101 is set when the air flow readings calculated by the computer (using the MAP sensor) and those detected by the MAF sensor do not match. I'd start with that code first, as the other two are calling out a lean fuel trim condition on both banks and may be the result of the first code.
Check for a vacuum leak in the air intake, a plugged intake, dirty air filter and that the PCV valve is seated. Check the MAF screen, see if it's dirty or clogged up. It could be a bad/dirty MAF sensor or a bad or poorly sealed MAP sensor.
Otherwise, you'll need a scanner to get some readings for a good diagnosis. A Bluetooth OBD adapter with an app (DashCommand or CarGaugePro) should get you what you need.
GM has pinpoint diagnostic tables for each code. Let me know if you want them and I'll post them.
Sent from my iPhone using Tapatalk
P0101 is set when the air flow readings calculated by the computer (using the MAP sensor) and those detected by the MAF sensor do not match. I'd start with that code first, as the other two are calling out a lean fuel trim condition on both banks and may be the result of the first code.
Check for a vacuum leak in the air intake, a plugged intake, dirty air filter and that the PCV valve is seated. Check the MAF screen, see if it's dirty or clogged up. It could be a bad/dirty MAF sensor or a bad or poorly sealed MAP sensor.
Otherwise, you'll need a scanner to get some readings for a good diagnosis. A Bluetooth OBD adapter with an app (DashCommand or CarGaugePro) should get you what you need.
GM has pinpoint diagnostic tables for each code. Let me know if you want them and I'll post them.
Sent from my iPhone using Tapatalk
RicanGM
Full Access Member
East 302, What Bluetooth OBD adapter you recommend?
I looked on Amazon and the prices range from$10.00-$99.00
Which brand you recommend?
I looked on Amazon and the prices range from$10.00-$99.00
Which brand you recommend?
east302
Full Access Member
I used a BAFX 34t5 adapter which is for Android. It was around $30. I tried a Palmer Performance one for iPad at nearly four times the price and couldn't get it to work. A cheap RCA android Bluetooth tablet worked fine with the BAFX.
I should throw out a caveat, though. These adapters and apps don't replace a good handheld unit like a GM Tech2 or the high end versions made by SnapOn and others, but it's a good substitute for getting most readings like oxygen sensor voltages, fuel trims, misfire counts, etc.
DashCommand and CarGaugePro are two that I know work with this adapter. You do have to buy the extended PIDs for your specific vehicle with the DashCommand, but I don't remember having to do that with CarGaugePro. The apps are around $20, the extended PIDs another $20 or so.
CarGaugePro does have a graphing function, which makes it easier to see trends in values, but the user interface is a little clunkier than DashCommand.
I don't think that DashCommand will read the ABS system, not sure about CarGauge though.
DashCommand does read the MAP sensor pressures and throttle position sensor angles which are values used in the GM diagnostics for the P0101 code. Here are the tables for that code for a 1998 350, should be the same or similar for your 99.
These tables are from alldatadiy.com which seems to very closely mimic the factory service manual. An online subscription is about $25/year. It has the diagnostics for each code, repair procedures, wiring diagrams, torque specs, TSBs and other things. It may be worth looking at if you do a lot of your own work.
Sent from my iPhone using Tapatalk
I should throw out a caveat, though. These adapters and apps don't replace a good handheld unit like a GM Tech2 or the high end versions made by SnapOn and others, but it's a good substitute for getting most readings like oxygen sensor voltages, fuel trims, misfire counts, etc.
DashCommand and CarGaugePro are two that I know work with this adapter. You do have to buy the extended PIDs for your specific vehicle with the DashCommand, but I don't remember having to do that with CarGaugePro. The apps are around $20, the extended PIDs another $20 or so.
CarGaugePro does have a graphing function, which makes it easier to see trends in values, but the user interface is a little clunkier than DashCommand.
I don't think that DashCommand will read the ABS system, not sure about CarGauge though.
DashCommand does read the MAP sensor pressures and throttle position sensor angles which are values used in the GM diagnostics for the P0101 code. Here are the tables for that code for a 1998 350, should be the same or similar for your 99.
These tables are from alldatadiy.com which seems to very closely mimic the factory service manual. An online subscription is about $25/year. It has the diagnostics for each code, repair procedures, wiring diagrams, torque specs, TSBs and other things. It may be worth looking at if you do a lot of your own work.
Sent from my iPhone using Tapatalk
Last edited:
RicanGM
Full Access Member
Thanks East302 for the information
I will look into the Bluetooth adapter and alldatadiy, looks like its worth the investment.
I will look into the Bluetooth adapter and alldatadiy, looks like its worth the investment.
o_fatmike_o
Member
did you get it figured out? did you try cleaning the MAF ?
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