P0174 Trouble Code?

Tiny
HAMMY129
  • MEMBER
  • 2004 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 54,000 MILES
Hi, My truck seems to have a misfire all the time but more so under a load such as when it's stopped at a stop light. The scan tool first gave a code of P0300 P0174 replaced the air filter and cleaned the MAF (now only P0174) with only minor results can't seem to hear or find any vac leaks. The guy at Autzone told me to change the coil pack but I would like to narrow it down a little more before I start replacing parts.
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Thursday, February 5th, 2009 AT 3:43 PM

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Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0174

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)
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Thursday, February 5th, 2009 AT 3:47 PM
Tiny
SIMON1974
  • MEMBER
  • 4 POSTS
  • 2003 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 80,009 MILES
Im Having Lean Codes set on my Suburban, I have changed the MAF sensor as it intermittantly sets this code aswell. I have checked the wiring to the MAF and it has the battery voltage as asked for through Mitchell, I have checked for vacuum leaks at the intake, all vacuum hoses and the intake boot both with brake cleaner and with propane, I have cleaned the fuel Injectors with Champion cleaner introduced into the fuel rails, I have monitored the 02 sensors and they are fluctuating from mid 30mv to 800mv and reacting fast, The fuel trim levels at idle are long term 25% and short term 56.1% off idle they do adjust and at cruise long term go to 14.8%
the Alcohol content is 7% normally and in the freeze frame it shows 0%.
In the freeze frame data I get when the code sets I am concerned with one data aspect that says "commanded gear 6" and when I look at the T.O.S.S it is well above 4000 or 5000 rpm.
I also checked the battery terminals and they were dirty but I have since cleaned them and still am having the problem. I have the entire freeze fram peramiters when the codes set if you want them all I can Give them to you.
Thanks for the help
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
Acutally you did quite a bit of testing, I would check the intake again for vacuum leaks, very common on these vehicles. I would also unplug the mass air flow sensor and see if the fuel trims go to 0 also check for a plugged exhaust this will cause a lean code. Also check the air filter a plugged filter will cause this code. Check fuel pressure and check fuel filter. A plugged fuel filter will also cause a lean code. Check for an exhaust leak that will also cause a lean code. Check vacuum lines for cracks and pcv sys, make sure it's not plugged. Post the freeze frame data and I will look at it. These are some suggestions to check, lean and rich codes are very hard to diagnose because so many things can cause it. Please post back with what you find.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
SIMON1974
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  • 4 POSTS
The air and Fuel Filters are both new, I visually can not see a exhaust leak and I can not hear one, I checked the vacuum lines and they are all in good condition, the pcv system operates good. With a hose to my ear I do hear alot of sucking from near the elbow on the pvc hard line but I can not see a crak or leak under the foam when I inspected it. I unplugged the MAF and it goes to 0.0 on Fuel Trim.
The freeze frame data is as follows.
P0101
Engine speed 1483
ECT 14 DegF
Veh. Speed 0
App Ave 0
acc ped pos 15%
Barometric pressure 28.12 inHG
Commanded Gear 6
Desired idle 1050
Engine Load 5%
Run Time 7 seconds
Fuel Alcohol level 0
Fuel Comp Sens Freq 4Hz
Fuel Tank Pres. SenV 1.61V
Injector PWM Bk1 and Bk2 6.38
Long Term Trim Bk1 and Bk2 13.3
Maf 11.67 g/s
Map 10.34 inHg
Short Term trim Bk1 and Bk2 0.0
Start up Coolant Temp 14 DegF
Tp andle 14.1%
Tp angle Desired 10%
Traction Control Inactive
Trans OSS 4641 rpm

P0171B
Eng Speed 1188 Rpm
Ect 190 DegF
Vehicle Speed 0 Mph
App Ave 5%
accel ped pos angle 15%
Baro 27.90 inHg
Commanded Gear 6
Desired Idle Speed 550rpm
Engine Load 5%
Runtime 3 47
Fuel Alcohol 0
Fuel Comp Sens Freq 4 Hz
Fuel Pressure SenV 1.73V
Injector PWK Bk1 4.21 Bk2 4.1
Long Term Fuel Trim Bk1 and Bk2 25%
Maf 11.96 g/s
MaP 14.47 inHg
Short Term Bk1 -10.9 Bk2 -13.3
Start Up Temp 181 DegF
T.P. Angle 15.5%
T.P. Desired angle 10%
Traction Control INactive
Trans OSS 5121

P0174B
Engine Speed 1168 Rpm
ECT 151DegF
Vehicle Speed 32MPH
App Ave 8
Acc Ped Pos Ind Angle 15%
Baro 27.90 inHg
Commanded Gear 6
Desired Idle Speed 588 rpm
Engine Load 5%
Engine Run Time 2:27
Alcohol Content 0
Fuel Comp Sens Freq 4Hz
Fuel Tank Press SenV2.02V
Injector PWM Bk1 4.14 Bk2 4.23
Long Term Fuel Trim Bk1 and Bk2 25%
MAF 13.67 g/s
MAP 12.70 inHg
Short Term Fuel Trim Bk1 3.1 Bk2 3.9
Start up coolant 117 DegF
Tp angle 16.8%
Tp Desired Angle 10%
Traction control Active
Transmission OSS 5121 RPM
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
Looking I did not know that it had a p0101 code, this changes things, what I want you to do is take the pcv hose off and remove the insulation and check for cracks.I've had 07 silverado's with the same engine has a cracked pcv hose. Also if you can take an exhaust back pressure reading. When you punplugged the mass sensor and it went to 0 that means you are by-passing the mass air which usually means that it's bad, but before you do anthing else I found a bulletin on the p0101. Read it. This message applies to all 1999 through 2004 Chevrolet, GMC, Olds, Buick and Cadillac pick-ups and utilities that are equipped with either the 4.8 liter, 5.3 liter or 6.0 liter Gen 3 V-8 engines. Recent warranty analysis indicates that both the MAF, or mass airflow sensor, and the MAP, or manifold absolute pressure sensor, are being replaced for a MAF sensor code P0101. The cause may actually be a MAP sensor failure causing the MAF sensor code. One of the MAP sensor's primary functions is the calculation of the speed density formula, which is compared to the MAF sensor reading. Should the MAP sensor fail, the PCM may interpret this as a MAF sensor concern and set a P0101 code. If diagnostics are followed thoroughly the technician may find a MAP sensor failure causing this condition. In conclusion, when a MAF sensor code of P0101 is found the technician needs to verify the proper operation of the MAP sensor before concluding that the MAF sensor requires replacement. The fuel long term fuel trims should be -10 to +10 but as close to 0 as possible. You said you replaced the mass air before, see if you can get another one you might still have a bad one. Post back with what you find.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
SIMON1974
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  • 4 POSTS
I did all of the above, I rechecked the PVC hose and it help vacuum for the last 2 days at 19 inHg but I did put a new hose on and it seems to of fixed it, I dont know if maybe it is the rubber hose on the ends.
For now it seems to be running good, thanks for the help
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
CHUCK HOWARD
  • MEMBER
  • 4 POSTS
  • 2003 CHEVROLET SUBURBAN
  • 130,000 MILES
My suburban, z71, vortex 5.3L engine, blew a catalitic converters. This was shortly after a puff of smoke, that dissapates quickly comes out of the exhaust, the converter goes, check engine light goes on, etc. AFter its fixed, a check engine (running lean) light goes on, and then goes back off.
Now, the puff of smoke just came out again, no check engine light, but the codes say that its running lean.
-Some people say it could be a pcv valve that would leak oil into the exhaust.
-Others say, it could be a cracked intake manifold, or the intake manifold gasket.
When I look at the intake manifold, it does appear to either have a portion pushed down that would be a stablizer on the passenger side of the manifold, but aside from that, can't really tell.
When the engine starts, generally all good, just a small amount of liquid exits and drops to the ground when its started.
--On a side note, I was confused on the starburst showing on the air conditioner, apparently when starburst is on, that means that the ac is off, I have not had it on most of the time, so the AC unit compressor was actually on, despite the fact that its pretty cold outside.
Any ideas on my mystery problem? I really hate to blow another cat converter again, particular if I'm going to travel a few hundred miles. Last time it went, I couldn't even power up a hill & it had to be towed. P0171 and P0174 codes
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
Thats great glad I could help.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
What codes is it to be specific? Check fuel pressure. And it may be an air leak in the exaust prior to converter. We need the code.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
SIMON1974
  • MEMBER
  • 4 POSTS
Not so Lucky. It has come on again the Fuel Trim looked fine. Im thinking of doing the intake as I have no Idea what else it could be.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
CHUCK HOWARD
  • MEMBER
  • 4 POSTS
Yes, there is an exhaust leak right now, because the mechanic didn't weld the piece together, he c-clamped it for right now, and has to get another clamp to stop the exhaust from leaking so that it runs more quiet. So, yes, that is confirmed for the exhaust leak before the converter.

I can get the codes later on today, as I have it written down at work. The codes originally said it was a "mass air flow" and either an o2 sensor or cat converter, and the mechanic fixed the cat converter. Does this provide info enough or do you need the actual codes, which can get later today at work?
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
BRIAN 1
  • MECHANIC
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You said the fuel trims looked fine, what were they at?Only other thing I could suggest is take an exhaust back pressure test if you can. Check the o2 sensor connections for water intrusion. Last thing clean the fuel injectors AT THE RAIL. One other thing, you might have to have the injectors themselves tested also. I had the same problem with my wifes G6 and I did all the same testing you did and went round and round, finally I figured out what it was, I had to replace all 6 injectors and it fixed it. But I'm not saying this is the problem but I would not rule it out. Post back with any other questions. Thanks for keeping me updated.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
CHUCK HOWARD
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  • 4 POSTS
Also, thanks for your help, very much appreciated, you guys are great and what a nice cause giving back
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
We need the actual codes and the ones that are current not the earlier ones.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
JOHN KESLER
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  • 1 POST
  • 2003 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 55,000 MILES
Trouble code P0174 displayed. Where to start to correct problem?
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0174

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)4
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
CHUCK HOWARD
  • MEMBER
  • 4 POSTS
PO 171 and PO 174
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
Those are lean fuel on both sides of engine, check your fuel pressure it should be 55-62 psi unless it is a vinZ then it shoudl be 48-52 psi. If fuel pressure is ok check for a vacuum leak.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
JD043053
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET SUBURBAN
  • V8
  • 2WD
  • AUTOMATIC
  • 121,000 MILES
I couple years back I started getting alot of 0174 codes (occassional 0171) on first start in the mornings. I live in the Arizona desert, and it does sometime does get near freezing overnight. This never is a problem in warmer wheather or after running engine to oper temp.
I replaced the MAF sensor and housing. No change. I had a a very good troubleshooting mech go over it. He said the code history shows that it only throws these codes for a few seconds thus making it rather diffucult to trouble shoot an very much intermintent condition.
I just keep clearing the codes when they come up through the winter, but would really like to get the prom fixed.
I strongly believe that this is an issue of engine computer not knowing the outside temp. There is a sensor bulb in the MAF housing. Is this a temp sensor. Any way to test it or replace just it?
Any other ideas or suggestions.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)
Tiny
FACTORYJACK
  • MECHANIC
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I would suspect a leak past the intake gaskets, and it will happen cold when the gaskets are stiff and contracted. Intake air temperature does not play a very large part in fuel strategy, due to it's inconsistent nature, for that changes based on it alone do not occur. The mass airflow sensor on the other hand, does play a larger part, and will affect both banks in most all cases. A check would be to have a scan tool installed to monitor fuel trim, at the very first start with the vehicle as cold as possible. You may be able at that time, to spray some water around where the intake meets the heads, and observe a momentary change in fuel trim, toward a neutral value, and this may indicate that the intake gasket is leaking. The reason I say may, is that it may be leaking vacuum from the underside, and the water may not reach the area. To set the 171 and 174, the fuel trim has to reach approximately 25%, and depending on the conditions, it can be one bank or the other, or as you've seen, both. Of course another possibility can be vacuum leaks on the intake itself, there are not too many sources on this engine though.
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Tuesday, December 1st, 2020 AT 1:03 PM (Merged)

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