PO175 and live data

[Boog]

I'm looking for some diagnostic help please.
My all stock 2006 GMC 5.3 with 175,000 miles is randomly showing PO175 code. System rich bank 2. It runs pretty good but occasionally feels sluggish on take off. No smoke. No other codes.
I looked at the live data on my little scanner and wrote down these conditions.

at idle performance

fuel system 1 CL
Ect 184*
STFT B1 % -7.0 to -10.1
LTFT B1 % -19.5
STFT B2 % -8.5 to -12.5
LTFT B2 % -19.5
Map 11.8 to 12.1
Rpm 550
Sprk adv 18*
Iat 109*
Maf 0.935 to 0.980
Tps 11.3
02s B1 S1 V 0.120 to 0.845
STFT B1 S1 % -7.0 to 9.3
02s B1 S2 V 0.700
STFT B1 S2 % NA
02s B2 S1 V .100 to .835
STFT B2 S1 % -8.5 to -13.2
02s B2 S2 V .585 to .615
STFT B2 S2 % NA

PTO status On

I understand that Maf needs to be around 5 and the fuel trims are off.
What puzzles me is the over rich condition is only on bank 2 so I would think what ever is throwing that code is either a leaky injector or plug or coil issue on that bank. I have replaced the bank 2 sensor 1 some time ago but didn't help. The 175 code comes randomly. It may reoccur in a couple of days and it may not appear for weeks. This is a flex fuel engine but I only run 87 grade with less than 10% ethanol. No work has been done to the engine. I have ran Techron injector cleaner through it numerous times but can't say it helped any. It runs pretty good overall. I'd just like to find the cause and fix it.
Can any of you techs make anything out of this information and offer some guidance for this diy'er?

[AussieinNC]

All points to a bad MAF unit...

I notice idle is really low as well...another sign of bad MAF.

What fuel pressure is it running at...?

[Boog]

I'll have to get that. The pump isn't very old but I know, it can still be bad. I have already cleaned the maf and connector too.

[Boog]

Key on 58#
engine idle 62#

[AussieinNC]

Any chance you have another MAF you can swap in?

[Boog]

I do not, unless my '03 Tahoe uses the same one. ?

[AussieinNC]

Maybe a quick trip to a breakers yard to pick up a second hand one...

All the errors seem to point to a bad MAF....

I wouldnt use the 03 Tahoe one in case there is a system issue causing damage to the MAF...would not want you to become car less....

[Boog]

Good morning.
Well, unfortunately the only jy around here doesn't have anything as new as the 2006 year range and buying a good used maf would be a crap shoot too.
Considering the age of my '06 I might just go ahead and buy a new one and call it preventive maintenance. As for the one on my '03 Tahoe, it's got 265,000 miles on it too so.. I may hook it up and see how it reads and go from there.

[Boog]

Ok, I hooked up the scanner to the '03 Tahoe for comparison and here's what it shows.
Only dtc is a knock sensor PO327

Both trucks use the same Delphi MAF # 25168491
This scan is the Tahoe. I have not swapped the MAFs yet.

at engine idle

Fuel sys 1 CL
Fuel sys 2 CL
Ect 186*
STFT B1 % 1.5 - 3.9
LTFT B1 11.7
STFT B2 1.5 - 3.9
LTFT B2 10.9
Map 12.6
Rpm 668
Sprk Adv 19*
IAT 109*
MAF 1.137 - 1.166, (at 2,000 rpm 2.664)
TPS 18
02s B1 S1 V .065 - .735
STFT B1 S1 % 1.5 - 3.9
02s B1 S2 V .760 - .805
STFT B1 S2 % NA
02s B2 S1 V .100 - .810
STFT B2 S1 % .07 - 3.9
02s B2 S2 V .125 - .725
STFT B2 S2 % NA
By what I have read that MAF reading looks low.

[AussieinNC]

Low MAF readings apart from a faulty MAF are usually due to vacuum leaks...check out all the vac lines for cracks and splits...including the PCV line....

Old lines go hard and start to leak over time...

How old is the air filter?

[Boog]

The filter is a couple years old but not many miles on it.
I would feel better about the maf being bad if there was a maf fault code present but there is not.
And since the only code is PO175 "system rich bank 2" I tend to think it is possibly a leaky injector on the right side. And at the cost of injectors I can't just throw in new ones so I would need a shop to run an injector test on them. My little scanner don't do that.

[Boog]

Update on 06 GMC
After liberally using brake clean and propane I could not find any vacuum leaks and the air filter is only 2 months old. I gave in and bought the new maf sensor.
Less than 3 minutes after restarting the engine and let idle the SEL came back on, same code, but I let it run for a while and monitored the live data. The fuel trims seem to be going down some. Idle speed remains about the same. Maf went down. (I have seen maf measured in grams per second but my scanner reads it pounds per minute). Below is the latest live data after the new maf sensor.

Closed loop
STFT B1 -2.3 (0 to -3.1)
LTFT B1 -8.5
STFT B2 -2.3 (0 to -4.6)
LTFT B2 -12.5 (after idling for 10 min it went to -14.8)
Map 11.2
RPM 552
Adv 18*
IAT 106*
MAF lb/min 0.780

upstream 02s read much like before
Compared to the first data it looks like some improvement.
I will make a 100 mile trip in the next few days and recheck after that.

[AussieinNC]

I would be running a drive cycle and reviewing the results...

General Motors Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

[clinebarger]

It's not just Bank 2....Both banks are running rich!

The MAF sensor is the most common culprit here as an '05 doesn't have a Fuel Pressure Regulator on the fuel rail.

But don't rule out the Engine Oil being loaded with Fuel, I've seen fuel loaded oil cause negative fuel trims & it's usually bank 2 that's worse (More negative)

You can also unpin the Yellow wire out of the MAF sensor connecter, Cycle the key a few times (Gotta let P0102 set!).....Then the engine will run it Speed Density mode, If the fuel trims correct, You have a overreporting MAF sensor.

If this is a Flex Fuel truck? That can complicate diagnostic procedures a little

[Boog]

Well hey CB. Glad you joined in.
This is an '06 if it makes a difference.
I thought if it was running rich on both banks it should have coded for both sides but it only shows bank 2. So I wondered if maybe the maf is sending a signal to increase fuel to bank 2 only, if it can.
As you can see the bank 1 and 2 fuel trims are close.
This is a flex fuel engine but I only run 87 grade and around here we have less than 10% alcohol mix.
I saw where one shop checked the alcohol content in their truck's ecm. On his truck it showed 36% and he blamed it on owners who short fill. Sounds weird to me but he reset the % to 3 or so and his fuel trims corrected. I cannot see alcohol content with my little scanner.
I have not smelled the oil for gas. I'll do that tomorrow.
I had thought maybe one injector might be leaking but when I pressure up the fuel pump it holds. I should probably pull the plugs and examine them.
The engine runs good. The code usually sets while idling for 3 to 5 minutes.
I have also wondered if the bank 2 02 sensor was sending a lean signal calling for more fuel to the right bank in error. ?

[Boog]

As stated above I did replace the MAF sensor and it seemed to be dropping the fuel trims here in the driveway.
This morning it started raining as I was going out to raise the hood so I just took a little trip and tried the relearn as AussieNC posted above. The short trip into town went without a hitch. I made my usual stop and let it idle for bout 15 minutes where it always coded before. All good so far. I ran out on a back road varying speeds and accelerations. It felt a tad bit more responsive and seemed to shift a bit firmer. I guess I drove it around 45 minutes and stopped at the shopping center 30 minutes later. Started up to come home and it coded in less than 2 miles while moving less than 40 mph. Once home I scanned it again and the same old PO175. I let it idle and monitored it for a while and here are the readings. The short terms are down but the long terms are back up to where they were when I started.

Fuel sys CL
STFT B1 -1.5 to +2.3
LTFT B1 -18.7
STFT B2 -0.7 to - 3.1
LTFT B2 -19.5
RPM 550
MAF .850
MAP 11.5
After clearing the 175 code I scanned it again and the PO172 showed up so it was running rich on both banks after all. I cleared it and came inside.
What's the possibility of worn spark plugs causing this? There are no misfires. It doesn't blow black smoke and it doesn't use any oil. Yet. I've got a tight engine.

[Boog]

In my vacuum leak testing I also clamped off the hose to the brake booster to eliminate it as a source.
The oil only has about 1500 miles on it and it does not smell of gas.
Even though this is a new MAF sensor I may pull that yellow connector wire tomorrow and see what it does.

[clinebarger]

Check the alcohol content percentage & reset it if it's much above 10%

[richards72chevy]

Originally Posted by Boog

Update on 06 GMC
After liberally using brake clean and propane I could not find any vacuum leaks and the air filter is only 2 months old. I gave in and bought the new maf sensor.
Less than 3 minutes after restarting the engine and let idle the SEL came back on, same code, but I let it run for a while and monitored the live data. The fuel trims seem to be going down some. Idle speed remains about the same. Maf went down. (I have seen maf measured in grams per second but my scanner reads it pounds per minute). Below is the latest live data after the new maf sensor.

Closed loop
STFT B1 -2.3 (0 to -3.1)
LTFT B1 -8.5
STFT B2 -2.3 (0 to -4.6)
LTFT B2 -12.5 (after idling for 10 min it went to -14.8)
Map 11.2
RPM 552
Adv 18*
IAT 106*
MAF lb/min 0.780

upstream 02s read much like before
Compared to the first data it looks like some improvement.
I will make a 100 mile trip in the next few days and recheck after that.

I used two cans of throttle body cleaner and tried the propane bottle I couldn't find the intake leak on my 02 Silverado.I ended up ended up using a squirt bottle with soapy water in it.I drenched the intake manifold with the soapy water until my engine light starting to flash.Changed the intake gaskets and it's like driving a different vehicle.

[Boog]

Thanks for that. My intake gaskets were replaced a couple years ago so I don't suspect them but I did spend considerable time spraying and checking. If they are leaking it has to be on the bottom side I would think.
I think at this point I will find a shop with a bigger scanner to check that alcohol content % and have it reset if it's out of line. I don't want to spend big bucks on a bigger scanner for what few times I need it on my own vehicles.