2008 Silverado P1174
Looking for suggestions on this P1174. A little back ground is we've been servicing this truck for a while now. It has had the p1174 along with p0420 and p0430 for the last couple years but the owner never wanted to fix it until it turned up with a clogged cat. So we get a GM front pipe with the new cats and install 4 new o2 sensors at that time. Denso 234-4668 upstream and NTK 21066 down stream. Test drive and give it back to the customer. About a week later he returns with the P1174. I check for vacuum leaks and then clean the injectors twice with GM top end cleaner. Customer is in a hurry to get his truck back so we stop there! Of course it comes back again! I did a fuel injector drop test and all are the same. We have an Autel Ultra and i graphed both upstream o2 sensors and its pretty clear that bank one is trending leaner. I unplugged both front sensors and the bias voltage is 4.5 on both banks, so i am assuming the wiring to the pcm is ok.
Im thinking of installing GM front o2 sensors or maybe swapping fuel injectors from one bank to the other.
Any other ideas?
Also Fuel pressure with KOEO is 58lbs, engine running about 55lbs. Fuel trims during test drive are apprx -15 to -18 long term and fairly even on both banks. Short terms are lower and cycle neg or positive around 0-5. I guess i'm having trouble figuring why if the code P1174 is for a lean imbalance then why are my fuel trims negative? I always thought if its negative then the PCM is reducing…
Also i had reset fuel comp to 5% it had crept upto 17% , but that didnt do anything to help
Hey Danny, I looked up the P1174 and according to SI that represents lean OR rich condition on bank 1 Considering the trims are negative and on both banks it does sound like its going rich To verify fuel control how about causing a vacuum leak or pumping the brake pedal rapidly to force it leaner while monitoring STFT for enrichment response Did you check the freeze frame for the 1174 to see…
I think swapping the injectors bank to bank might be a good idea. There is also a bulletin for PCM reprogramming for the 1174 code. So before swapping injectors I would give that a try first. One last thing to check would be for a leak in the pipe between the o2 sensors, with a new pipe and cats from a high quality source like GM it shouldnt be an issue, but it is probably worth a look. You…
We did updated the pcm with the latest calibration when we did the cats. I had another tech block the tail pipe and we checked for leaks upstream from the B1 sensor and nothing found. It did have the P1174 even before the cats were installed
Put the 5 gas on the tailpipe for true lambda, that is where you start.
Maybe add propane to the intake and see how you rear O2s react . I'd be curious of they got more negative or switch to positive.
I can try propane tomorrow, i had been using brake cleaner with no change to o2 readings
I was spraying the intake with it looking for leaks. are you talking about adding the propane to the throttle bore?
What was the pressure drop on the injectors? Also is the truck equipped with hydroboost or a vacuum booster? If it has a vacuum booster try blocking the line and see if any changes are made to the trim
The test was done with the tech2 and if i remember it was an even 16lbs on all 8. truck has a vacuum booster, i will clamp that off tomorrow and see if the banks even out.
Also try swapping the downstream o2 sensors. Are there any exhaust leaks present?
Since it was there before you affected repairs, maybe scrutinize exhaust manifolds and gaskets.? Seeing how your trims are fairly balanced bank to bank, I wouldn't bother swapping injectors. Get the fuel trims under control and you'll probably quell that code. I've seen many Ford s set a 171 while bank 2 fuel trims where almost as lean, yet never set a 174, so again, get your trims under…
When the vehicle is cold ,all the way cold like over night get a metered propane bottle your scanner and check the intake plenum if its the one I think they have orings on the bolts that will leak only when its really cold plus the plugged cat should be your first clue that it might have a vacumn leak at the plenum, I would change the plenum gaskets and bolts with new orings napa has a felpro…
Pcm should be adding fuel because of a lean condition! when it had a plugged cat, it was bank 2 that was clogged
Oem sensors only. Trust me I have been here. Ntk are good but oem in upstream for sure. Seen this more than once.
Hi Danny, I work on euros mostly but have a twenty years old suburban with a 5.3L engine and have noticed it has a MAF sensor. Not sure but If yours have a MAF sensor take a close look at the readings. A bad MAF would cause all sorts a problems including things that don’t make good sense like lean or rich fault codes on one bank only. At idle with engine at operating temperature it should be…
Hope you remember to clear adaptations to reset fuel trims to zero after each new attempted repair.
This code is usually set from injectors having an issue. The O2 sensor voltages are learned over time, and if the bank in question gets too far out of the range, then it needs a set of injectors. OEM sensors only, no AM crap allowed, since you changed them with AM stuff. That may just fix it for you. Otherwise, the fuel trim imbalance is caused by the individual injectors on the affected bank…
I agree with you, after market parts are “mechanical suicide”
I didnt get a chance to get back into this truck today, just busy on other stuff. i have been trying to get oe front sensors but getting some resistance from the parts guy.
We got a chance to try a few things today on it. I swapped the injectors from bank to bank and did the same for the upstream o2 sensors, reset fuel trims. P1174 came back after an hour drive. We installed OE GM o2 sensors both upstream and down stream on both banks. Test drove it for about 30min and so far so good. The front sensors were switching alot faster the the NTK were. The day came to…
I agree with a disconnect on the MAF. Disconnect it, let it start/stall, and restart it to see what the trims are doing. If the trims normalize, you have a mass airflow calculation error.
While that was an accurate test method years ago, in most/many cases, on later models, it simply puts the vehicle into a default mode, resulting in very rich trims…makes it almost useless for diagnosis…
Skimmed through the other replies sorry if repeated… had this on my dads. Fix was gm front o2s. The ngks I put in had slightly less amplitude than the gm ones. Even if I swapped the front o2s bank to bank it only set for bank 1
FYI only, i do know from my experience the fuel rails will collect trash at the back and create a problem, if you do this check knock sensors for water intrusion and follow bulletin repairs
The truck is back with the customer. We put new OE GM or sensors in it and drove it for 30min and no P1174 yet. We will find out after the customer has it for a few days. But the o2s sensor reading were alot more active with the OE compared to the NTK
This was my findings as well with my dads truck. My confusion was that it never set a code for bank 2, even when swapping the sensors. Made my life difficult 🙃
The trims were close to zero, maybe +3 or 4. I had cleaned injectors, swapped them side to side. Swapped ignition, cleaned the valves and intake. I was lost.
Well Im going to call this truck repaired with new OE o2 sensors. Customer has had the truck for 10days and hasnt returned with a complaint.