Chevy Colorado fuel pressure test, P0171 - troubleshoot - 1.15.2022

[@scottycrise9808]

EVAP smoke test

[@villar8777]

Do you know anything about this code po123 throttle pedal position sensor/switch a circuit high

[@CompTechMike]

Hi Villar! Thanks for checking out my Chevy Colorado repair videos. P0123 is one error I never got on my truck. As you noted, it's related to the throttle position sensor. My understanding is that those sensors are inside the throttle body. If it were me, I would first try inspecting the throttle body on your truck. Is it clean? Are there any obstructions on the unit itself? If you take off the air intake tube and resonator box (the big plastic box that sits on top of your motor), turn the key to 'on' but don't start the motor, and have an assistant slowly press the gas pedal all the way to the floor (with the motor off). Do you see the throttle body opening smoothly and moving through its full range, then closing fully when they take their foot off the pedal? One common sign of damage I've seen is where someone manually tried to force the throttle body open with the truck off, which can damage it. So that's what I would try, first. Ensure the throttle body is clean and free of any obstructions and operating smoothly. Spray a bit of throttle body cleaner in there. Also remove and clean any electrical connections (using electric contact cleaner designed for those type of connections). Ensure all hoses and fittings are clean and tight. Also check that there's no obvious sign of damage or binding to any linkage in the area of the gas pedal (although I think those codes are related to the TB itself, it doesn't hurt to inspect the entire system). If none of that works, you may want to consider replacing the throttle body. It's been a few years but it looks like SuperModulation is still selling his ported & polished remanufactured TB's on eBay. You can find his shop here: www.ebay.com/str/supermodulationauctions And here's links to those cleaner sprays mentioned above: www.amazon.com/gp/product/B000M8PYO2/ www.amazon.com/gp/product/B00AF0OFVU/ Hope this helps! Let us know if you figure it out.

[@robertzulanda9466]

Green cap is a evap testing port for a smoke test

[@CompTechMike]

Thanks!

[@johnrichardson2495]

The green cap is to remove. You hook up your Evap Smoke Detector there. You can then check the whole evap system by opening and closing the Purge Solenoid and Vent Solenoid, depending on what you are trying to test and check with your smoker...

[@CompTechMike]

Thanks! I couldn't find that information anywhere online. Good to know!

[@julianoliva2850]

@@CompTechMike thanx dor the help bro!

[@michael85745]

I have a 2005 Chevy Colorado that is coming up with a P0171 error code. I believe the line where the green cap is is to be used for a vapor smoke test machine, for testing for any emissions leaks. If you remove the green cap, there is a screw that can be removed. After that a smoke test device can be connected there.

[@CompTechMike]

Great tip! ☺ Does your 2005 have this line also? I believe on 04-05 (possibly 06) it was the return line for an external fuel pressure regulator. 07 has the pressure regulator integrated with the pump, so my thought was this was a vestigial line left over from the external regulator years.

[@CompTechMike]

Just following up on this thread. After replacing around a dozen parts and running many tests/inspections myself, I was unable to confirm with certainty the cause of my P0171 lean condition. Took it to a local reputable garage that I've used in the past, and they worked on it for several hours. They did multiple smoke tests, inspected the intake under UV light, and ultimately settled on it being a leaking gasket at the intake manifold that only leaked in certain temperatures. Had them replace the intake gaskets on Feb. 14 (total $700 parts & labor), and have not had any more issues with the P0171 (today is Feb. 27). No more check engine lights and I've successfully passed my emissions test. I'm going to call this "case closed", but if I start having any more issues again I'm going to revisit this awful PCV hose setup. This is for where the "dirty air" goes into the intake to be burned, after that little 90-degree elbow piece. Looks like you either need to completely disassemble the intake to get to the other end or cut an "access hole". Terrible placement on this, GM! Image of PCV hose hosted in Imgur: imgur.com/a/7sev46g

[@NFSgamingEvo]

Mine doesn't no have any pressure, could be the fuel pump ?

[@CompTechMike]

@@NFSgamingEvo hi! Yes, if you have zero fuel pressure at all, I would verify that the pump is operating and the filter is not clogged. Check any fuses or relays related to the fuel system. Also check that Passlock is not engaged (this rudimentary anti-theft system disables the fuel system if it suspects the vehicle is being stolen - or a defective sensor in the steering wheel ignition). Good luck, if you get it figured out let us know!

[@NFSgamingEvo]

@CompTechMike thank you for reply, seems like fuel pump is not turning on ,fuses ,relays are good ,passlock shows, but after a few seconds goes away,tomorrow I'll check the fuel filter once again thank you

[@CompTechMike]

@@NFSgamingEvo I would inspect the wiring at the fuel pump as well. The extended cab and standard cab, especially, can accumulate water at the top of the pump that can cause them to rust out (and develop vapor leaks if the O-ring seal rusts). Maybe check for voltage at the pump? They're tricky to reach - either need to drop the tank or lift the bed - but you can inspect them by holding your camera up around the top of the tank. Also, when you turn the key for a second you may hear the pump engage, or "prime" itself. Do you hear that? Is it an 04-05? They have an external filter along the frame rail. 06 model year and up have a filter integrated with the pump. Same with the fuel pressure regulator - early models it was external - later models it was integrated with the pump. Good luck!

[@NFSgamingEvo]

Ok, first thing is first, the truck runs good again! This is what happened to me on Sunday: I stopped at a gas station to refuel. After refueling, the truck started and ran roughly, then shut off. I tried to start it again, but I only got a clicking sound. I thought it was the battery, but it wasn't. Then I connected a scanner, and it threw two codes: P0340 and P0365, which are for the camshaft position sensors. I went to the auto parts store and bought two new sensors, one for the exhaust and one for the intake. After replacing them, the truck now cranks but doesn't start. Good thing I was very close to home, so my brother towed me. I did some tests before ordering a new fuel pump, and yes, it was the fuel pump! I replaced it today because the auto parts store didn't have the one I wanted, so I order online I went with the Delphi brand. Hoping it lasts at least 10 years! 🤞 thanks again

[@CompTechMike]

@@NFSgamingEvo that's fantastic! Glad to hear you got it resolved. How much trouble did you have getting the old one out? They can be tough if it's rusted.

[@codyward8597]

i cant find out where the other end connects to!!!

[@codyward8597]

Can anyone help me plz??

[@CompTechMike]

Hi! Thanks for the comment. I'm not entirely sure I understand your question. It's been almost a year since I recorded this video. Did you mean the line with the green cap? From what I understand, that's a line specifically for performing evap & smoke tests (at least that's what someone told me in a forum, LOL). Or did you mean the other end of something else?

[@codyward8597]

Yes. The other end of the line is disconnected and I’m trying to hook it up but don’t know where it connects to. This is so frustrating

[@codyward8597]

My truck is giving me a lot of issues and idk if that’s the problem or not but would like to figure it out

[@CompTechMike]

@@codyward8597 the other end of which line? Can you post a picture? I usually use Imgur for hosting pictures since KZbin doesn't have native picture capabilities. Alternatively, you might post a picture on sites like 355nation, coloradofans website, or on this Facebook group: facebook.com/groups/1191961547485485

[@csuh13]

My 2007 has been doing the same thing since September. I have also tried everything on your list with the exception of the fuel pump replacement, and I have only replaced the upstream O2 sensor. I also replaced the spark plugs and coils and did a fuel system clean out through the fuel rail. I have been running exclusively premium gas for 2 months now and I've been putting in a can of fuel system cleaner at every fill up. It's also getting pretty crappy mileage in the city. I'm not sure if that's related. It does about 22 MPG on the freeway, but only about 11 around town. Please keep up the great videos! I've learned a lot from them.

[@CompTechMike]

Thanks! And I am sorry to hear you have the same issue. Was talking with someone else on one of the Colorado Facebook groups who also has the same problem. Feels frustrating, like we are just "throwing parts at it" without a definite fix. I'm a bit worried that it's going to turn out to be leaking at somewhere like the rear main seal, but it might also be something ridiculous like the dipstick tube connection to the engine. 🤷 Good luck with yours, if I can figure out anything on mine I'll definitely update the comments on this video. Thanks!

[@kselbe3052]

Had the same code, got a gauge and the KOEO and KOERunning are 38/40 respectively. 2005 Colorado Z1LS 3.5l, i replaced the O2s)up and downstream), fuel regulator, MAP, the PCV hose on the rear of the resonator, plugs, coils and checked the MAP, etc, and everything else spec'd out. Fuel pump it is after the P0171 journey.

[@CompTechMike]

Thanks for the comment! It is a tricky one to troubleshoot, for sure. Glad you got it resolved!

[@julianoliva2850]

well im looking just to know if im ok these past days i do a 17gal aluminum fuel cell swap… below the bed and behind the rear axle put an external bosch inline fuel pump filters an a osias fuel regulator so i wanna know if my fuel pressure is correct also if someone connected tha fuel line gauge to the cluster ? and the evap system is there something we can do? thanx

[@CompTechMike]

Hi! Thanks for the comment. Unfortunately I think this kind of question is a bit outside the scope of something that can be replied to in a KZbin video comment. If you're asking "is it something you can do?" -- sure. I mean, technically you can do almost anything. I've seen plenty of people swapping frames, putting LS engines in their first gen trucks, etc. Almost anything is possible with enough time & money. 🤣 Personally I don't think I would put a fuel tank there -- you're saying below the bed and behind the rear axle -- are you talking about putting one where the spare tire is? I'd have some safety concerns about putting a fuel tank in that location, but it's your truck. As long as you pass whatever emissions and safety laws are in your state, go for it. My recommendation would be to start a thread on the forums 355nation and coloradofans.com. There may be people there who've done this type of mod in the past. Also on the Facebook group "Chevy Colorado & Canyon (First Gen) Fan And Owner Page" -- facebook.com/groups/1191961547485485 Good luck!

[@CompTechMike]

Hi! I could use some help troubleshooting an issue. 07 Z71 I5 with 225,000 miles. I'm getting an intermittent P0171 "bank 1 system too lean" engine code. I had my fuel pump replaced about a month ago due to a P0442 "small evap leak" -- the top of the fuel pump and lock ring had completely rusted through, causing an evap leak and gasoline odor. Since having that replaced I'm not getting the P0442 anymore (which is good), but about two weeks later started getting this intermittent P0171. I had a shop do the pump. I've done a few in the past but I'm getting old and this one was too much work to do by myself. Before I take it back to the people who did it I wanted to try a few other things, first. Including: - Air filter is brand new - PCV hose (that 6" hose between the top of the engine and the resonator box) is brand new - MAP and MAF both replaced - Cleaned throttle body - Changed oil - Ran a couple tanks of "premium" gas through the system - No detectable vacuum leaks. Sprayed a whole can of throttle body cleaner around the throttle body & intake, no change in RPM's - O2 sensors are less than three years old Issue only occurs at highway speeds 50+ mph. No abnormal hesitation, stalling, etc. Just the code. Although my "gut feeling" is that the engine lacks "pep", but I also attribute that to age and high mileage. Fuel pressure "seems" okay. Holds at 50 psi with key on, engine off. Fluctuates between 56-60 psi with engine idling, steady 58 psi at 1500 rpm. You can see the results in this somewhat rambling 5-minute video. Obvious answer would be "take it back to the people who did the fuel pump". Should the pump be putting out higher pressure than shown in this video? Or might it be something else, could be something like a clogged cat causing the lean condition? Maybe I should replace the O2 sensors again? Or should I break out my big code scanner to try to figure out fuel trim readings? 🤣

[@richardholguin8392]

My 2010 chocks and wants to stalls after second gear I can't figure it out regulater or o2 senser

[@CompTechMike]

Hi! Thanks for the comment. Could be a lot of things. Maybe a clogged cat or low fuel pressure? Have you done a fuel pressure test? Are you getting any codes? How many miles on the truck?

[@michaelechivester6478]

Ok mike really like this video. I think Im having a fuel pressure delivery problem on my 2004 Colorado. This engine fuel pressure is around 42psi. Spec is 50-57psi. So this is 8psi below spec. I have not done a fuel pressure regulator test ,but wiil soon. My question is about the pcv valve. I saw a picture you posted, and the cut out someone did. Did you do that cut? Does the cut go thru the intake manifold? Were the zip ties already instslled from factory? Im wondering if a vacuum leak could occur at that location? I already smoke tested the intake manifold, and no leaks. Im slso wondering if i should smoke test the crankcase for leaks. Would leaks in crankcase system cause a vacuum leak?

[@CompTechMike]

Hi Michael! Thanks for checking out my video. Sounds like you've got a lot going on. Regarding the fuel pressure being low, I think the truck will still run at 42psi, however if the pump is having trouble building pressure you may experience starting problems or performance issues with the vehicle at speed. I agree - since the regulator is external on the 2004's it should be tested and/or replaced. I would also inspect the fuel pump if you haven't already. The pump location (especially on standard cab and extended cab vehicles) is pretty bad, in my opinion, since it allows water to become trapped on the top of the tank and rust out the lock ring sealing the pump. Since it can be tricky to inspect the pump, one thing I've done in the past is put my cell phone on video mode and wave it around over the top of the fuel tank - just to give yourself an idea how much rust or corrosion may be going on up there. Are you getting any evap leak codes or smell of gasoline? Regarding the PCV system, the most common point of failure on these trucks is the larger diameter rubber hose running from the top of the valve cover to the bottom of the long plastic box sitting along the top of the engine. Another common issue is for the ports in the top of the intake manifold to become clogged. Sometimes they can be cleaned out with a spray cleaner, other times you may need to remove the valve cover to clean them. Here's the diagram of the PCV system I believe you're referring to: imgur.com/a/wGn6whu There's no "valve" per se, just hoses for "clean air" (going from plastic box to valve cover) and "dirty air" (going from valve cover to intake manifold). And here's the picture of this "cut hole". Note that this does not go into the intake manifold itself, but only through the sound baffle / cover, to give access to the 90-degree bend where the hose connects to the intake manifold: imgur.com/a/JIJ4KxP Sometimes you can test if the hose is broken/damaged/disconnected inside here by a smoke test or by spraying a bit of throttle body cleaner from the back (where the hose disappears inside the plastic cover) and listen for any change in RPM's. Imo it's a pretty bad design, since the only other way to get this off to inspect this section of hose involves removing the intake manifold. Another idea is to remove the entire cover. Sure, it may be a little louder, but definitely easier to inspect in the future. Here's a thread with some additional diagrams and pictures that might be helpful to you: www.355nation.net/threads/intake-manifold-covers.38397/ Good luck, hope this info is helpful to you!

[@michaelechivester6478]

Yes I know about the rust on top of fuel tank , and yes getting EVAP leak code, but it's because the component next to the fuel pump came unglued. It's where the line that goes to canister is. So leaks from there. Thanks for the info, and I will try and post an update of my findings.

[@michaelechivester6478]

You welcome!!!

[@CompTechMike]

Here is a link to "Part 2" in this series. Discussion and some additional parts replaced. Issue not yet resolved: kzbin.info/www/bejne/iZuveoCDaJWnr6M

[@CompTechMike]

Thread on this topic: www.355nation.net/threads/need-help-troubleshooting-intermittent-p0171-bank-1-system-too-lean-07-i5-z71.212541/

[@paultodd4543]

My truck is doing the same. thing I have a 2005 GMC canyon

[@CompTechMike]

Hi! Hopefully we are able to figure this out. Searching in forums leads to a crazy-long list of possible causes. I've posted in the Facebook group "Chevy Colorado & Canyon (First Gen) Fan And Owner Page" and also in the forum over at 355nation. Maybe we can get it solved over there? Here's a link to that thread: www.355nation.net/threads/need-help-troubleshooting-intermittent-p0171-bank-1-system-too-lean-07-i5-z71.212541/

[@gabrielmacias4466]

This video was useless 😕

[@CompTechMike]

@@gabrielmacias4466 it was useful for me. 😊