How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Lou P. Your Own Question
Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 3726
Experience:  building and driving chevy's since i was in the womb!!!! camaro and corvette enthusiest, access to factory diagrams and tsb's
27644750
Type Your Chevy Question Here...
Lou P. is online now
A new question is answered every 9 seconds

I have a 2001 Chevy Tahoe with a 5.3, I disconnected the

Customer Question

Hi I have a 2001 Chevy Tahoe with a 5.3, I disconnected the battery and disconnected the ecm and since putting it back together on start up it idles at 3000rms. I can't figure out what is wrong, I really need some help.
Submitted: 9 months ago.
Category: Chevy
Expert:  Gary replied 9 months ago.

if you disconnect both battery cables for 5 minutes then touch the battery cables together for 1 minute then reconnect both cables to the battery will it still do this ?

is the check engine light on ?

Customer: replied 9 months ago.
I will try that now. No, there is no check engine light on
Expert:  Gary replied 9 months ago.

ok let me know what it does after doing that

and all you did was disconnect the ECM connections ?

Customer: replied 9 months ago.
I was in the process of installing factory electric fans with a dedicated relay box that was built by a company back east. They gave me instructions to put one wire in terminal 42 on c1 and one wire in terminal 33 on c2. They stated that the current wire on 33 could be removed with out issue so I did that. Once I started it and it had this issues I removed the electric fan wiring and put the wire back in terminal 33 and reconnected everything. I did this all with the battery disconnected. One I started it back up I still had the issue. From my understating terminal 33 was for a blend door
Expert:  Gary replied 9 months ago.

ok see if the battery thing helps at all

Customer: replied 9 months ago.
Ok did a timer for 5 min. Now have the cables together for 1 min
Expert:  Gary replied 9 months ago.

ok let me know

if it still does this unplug the computer and be sure all the terminals are clean and tight and snapped into place

Customer: replied 9 months ago.
Ok
Expert:  Gary replied 9 months ago.

let me know

Customer: replied 9 months ago.
Still does it
Expert:  Gary replied 9 months ago.

ok check the terminals in the computer connectors

is this electronic throttle on this engine ?

Customer: replied 9 months ago.
No cable. It's a 2001
Expert:  Gary replied 9 months ago.

ok check the connections and double check for any vacuum leaks at all

Customer: replied 9 months ago.
Last night I even disconnected the iac, tps, and throttle cable, started it and it still did it.
Customer: replied 9 months ago.
I have searched all over for vacuum leaks didn't find any. It has a cold air intake, checked all connections on it all looks good as well
Customer: replied 9 months ago.
The one thing I am wondering, is the relay set up I have is a negative activated for the electric fans. I wonder if when I plugged it into the computer if it caused a short of any kind. I went and purchased a new ecm last nigh that I have not yet installed because I wanted to see if I could fix the issue without having to use it.
Customer: replied 9 months ago.
I have checked the terminals and cleaned connections with electric cleaner and am putting back together. Why am I being referred to someone else?????
Customer: replied 9 months ago.
What's the deal? I really need help with this. I have 6 kids I have to be able to get around.
Expert:  Lou P. replied 9 months ago.

Hello my name is ***** ***** am a professional here at justanswer and i noticed your question has not been answered yet. I hope i can still assist with your issue. Keep in mind i cannot see , touch, or hear what you may be experiencing but i have the automotive knowledge to assist you in the right direction. Can we do a phone chat ? That would be the best route since you have quite a unusual issue and lots can get lost in translation over the net. Let me know. I can help you fix this. Lou.

Expert:  Lou P. replied 9 months ago.

42 on C1 shows Unused in ecm. And 33 shows recirculating actuator control. And is a dark green wire. Is this what you used ?

Customer: replied 9 months ago.
but now it is back to normal with nothing I. 42 and the original dark green back in 33.
Expert:  Lou P. replied 9 months ago.

C1 is blue and C2 is red is this correct ? Is your wire still in C1?

Customer: replied 9 months ago.
c1 is blue and c2 is red. No the wire is out of c1
Expert:  Lou P. replied 9 months ago.

Ok. So does the vehicle have to be in gear and driving to die ? Or can you rev it in park and it died ?

Customer: replied 9 months ago.
It doesn't die
Customer: replied 9 months ago.
It idles at 3000 rpms on start up and won't drop down
Expert:  Lou P. replied 9 months ago.

Oh my apologies I thought it died at 3k rpm ok so it revs at 3k. Gotcha. So the engine literally idled that high or the dash shows it that high ?

Expert:  Lou P. replied 9 months ago.

Does the scanner you have just read codes or can it read live data ?

Customer: replied 9 months ago.
The scanner I have reads data. It's showing 2985rpms. It will rev past just stays at 3k rpms.
Expert:  Lou P. replied 9 months ago.

What wires did you hook where from the relay. ? Besides the ones that went to the ecm. Explain. The wires from pin 46 went to where and the pin 33 went to where ? Also I want you to remove the intake pipe and turn the key on and see where the throttle blade moves too. Yours is fly by wire right ? No accelerator cable ?

Customer: replied 9 months ago.
No it has an accelerator cable.
Expert:  Lou P. replied 9 months ago.

I'm trying to help you quickly lol for you and me both. My best friends water just broke and baby is on the way so I may have to leave for a bit.

Expert:  Lou P. replied 9 months ago.

Ok so with the cable disconnected from the throttle body see if the throttle body moves itself open.

Customer: replied 9 months ago.
42 goes to a large relay box I purchased from a place back east. 33 goes to the same relay set up
Expert:  Lou P. replied 9 months ago.

Yes but which one was supposed to be the power and which was the ground. On the relay you should have terminals 30,87,85,86. What went to where

Customer: replied 9 months ago.
Nothing else was moved
Customer: replied 9 months ago.
The only wire that was moved was 33. And now it is back in the same spot
Expert:  Lou P. replied 9 months ago.

See if your see if your model has this module. If so unplug it and see if it still revs. It's the cruise control module.

Expert:  Lou P. replied 9 months ago.

I understand what was moved we are on the same page. BUT I'm wondering if you shorted the ecm. That's why I'm asking about the relay. There should be 4 wires coming from the relay. What is the part number of the kit or whatever it was you were trying to wire in. So I can google it and get a idea of what it is.

Expert:  Lou P. replied 9 months ago.

Either unplug that module or unplug the fuse labled " cruise"

Customer: replied 9 months ago.
That is what I think at this point. I think the exam is shorted the ecm
Expert:  Lou P. replied 9 months ago.

Well if the cable is disconnected from the throttle then the cruise has to be taking over in my mind. Is there a cruise cable ? Some models had a cruise cable and others had a electronic throttle body that used a cable as well for the pedal. So I want you to take off the throttle cable again and the air Intake tube and see what the throttle does when the key is turned on and off.

Expert:  Lou P. replied 9 months ago.

Also if you have a new ecm it may not work until it is programmed to your car so it will most likely need to go to a dealer or shop with access to the programming site.

Expert:  Lou P. replied 9 months ago.

Everything I am looking at as far as possibilities leads back to the engine computer. They will have to be what needs changed. That is the only thing that affects idle. Also coupled with the fact that is the only thing you wired into. So I am confident the ecm is the issue. Hope this information helps. If you need more let me know. I'll check back later. Baby is here lol. Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! ūüėČ Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou.

Customer: replied 9 months ago.
We tried a computer out of a buddies truck it does the exact same thing.
Customer: replied 9 months ago.
Has to be something other than the conputer
Customer: replied 9 months ago.
Computer
Customer: replied 9 months ago.
We have literally tried everything including swapping idle air control valves, maf's, even, and tps from another vehicle that runs perfectly fine and it still does it.
Customer: replied 9 months ago.
Ecm not even
Expert:  Lou P. replied 9 months ago.

Oh ok. If you tried another ecm , hmmm. So you never told me what position the throttle goes to when the key is on and off.

Expert:  Lou P. replied 9 months ago.

Also what did you remove to install the factory fans or was it just a relay you were installing , I'm trying to help but your not answering any of the questions I have asked in order to help you.

Expert:  Lou P. replied 9 months ago.

On order for the rpm to be higher than 1500 the throttle HAS to be opened. So we have to check the physical position of the throttle.

Expert:  Lou P. replied 9 months ago.

Are you still with me ??

Customer: replied 9 months ago.
The throttle is closed when it happens. Doesn't move at all. It was a stand alone relay set up to control the fan. All that was removed was the stock clutch fan set up
Expert:  Lou P. replied 9 months ago.

The throttle blade is closed ? If that is the case then the idle air valve must be opened or there is a massive air leak. The rpm cannot get that high without the air fuel mix.

Expert:  Lou P. replied 9 months ago.

Can you start the truck and cover the throttle opening with your hand and see if it kills the rpms or not.

Expert:  Lou P. replied 9 months ago.

I am gonna have to opt out. A Phone call would have been the better solution so we could have face timed or something to help you get this going. At the moment my Neice is about to be born so I have to go. If no one helps out later and you still have the issue message me and I will assist further. Right now I have to go. My apologies.

Customer: replied 9 months ago.
Got it figured out pin 76 for the Iac came out
Expert:  Gary replied 9 months ago.

where you able to snap it back in ?

where did it come out of ?

Expert:  Lou P. replied 9 months ago.

Good news. If you could rate ME for my assistance I would appreciate it. If not I understand.

Expert:  Lou P. replied 9 months ago.

Has every thing been going good so far ?

Were you happy with my assistance ?