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Chevy Silverado and GMC Sierra Electrical and Computer Questions


I have a 2000 4WD Chevy Silverado with the 5.3 V8 with 49,000 miles. Today when I was headed home from work I noticed that Service Engine Light was on. I headed to the auto parts store to use their scan tool. I pulled out code P0440 “Evaporative Emission Control System Malfunction”

After a little research I found that it might have been caused by the fact the gas cap was not all the way tight. Is this true? Also will the MIL reset itself if the problem is gone?

What else could set a code P0440?

Thank you so much!



  • repairdogrepairdog Posts: 948
    Have any auto store delete the code and it may also be caused by a hole in the line, bad sensor, purge valve, or vapor canister.
  • I have an 03 silverado that I just dropped a new engine into. The original engine was a 4.8L and I bought a 4.8/5.3L to drop in it. The engine went in and connected up fine, but it is not starting by the key. If i bypass the ignition it will turn over. There is also a light that is on from the dash that has a symbol of a lock. Many people are stating that this might be a computer problem. Is there some kind of security lock, do I have to just reprogram the computer, or do I have to have a new computer put in? Also, if I need computer work, is the dealership/manufacturer the only place to get this kind of work done? Are there independent mechanics that do that kind of work?? Thanks for any help I can get.
    And this is kinda an ASAP thing too .. thanks ...
  • huff94huff94 Posts: 2
    I have a 1999 Chevrolet Silverado Z71. Sometimes it doesnt want to start. After you crank the ignition for a few seconds if finally starts. I have replaced the fuel pump/sending unit, and the filter. Still no luck. Also my fuel gauge is acting funny. When you close the drivers side door, and after the dome light goes off, the fuel gauge goes back up to where it was when the truck was running. I have seen the same posting, but havent seen any solutions. Please if anyone has any ideas let me know.
  • I have a 2006 Silverado LS 1500 WD ext cab, a 6 cylinder with 4 speed auto transmission.

    Everything works fine except when I'm using cruise and doing about 55 and I reach a small hill, the tach jumps to twice the RPMs as the transmission shifts, then the RPMs abruptly drop to normal again. The tach is always in the safe zone.

    The dealer said (without driving the truck) that this was normal, but it's kinda annoying. Is there a problem?
  • rcf8000rcf8000 Posts: 619
    Can anyone tell me how many miles you have to drive after your codes have been cleared, and problems fixed, before you can run through emmissions. I just cleared and repaired air intake check valve(passengers side),and cleared code but emmissions station says I have to drive or wait or whatever, till whenever? I still have to retest, but when?
  • The computer logs how many time and miles since clearing of fault codes. They want to see several cycles for the computer to report any problems. You will have to ask them. But I would think that 5 cycles and 100 miles should be okay for them.
  • fredk2fredk2 Posts: 4
    I have a 2006 gmc duramax diesel 2500hd the change fuel filter comes on the display so I replaced it then did what the owners manual wrote to reset turn on ignition to run wait 5 sec. the push brake and gas peddle down at same time for 10 seconds it is reset but it dont seem to work is this reset by a timer or a senser?
  • Hi everyone,

    Recently, my 2k Silverado 4.8L has been dificult to start when it's hot. I suspected my EGR valve so I disconnected it to see but got the service engine light on now. I know it's not the EGR now but the light stays on.

    I remember my dealer telling me once how to reset this but I forgot. Could anyone help?

  • jnealjneal Posts: 247
    From your description I would have to agree with the dealer.
    Your RPMs do increase when the transmission downshifts but not as much as the tach would indicate. Any sensitive electronic meter will do that given a sudden change in input. It's called overshoot. I don't think you have anything to worry about.
  • jnealjneal Posts: 247
    First, go to AutoZone and they will read the code for free and then you will know what to look for. You should be able to turn the SES light off by disconnecting both battery cables and holding the ends together for a couple of minutes. That doesn't work on all vehicles so not completely sure about yours.
  • Thanks jneal. That's exactly what I did (sort of) I disconnected the negative cable from the battery for about 30 seconds. That did the trick.

    Now I'll have to see why it's so hard to start when the engine is warmed up.

    Thanks again!
  • My 2000 GMC 2500HD 8.1 L is reporting the following trouble codes:
    1)MAF or VAF A ckt range/perf
    2) MAF or VAF A ckt low input
    3)IAT Sensor 1 circuit High Input
    4) Manf Cntrl Veh. Spd
    Idle Speed Control
    Auxiliary Inputs

    I have checked visually for any loose connections or vacuum hose issues.

    Can anyone sugest how to isolate the problem to the root cause???

  • jnealjneal Posts: 247
    #4 is probably caused by one or more of the first three.
    I would check the MAF and the IAT sensor. Either one can cause all the others but I lean more toward the IAT sensor.
  • **UPDATE**

    In regards to my previous posts, I have had my truck serviced and it turns out that the Fuel Regulator was causing a poor engine start up (when the engine is warm).

    Just sharing the knowledge...cheers!
  • I have 2005 1500 silverado and can't find fuse for chime when key in ignition - help!
  • I've been receiving the "battery not charging" message. I've replaced both the alternator and the battery with parts from Pep Boys. The terminal cables are clean. Additionally the voltage gauge in the dash fluctuates up and down at low RPM. Especially if you're running the lights and air conditioner. Any ideas?
  • myz71myz71 Posts: 1
    I just changed my battery and was having similar problems. I took it into the shop today and they informed me that after replacing the battery, I have to start the truck, hold the brake, put the truck in drive and rev the engine to 2000 rpm for 2 minutes. This resets the computer and now mine works fine. I hope this helps.
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