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Chevy Colorado and GMC Canyon Electrical Problems



  • I have a 2004 GMC Canyon 4 dr and I have experenced this problem. I am in Minnesota so its cold here 5 months out of the year. I did some trouble shooting and this is what I found on my vehicle. My problem was in the drivers door control assembly. I have a schematic of this assembly. I took it apart and checked for water damage and it looked good. If you take the switch apart (seperate the two halfs) there is a small black sealed relay labeled RLY3. This is a relay that runs the auto down feature for the drivers window. It also contols the door locks. I did a GMC repair and tapped it with my finger and it started working!!! I am going to keep an eye on this and will keep you posted. I checked with the dealer and its about $200. (not in stock) I did check my BCM for water damage and mine was ok. I checked GM's TSB's and that was a problem with the 2005 models leaking water from the cowling area. I could not find any TSB's on the fuse box issue.

    Thanks SNAPROLL1 for all your comments. By the way, I already hand my cylinder head replaced!!! If anyone needs the information on the notice from GM, let me know and I will get you a copy.

    Happy GMC owner (for now)
  • I could use a copy of the letter i never got one thanks.
  • If I can get a fax number and name, I will send it to you.
  • Dont have a fax will try to get one.
  • I have a 2004 colorado crew cab with the same problem with the locks and drivers window. On dec 26th I decided time for a new battery and which I replaced and that's when this problem started. Could this problem come from just disconnecting the terminals?
    Well thanks to HopeGMC it's working again. I took it apart and looked at everything and things looked OK so I tapped the relay and put everything back togather and wow it worked. A GMC/ Chevy repair......
    My hats off to HopeGMC thanks alot. What is the BCM and TSB. Just for reference I might need later. Thanks again... :) ZIPY
  • Zipy, glad to hear you're up and running again...

    BCM and TSB are acronyms for "body control module" amd "technical service bulletin".
  • Thanks for the info leadfoot4. BCM & fusebox be the same?
  • "Zip", no, those are seperate components. The BCM and the ECM or PCM (Engine Control Module and Powertrain Control Module) are the main computers in the vehicle.The ECM controls the engine's functions, and depending on how complicated the vehicle, it may be just a subsystem of the PCM. The pcm would then control the transmission, transfer case, and in some cases, the rear axle, if it's an electrically controlled limited slip. The PCM also interfaces with the ABS system.

    The power to all of these systems comes from the battery and charging system, via the fuse box (for protection).

    Sometimes I long for the simpler days of "points and condensors"......
  • leadfoot4.......ECM I know. didn't know it was PCM also. This is the first I've heard of BCM. Learning curve..........Thanks.......Zipy
  • ECR223ECR223 Posts: 10
    Thank you HopeGMC. I talked about taking the truck in 2 months ago, but still never found the time, and because my other car has been buried under 2 ft of snow. I tried the relay thing today, and as soon as I put it back in the truck, everything started working again. So you saved me more inconvenience, and probably some money... Well at least for now... But thanks for the tip, it was greatly appreciated... It will be so nice to have power door locks again, AND TO BE ABLE TO GO TO A DRIVE THROUGH, OR ATM....
  • Hi,

    I'm having just the door lock problem (no window problems at all) where my doors will not unlock with the key fob but they will lock with it and the doors lock and unlock normally from inside of the vehicle. The key fob is good because the lights flash when I unlock the doors with the fob but it just doesn't trip the unlock mechanism. Also, if I do not unlock with the fob first, the alarm sounds when I use the key to open the door. Oh, and one other thing that I noticed is that when I remove the key from the ignition, it doesn't unlock the doors. I could have sworn that it used to do that.

    Anyhow, if you have a schematic of the system I would love to get a copy from you. I have the wiring diagram from a car maintenance book but it does not have a schematic... just a wire going in and a wire going out, etc.

    Other than this one problem, the truck has been real good. It's excellent on gas and has plenty of get up and go.

    Thanks for any help.
  • I have a 2006 gmc canyon with a 2.8L. It just now hit 30000 miles. i have had no problems until now and for some reason my brake lights won't light up. The funny thing is that my third brake light works fine. I have replaced the bulbs, checked all the fuses, and have even traced the wiring as far as i can see it but cant seem to find the problem. I contacted the dealer and got the usual BS ($80 per hour) has anyone had the same problem or have any suggestions on what to do.
  • There was a recall on my 2004 on the brake light switdh. You might want to check with a dealer
  • My 2004 colorado stalls for no reason out of the blue. When i try to restart nothing not even a click. Sometimes engine warning light, Sometimes message says REDUCED POWER or TRACTION FAULT. replaced start run relay, did not help.After truck sits 4 or 5 minutes it starts like nothing was wrong. Truck only has 41000 on it.
  • AlennxAlennx Posts: 20

    You are describing exactly what is happening to my 2005 Chevy Col I5 Ext @ 72K.

    The problem is deep cycling the battery kills everything under the hood. I have changed out batteries twice now. First time was at around 55K when the original battery gave up the ghost, massive overheat and death.Second time was an 860CCA battery that lived about 6 months with two accidental drain outs. No, you don't need a "special" battery from the dealer.

    I noticed you said you run a cooler through the ACC adapter. I run a 500W inverter all day in my truck, sometimes engine on, somtimes not. I power a laptop that draws like Vegas and charge camera, radio and cellphones batteries. I've had this vehicle from new and it was fine before I started using it for work. Apparently the regular deep cycling doesn't just 86 the battery but also kills off accesories and ultimately larger parts. My blower is now only working on level 4 (sound familiar?).

    So I spent $200 on a Yellow Optima Deep Cycle Battery and we'll see how that goes. I spose I'll have to replace the blower motor.
  • dmathews3dmathews3 Posts: 1,739
    Running an invertor can do damage to the old battery real quick. Thats why RVs with convertors run 6V deep cycle batteries that are made of charge/discharge and then if you let them go below 50% they become toast quickly too. Your lucky it hasn't got your alternator yet with all the drain on the battery makes the alt. run overtime.
  • duartduart Posts: 4
    This truck is having several electrical problems. It cuts out while driving sometimes to the point of stalling the engine.The tach has very erratic movement. The radio sometimes looses its presets and the clock returns to 12:00. The blower fan also acts up with only high speed available. all this gradually came about overnight. No service codes. All these problems come and go. Sometimes they all are evident, sometimes maybe one or two are showing up. It has never failed to start.
  • AlennxAlennx Posts: 20
    OK, we have the same problem. We are going to figure this out!

    It's not the battery, I just put a new Optima Yellow in and the issues continue the same. It could be the alternator although last I had it checked it was putting out 14V. This was a spot check, not a monitoring over any driving time.

    I am getting an occasional code... "rpm does not match the engine conditions." The suggestion is that the Air Intake sensor needs replacing or there's a vacuum failure. Does this explain the fluctuating rpms? Maybe. Does this explain the blower failure or the under-power while braking? Only if the drop in rpms leads to a drop in charge-back, which in turn drops below 12V. Why is the blower crapped out on 1, 2 and 3, but not 4? Should be the key to the problem but it makes no sense!

    I am going to fit a Voltage Meter and watch what happens while I'm driving. I sometimes get my lights going dim and the revs dropping off under braking, which suggests that there's not enough juice in the harness to power the assisted brakes and keep everything else going... which leads me back to the Alternator. I am willing to bet that anyone who has had this issue has been running larger accesories for a period of time through the two power points and this has knackered the alternator as it attempts to keep up with the over-drain.

    I am also going to get my belt tightened. I'll post as I go.

    Let us know what you try. One thing I do know, The Chevy Dealers I've spoken to have no idea what the problem is and will do fuse-block or computer changes just to charge the **** out of you. I'm calling Chevrolet Corporate right now to confirm they have no idea...
  • Hey guys, your blower fan is just the fan speed resister that's located under the dash on the passenger side. It's easy to replace and costs about $20 or $25 at the dealer. Two screws and a wire plug. When you remove the plug, look at the contacts inside of the plug - look closely. If there is burning of the contacts then you'll also need the harness and you might want to let the dealer fix it unless you are very comfortable with that stuff... The reason that it works on position 4 only is that in position 4 the resister is bypassed and 12 volts is going directly to the fan.

    About the lights dimming when you press your brakes... there was a brake recall some time ago. You might check to see that was taken care of. Also, if you replaced your stereo or added some other after-market item maybe some wires got repositioned and are touching the brake mechanism??? Just a thought.

    Look, I don't work with any car dealer or anything but I know that if you call the service department at ANY car dealer, they are not likely to help you. Why??? Let's put it another way... if you walk into your favorite grocery store and ask them for some free milk, eggs, and steaks do you think that they are going to just let you have those for free? Of course not but yet some people want what the service department sells for free. They are selling their knowledge, experience, and time. They get nothing if they tell everyone how to fix their problems on the phone for free. I know that you and I spent a small fortune for our vehicles but the dealer didn't make the car or the problem. I hate taking my vehicle in for maintenance too but you have to do what you have to do sometimes...

    With that said, I've had a problem with my Colorado door locks for months now and I'm too tight to go get it fixed - I won't call them though.

  • AlennxAlennx Posts: 20
    Excellent heads up on the blower, I'm going to look at that in a minute.

    I found in my research that the MAF is affected by a dodgy alternator or battery. The MAF is attempting to maintain the temp of the hot wire and changes the fuel/air mixture according to the flow & temp of the incoming air, conversely if the power delivery to the MAF is dropping off, it will have the effect of changing the mixture because the hot wire is not as hot and the return signal to the computer is changed.

    I have a new battery so all roads continue to lead to the alternator. I'm going to get me a charge meter... no way some guy is going to line his pockets with my hard earned cash just because he has a family to feed and a mortgage to pay! ;)

    Here's a question... if I had the original battery (1 year ago) and it had to be changed out because it was boiling hot, so hot you couldn't touch it. Would that mean the alternator was over-voltaging the harness in order to charge the dead battery, since the dead battery was now acting as a huge resistor?... and would that lead to cooking the blower (1,2,3), and my CD/radio lights, and my CD player?... and would that lead to permanent damage to the alternator? Tell me I'm wrong, please :(
  • Pollution control Module was defected or shorted out. This was replaced in my truck along with reprograming the Brain. Thank god it was covered under warrenty. Repair would have been aprox. 1,300.00 . Dont plug in power inverters or accessories to vechicle it creates feed back to some electrical componates.My truck now runs fine.
  • Hello, I Have the same problem you have only in a 2004 Colorado, I was just wondering how you went about fixing it?
  • AlennxAlennx Posts: 20
    Just what I wanted to hear @ 72K miles. $1300 repair bill? Thanks ;)

    So, I had the charging system tested at Kragens and with the lights and inverter on and under full load, the alternator was pushing out 14.7V. No other electrical issues detected during startup or engine-off either.

    Get this, the engine light came back on and the engine dropped below 500rpm while he was running the test and the alternator kept pushing 14.7V!!!

    So, according to Kragens, the alternator is fine, the battery is fine AND this morning the blower started working again and my CD player started working again. Tell me that the devil is not at work here!

    The engine is coding that the RPMs are out of range so it could still be the MAF or I could have a vacuum seal break OR the "AIC?" sensor could be jacked... but that doesn't explain the random stopping of circuits, unless the computer is turning stuff off randomly, like when you first start the engine... what if the computer... no... yes, that's it. It has to be.

    There's no over-drain protection on the acc circuits because I've killed a battery twice draining it out over a week by accident. The computer is turning off individual circuits like the blower, the CD player... but the accessory circuits are staying on, WHY! Surely that would be the first thing to go? No, because they are not controlled by the computer whereas the internal circuits, blower, etc are... Outside stuff is my own fault. Makes sense to me. You know Isuzu is selling this truck also?

    So I have MAF cleaner and throttle body cleaner. Next I'll get the AIC? sensor checked and then if there is no improvement after that, It will be destined for the shop. DARN IT! :lemon:
  • duartduart Posts: 4
    I understand the blower speed is controlled by resistors. But this is not continuous. Sometimes the fan and all other problems work fine. When you lose a resistor its over. It don't come back. I am really starting to believe this is a bad ground problem.
  • No - it's not a ground problem if the fan works on High but not the other positions. That's cut and dry - the resister and/or the wiring harness to the resister. Not to say that you don't also have a ground problem. When my resister pack started going out it did just as you said - sometimes it worked and sometimes it didn't. To see why it's intermittent, unplug the plug from the resister pack at the fan motor and look at the contacts and you'll probably see why it works sometimes and not other times. Most likely you'll find one or more burned contacts. The test for the fan is to see if the fan always works on high - if not then look for a ground problem as the resister pack is bypassed in high position.

    Personally, I'd stop looking for ONE reason for your problems because it sounds to me that you have multiple things going on.

    To my knowledge, there's no such thing as a 'drain' sensor in any normal production vehicle. Maybe NASA has something like that but frankly, I would not want it in my car - if I don't want something powered up I can unplug/turn it off without some computer deciding what's best for me. Remember, leave the lights (or other load) on and when you come back to the car your battery could be dead.

    Inverters: I'd never leave one of those plugged in because they eat (consume, waste) roughly 30 percent of the max load even when there isn't a load attached. So... 1000 watt inverter consumes 300 watts of power when not powering anything. 300 watts at 12 volts is 25 amps of current. 25 amps of current for 10 hours is 250 ampere/hours or to put it another way, a toasted battery. Now look at what the inverter does to your car when you ARE using 1000 watts, ie, when you do have a load plugged into it. At full load, it is consuming about 84 amps of current from your car but your alternator can not supply but 60 amps so the other 24 amps comes out of the battery and eventually you have a bulging, burned up battery. Of course, the numbers would be different for different size inverters. And, I haven't even touched on the noise that inverters send back into a computerized vehicle system...

  • AlennxAlennx Posts: 20
    OK, so I'll take the blower problem out of the mix and just get a replacement resistor pack. Good, one down.

    Now, I cleaned my MAF sensor today and it made no difference whatsoever to the way the engine idles. The engine is fluctuating between 450 and 700 rpm at idle so this presumably must be the AIC? sensor or a vacuum leak as the engine light code suggests.

    My 2006 Mazda MPV LX will turn off the outside lights if the key is out of the ignition for ten minutes and the light are left on by accident. It will also turn off the inside lights if a door is left open by accident. That's what I meant by drain-protection.

    If I have everything on in my 05 Colorado with the key turned to ACC, and then start the engine... everything turns off for a second until the engine is running... lights, radio, accessories. That is intentional switching somewhere in the harness. I was wondering if that could be selectively failing some circuits but it doesn't really make sense, especially considering your blower resistors. I guess I just over-heated my CD-player and it needed a while to reset.

    Your electrical consumption figures seem to be generally accurate. My alternator says it pulls 400W continuous, which is 400/12=33A continuous draw against the acc harness and 800W peak draw (66A). The Factory fitted alternator in the Colorado is rated for 100A - 120A. This means that even at full load, the alternator can power my inverter with 35A - 55A spare for everything else and charging the battery (not including voltage drop across the harness and components).

    BUT!!! I degunked my engine bay today and, wouldn't you believe it, I heard a horrendous squeeling noise (above 1000rpm) coming from somewhere on the belt. I checked everything and everything was turning, so I am willing to bet it's the bearing in the alternator. I heard this squeeling occasionally before but I was driving around the mountains in Washington and Oregon states so I figured it was cold and moisture on the belt. Not so.

    Anyhoo, I found a High Output Alternator (200A) for the Colorado for reasonably cheap so I think I'll do that and get a new belt just for s***s & giggles. :shades: -AMPS_W0QQcmdZViewItemQQ_trksidZp1713Q2em153Q2el1262QQcategoryZ33573QQihZ010QQit- emZ200306064612
  • mrwebmanmrwebman Posts: 15
    Sorry, I can't help with the sensors. If you knew someone that had a similar vehicle that you could switch them out for a second, that would be great... Otherwise, I guess you'll have to go by the codes that's being shot and replace sensors one at a time...

    Anything turned off automagically is done so by a contactor (relay). Contactors are pretty easy to test. Either change them out one at a time or swap them around to see if the symptoms change. Mine are located in the relay box under the hood. The really huge ones are outside of that box.

    Your computations for the alternator are close. An alternator is designed to put out 13.8 volts (some actually a little higher). If your alternator is rated at 400W then it's capable of 400/13.8 which is 30 amps. The battery voltage when not being charged is generally 12 volts but can be down to 10 or lower depending on it's charge condition. A 500 watt load (inverter for instance) is pulling: engine on and battery charged: 500/13.8=36 amps; with engine off and fully charged battery 500/12=42 amps; engine off and weak battery 500/10= 50 amps. If you let the battery get much below 10 volts bad things start happening like starters not working and electronics failing.

    On RV's you'll almost always see a separate set of heavy duty batteries just for the inverter. Instead of buying a bigger alternator, I would recommend adding a single deep cycle battery and battery isolation diode assembly to charge it. You can pick up the diode assembly at most auto parts stores or any RV supply house for around $50, maybe less. Wire your inverter directly to this battery with heavy duty cable. By adding this second battery you get several advantages: you'll never be stranded somewhere because of a dead start-battery; you keep most of the noise out of everything on your vehicle because the diode assembly isolates it; and you'll probably save your vehicle battery from premature failure because car batteries are not deep cycle batteries and the constant deep drain and recharge wants to send you back to the auto parts store prematurely. It is a truck so putting it in the bed up close to the cab should work and that keeps the huge wires going to the inverter short thus less $. If you have an audio shop near by they could help you because they do this sort of thing all of the time... you've heard them at the red lights... boom boom boom. The noise drives us all crazy but look at the electronics in one of those sometime - it's pretty amazing.

  • AlennxAlennx Posts: 20
    Yeah, sensors eh? Darn em all!

    All the alternator stuff I've come across rates an Alternator in amps. :confuse: My factory unit is rated at up to 120A... and it puts out 14.7V under full draw from the headlights and inverter and radio, etc... I've seen it with my own eyes ;) This is how I know I don't have a ground fault, otherwise the ground fault would be subtracting from the harness voltage, which appears to be very healthy.

    I fitted an Optima Yellow battery, which is specifically designed for Deep Cycle and is actually warrantied for it (unlike the Optima Red). I have killed two standard batteries in this truck since I started using it for work. the factory battery (570A) died in about a year and the replacement (870A) died in eight months. Clearly the Deep Cycle feature is necessary for my kind of use. I'll post if it fails.

    You know, they build trucks with inverters factory fitted. Are they using a noise-filtered 6V battery under the hood to power it? I bet they are, based on your RV story.

    Anyway, the reality is I'm going to keep using my inverter because I have to power all this crap. My truck is at 72K so things are going to start going wrong on it and now I have to play grease-monkey until my boy passes his test and I can unload it onto him. He's sure to crash it, so then I can buy my new Trailblazer with everything working on it. :shades:
  • dmathews3dmathews3 Posts: 1,739
    They don't make Trailblazers anymore and the few 09's left are getting fewer due to the high rebates to unload them.
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