The truck was randomly letting me set and had gotten up to about 12 incidences a month. Would always have to wait ten minutes before it would clear and restart. I had just about given up and was ready to purchase a bypass kit for the anti-theft system when I finally figured out a process to trouble shoot the system. Following are my findings.

The same problem of cranking but not starting unless waiting 10-20 minutes in my case was with the anti-theft system. My system had finally gotten up to about 12 incidents per month. If when cranking to start, the computer does not see a valid ignition code, it will still allow the engine to crank and the fuel pump to run, but will not deliver any fuel through the injectors. After an approximately 10 minute delay, it will reset and allow the vehicle to start if it then recognizes a valid code from the ignition. This is a very hard problem to trouble shoot as it is so intermittent. It will probably not show up at the dealers. Most manuals will mention something about the 10 minute delay with the anti-theft system, but will not say that it can occur from using a valid key, and will usually say what kind of display will be on the instrument panel. The dealer will usually start with replacement of the ignition module (cheapest part of the anti-theft system) and if that does not correct the problem, will move on to the body control module. This can end up being an expense of up to $1500.00 or more if both are replaced. Replacement may fix the problem, but it may return after some time. There MAY NOT be any problems with the Ignition Module or the Body Control Module(located behind the kick panel by the passenger door)!! In my case, it appears to have been invisible oxidation corrosion on one of the connectors in the anti-theft circuit. The signals in this circuit are low voltage, low current signals and are very susceptible to any increased resistance in the circuit. Humidity and temperature changes as well as dis-similar metals in connectors can cause a slight resistance over time that will give the computer a false signal that will not allow it to start. Because of wanting to quickly know if I had a component problem, or a connector problem, I elected to eliminate all of the connectors at one time as a possibility, so I started with the one right at the ignition module, unplugged it and re-plugged it about 10 times to wear off any oxidation, then unplugged it and coated the pins lightly with WD-40 as a moisture/oxidation barrier and reconnected it. I then did the same for the plug at the bottom of the steering column, and all plugs at the body control module, except that because these were easier to access than the ignition module plug, I didn't coat these with WD-40, so that if the problem came back, I could then independently one at a time find out which of these plugs was the culprit. Well, it has been a year now and I have been problem free. The only indication of the problem will be that when it doesn't start, and you just let the key go back to run without turning it off, the anti-theft indicator lamp will blink, instead of of being on steady, or a message about the anti-theft system problem will show on the message display. It will not set any codes that will show up on a code reader. You can see when the circuit resets by leaving the ignition on and waiting for the light to quit blinking, or the display message go away, at which point you can try to restart, and most times it will. Occasionally, it will take two or three attempts for it to get a valid signal due to the connection problem (a 20 to 40 minute period). It is still a pain and time consuming to deal with, but it may save the cost of components that are not bad. In my case, I think that if I had left the dealer replace the ignition module, it would have appeared to fix the problem as it would have made a new connection by unplugging the old module and cleaned off some of the oxidation when plugging in the new module and it probably would have worked for another month to a year and then happened again, making it appear that the module was the problem and that the modules weren't holding up, but that the module didn't really have a problem. I have experienced this kind of connector problem with different circuits on other brand vehicles and other electrical equipment in my line of work in all cases of which no component was replaced, but that if it had been, the electrical connection would have been restored because of disconnection and reconnecting making it appear that the component was bad. There have probably been a lot of expensive good parts replaced because of these kinds of problems. PLEASE NOTE: This problem can and does occur in any GM vehicle with the anti-theft system set up this way although connectors and modules may be in different locations. This applies to vehicles that have the code chip in the key as well. Thanks to a generous service manager giving me information on locations of components and information for replacing the ignition module and reprogramming the ignition code without a computer, I was able to troubleshoot my problem without replacing any components. Please feel free to re-post or get this information disseminated for any other troubled souls with this problem. Also note: If the vehicle shuts off while running after starting, then this will not be the complete answer.

I bought this truck from a used car. lot ever since I got it I have had the problem. and when I called the dealership they said couldIn't do anything for us. so I went to Chevy dealership and its not covered under warranty and they said it would cost over $400.00 dollars. It will not start then wait 10 minutes and it starts again. now it will shout down the whole truck while driving it and I'm sick of it. and I want to give it back unless you all can tell me what do do or if there's a recall on the egnition switches.I don't see why I have to pay $17000.00 for a truck that doesn't start all the time. I would appreciate if you could get ahold of me or wife and let me know what to do and see if theres a recall on them. My name is Ron wife is Candy my phone number is 254-773-3620 Thank You

Occasionally after a short stop, the engine wouldn't start. It would crank furiously. This happened 4 times, about every 2 months, but would start after waiting about 15 minutes. The next 3 times this happened I called GM and filed a complaint. They had me take the p/u to a Chevy dealer who did nothing but tell me they couldn't duplicate the problem. After the 2nd trip to the dealer, leaving the p/u all day, the Service Manager told me not to bring it back unless they could duplicate the problem.

The next time it happened (the 3rd report to GM) I decided to try to swap the relay (earlier the 2nd Chevy dealer said it could be the Crank Position Sensor so I swapped it out- no help). Inside the relay housing I easily found the Fuel relay and next to it was the horn relay (exact duplicate). I swapped them & haven't had the problem since (about 1 yr).

This intermittent failure to start (though it turns over) is bitchy; there were no computer codes showing the malfunction. The GM computer showed a history of a body code. At first, it appeared to be a fuel pump problem. That cost $800. but problem continued. The Chev shop thinks it's the anti theft on the ignition switch. They

have to keep the truck until the problem occurs for them. This is after one tow and 2 cabs. You would think Chev would have fixed their anti theft devices after their sorry history with other models. I don't know how long it will take for the Chev dealer to have the problem with starting.

Update from Jan 28, 2011: The Chev dealers' GM service computer was used to clear all the history of the (body/engine) codes from the memory in the Colorado. Next time the Colorado doesn't start the newly entered code picked up by the GM computer will point to the problem. Most likely it is a faulty anti-theft ignition switch. This part is cheap by comparison to other Chev/GM models, quoted at $124. I should have gone directly to the Chev dealer rather than waste time and $800 on a mechanics guess, who didn't have the GM computer to work with, that it was a fuel pump.

Update from Jun 16, 2011: after talking with other Chev Colorado owners, I discovered that the anti theft device has a computer delay on the ignition. It times out the ignition and after a while it will work again. There was still a problem after the codes were cleared, but the time outs were much shorter and eventually went away entirely. Other Colorado owners had the same problem with changing the battery or letting the truck sit for a while. Each time they eventually got it started and went to the dealer to get the engine codes cleared. There weren't any warnings in the manual. The Chev dealer only gave me hints at what the problem was. Meh! what in the friggin hell is going on with that. Spend thousands of dollars and then some tricky ignition time out with not one note about it. Is this Chev's way of making money, getting you to go to the dealer? COME ON!!!

Update from May 12, 2012: It is the anti theft on the ignition. The anti theft times out if you wait long enough. An expensive fix. The small two screws that attach the ignition cost $24. The ignition is expensive as well. Also the fan speed switch failed. Eventually, once you have waited for years, the anti theft on the ignition corrects itself...like oh well I guess we will let you start it OK now, but every so often it gets bitchy and it's "not now dear, I have a headache". What nerd thought up this device, probably invents malware in his spare time.