04 Colorado passlock/no start

[nj110]

Suddenly my colorado 3.5L developed a problem with no start. Battery and charging system are fine. I took it to my mechanic and was told sometimes the start relay gets a siginal, sometimes it doesn't so they told me it is a computer problem. The passlock light is on sometimes and it steady, no blinking. Seems like alot of people are having a problem with this passlock no start when I googled it, but I do not know where to begin. I did scan it with my scan tool and it showed no error codes. Where do I start? Thanks

[bill190]

For this problem, you would need a GM Factory Service Manual set which would have complete wiring diagrams and troubleshooting instructions (Order from helminc.com or a GM dealer).

Then you would need to be able to understand the wiring diagrams and know how to use a multimeter.

How to use a multimeter...
http://www.google.com/search?hl=en&s...imeter&aqi=g10

Then other than the above, for intermittent problems, you can connect test wires to various points in the circuits and run these to a multimeter next to your seat. Then see what is happening when the problem crops up. If one location good, move wires to another spot for testing.

Don't leave the multimeter in the vehicle on hot days as the heat will wreck it.

[nj110]

I was thinking of trying a used ecu which I see cheap on ebay but apparently you have to get it reporgrammed to your vin number or it won't work. I called a dealership but they didn't seem to want to do the reprogramming since I didn't buy the ecu from them. I also read on the web about a passlock sensor or maybe a key problem or iginition switch problem. I do have a hayes manual for it and read the key does not have a chip in it. I had also thought of running a couple of wires down to the starter for a remote start button like I do when tuning up my old chevies that way I would not get stuck somewhere not starting.

[bill190]

This system is based on the ignition switch and the BCM.

[WestCoastColy]

Most of the Passlock no-start issues are in the ignition tumbler.

I was told by a master tech that if you have too many keys or a heavy keyring, it can put a strain on the ignition tumbler and cause the passlock system to fail.

[javojjaaf]

i had a 04" canyon that this happened on twice. the heavy key chain is part of the problem, but part of it was a first year flaw in the ignition switch. the dealer had to change my ignition switch twice before they got it right.

[PencilPro]

Remember that all your switch signals are low voltage and sent to the BCM. You can check the signal to the BCM when it is working to know what wire the signal is going through and when it acts up check the same wire and see if it's there. If it's not there then go to the switch harness and do the same on the wire with the same color to be sure it's not a wiring problem.

[Jimmiee]

Remember that all your switch signals are low voltage and sent to the BCM. You can check the signal to the BCM when it is working to know what wire the signal is going through and when it acts up check the same wire and see if it's there. If it's not there then go to the switch harness and do the same on the wire with the same color to be sure it's not a wiring problem.

Good post Johnny. A scan tool will quickly pinpoint the problem. There may be a problem with the wires and that would show up on the scan tool.

[PencilPro]

Good post Johnny. A scan tool will quickly pinpoint the problem. There may be a problem with the wires and that would show up on the scan tool.

Scan tools have come a long ways! I knew they would be able to tell if there were wiring problems eventually! All they'll need is part changers eventually! LOL!

[nj110]

How hard is it for me to replace the tumbler? Probably alittle harder then on my 48 chevy pickup! Tumblers are not all that expensive on gm parts direct. By the way I checked both my keys and cleaned them with an acholol wipe and there was alot of dirt on them. It has been working alot better now but I know there is some wear in the tumble when I got the truck last year, so I am thinking if I put a new tumbler in hopefully the problem will be solved.