Page updated on 04-21-2018

1997 C-1500 security screwed up!

09-30-2010, 10:03 AM
I've got a 1997 c-1500 that the security will not let thetruck start. Ha dthe truck worked on once before. They replace the wiring harness for the steering column and replaced the tumbler. Worked good fra bout two months and started acting up again. security light comes on and it wont start. I f you let it sit for about an hour, it will usually start up and run till next startup. I was told that 1997 had a different security system than 98 and up and that the diode bypass trick could not be done to this truck. Any idea what system this truck has and hoew to bypass it before I loose my mind:banghead:!

10-02-2010, 09:42 AM
Thats odd, my truck has no security system. There is no chip in the key, and copies from wal-mart work. In fact I don't think I've ever seen a security light. Maybe mine has been bypassed.

Does your key have a chip in it? You could try a different key.

Otherwise if it has a chip, it can be bypassed with a resistor. I'll see if I can find a write-up.

10-02-2010, 09:54 AM
As Tblake said no anti theft on 97.
Are you sure on the year 97.
Post first 10 of vin no.

10-02-2010, 04:15 PM
there is no chip in the key like the passkey. We had the truck worked on, replaced the key and cylinder. Security light comes on when the truck wont start. Let it sit for about an hour and It will start (you hope).Tried three different keys with no sucess. We tried the turn the key on for 10 minute trick and it still wouldn't start. the guys doing the work says that the security is a single year type, but all research i've done says that its a passlock. I dont have the vin handy, but can get in a few days. Dont remember date on door.

10-02-2010, 05:00 PM
The key on 10 minutes has to be done 3 times one after the other and wait for security light to go off eack time.
And then try to start it.
Are you sure it is not a aftermarket security setup.
If it has oem security system a good engine body capable scanner sould show code for it.

10-04-2010, 07:46 AM
Maybe try contacting this guy:


10-10-2010, 07:17 PM
Update...went to the neighborhood mechanic after our return home and the truck never failed to start from the time it came on a rollback to the time we arrived. He didn't do anything to it but start it. I'm going to order the by-pass module from newrockies that Chevy-SS posted. If this doesn't fix it then it has to be an intermitten pcm problem. Will post results asap on how the module does. Thanks for the help! VIN is 1GCEC19R8WR108391 09/97 build date model C10753

10-11-2010, 06:28 AM
Your vin shows it is a 98.

10-11-2010, 07:20 AM
WAIT! If your truck is a '98, then do the bypass trick shown below.

Below is from a thread I posted a couple years ago:

My truck (98 Silverado) pissed me off for about 3 months, occasionally doing the same "tamper mode" thing. I tried to use my remote start (or my ignition key) and it wouldn't start, I waited five or ten minutes, and then it started right up.

Finally, I got ambitious and did the permanent bypass on the security wire. I found some instructions on the web. I cut the yellow wire, then measured the cranking ohms resistance at 577. Then off to Radio Shack, where they had 560 ohm resistors +/- 5%. I bought a pack of five for 99 cents. I measured the resistors to find the best one. Closest I could get (to 577) was 554 ohms, so I soldered that one onto the yellow wire (processer end) and into the orange/brown wire.

The instructions said I needed to be within 1% to 2% on the ohms. I was more like 4% off the 577, but the truck fired right up with no problem.

That was over FOUR years ago and the truck has worked perfectly ever since I soldered in the resistor. I fixed the problem for about two dollars in parts!

Here's a diagram showing what I did:

Keep us posted!


Add your comment to this topic!