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Jason, ASE Certified Technician
Category: Chevy
Satisfied Customers: 38
Experience:  10 Years in the feild, 8 years with GM, ASE Master Technician, and I love my job!
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I have a 98 chevy 1500 and the passlock security light keeps

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I have a 98 chevy 1500 and the passlock security light keeps going off. the fuel shuts off I took it to the dealer and they couldn't get a reading so they replaced the sensor thinking that was it. It worked for about 2 weeks, than I left my dome light on, and I tried it and the truck wouldn't start again,(security light flashing) I jumped it and it started right up. Later 3 days later it did it again, but I just keept trying it and it started up within 5 minutes? Any thoughts?
You said they replaced the sensor, did they replace the lock cylinder or the ignition switch?
Customer: replied 8 years ago.

Jason-- Thanks for taking my question. They said that the sensor was the most common problem, I asked them about the ignition switch and they said they didn't think that was it. They did mention a passlock module? I was kind of hoping that maybe the battery had something to do with it. They said that the new sensor wouldn't "learn" until they hooked the truck up to a charger, there is no date on the battery but it is a Interstate Megatron 60 month and it looks good. I took the battery in and it tested good and so did the alternator. The problem is I am running out of money and I just dropped 500 bucks for the sensor which didn't fix it. I am hoping that I can get it right and it won't cost me another 500. Thans for taking the time again,


Tom, 500 bucks! WOW! I swear sometimes if I didn't do this for a living I couldnt afford to own a vehicle! Anyway, there are several compnents that are part of that passlock system. The ingition lock cylinder has a magnet embeded in the case so that when you insert and turn the key it passes by a sensor that is part of the electrical part of the ignition switch. The part you had replaced, did they just tell you it was a sensor or did they specify which of those two parts was replaced?
Customer: replied 8 years ago.
They said that it was most likely the sensor. Do you think that If I replaced the ignition lock cylinder it would fix my problem? What do you know about this module that they are suggesting? Anyways, Thank you for your help you deffinitly earned your 9 bucks from me.. Is the ignition lock sensor the next step??
Hi Tom! As far as the module goes, I've never had to replace one. And yes the battery could have something to do with it. These things are kind of sensitive to system voltage and tend to loose their memory or jumble information between modules if the voltage is unstable. First I would check your battery connections and make sure they are clean and tight. The interstate batteries are very good batteries but I have seen them test good and still have internal problems. I don't think thats what your problem is though. I'm still unclear on which part they replaced. Everybody seems to have a different name for the same parts sometimes and information gets confused in the transition. Not to say it didn't have more than one issue. The most common miss diagnosis that I deal with though is replacing the sensor and not the lock cylinder. I've made a habit of replacing both because its hard to tell sometimes which one is responsible for the failure. What happens is the magnet that the sensor uses as a signal gets worn or develops a crack in it preventing the sensor from sending the right information to the module. The magnet I mentioned is embedded in the lock cylinder and gets damaged from years of turning the key. Oh, and believe it or not I've seen a heavy key chain cause problems with those systems. Just wear and tear you know? Had a customer that was in construction and he must have had 3 lbs of keys and other stuff hanging from the ignition and he would have to replace that cylinder about twice a year till we figured out that his key chain was causing it. Do you have an invoice that has a part number or description on it? But yes, If they did what I think they did, the lock cylinder would be the next step. That shouldn't set you back too much more as far as the money goes. But before you do anything else, please see if you can get me that part information so I know I'm sending you in the right direction. Positive feedback is important to me so I want to make sure we got this right. I would like to try to build myself as good a reputation on this site as I have here in my hometown. I'm an honest person and I promise I will do what it takes to make sure you feel your money is well spent here. Thank you so much! Looking forward to hearing from you.

Customer: replied 8 years ago.

She replaced all of Part number 26049449, She (the dealer) has finally concided that you may be right and it is the ignition module although she thinks it might be the "wire (part) that connects the 2", $367 bucks. She says that if it were the ignition lock cylinder that I would have a check engine light instead of a security light, I would like to point out the fact that the other dealer in town agree's with you. You already got my best feedback thank you for your additional thoroughness

Hello again! I just looked up that part and thats what I thought you were describing. I have seen many problems with the electrical part of the system she is talking about but I would still replace the lock cylinder first. What she said about the lock cylinder setting the check engine light is not always true. It will set a code but the ECM sees it as a low priority or a "B" code if it is still allowing the engine to start and not request the light to be activated. It will set a code that says that the "security data is incorrect but valid" and allow normal engine operation and set the security light only. This is why I think it is the lock cylinder. Usually if it is the electrical part she is referring to it will not send the passcode to the ECM and the vehicle will not run. This makes me wish I was there to run the tests myself. There are ways for them to check it so they are not guessing with your money. Sorry, I have a soar spot for people that aren't willing to do their jobs. The tests are simple and don't take much time to run. Anyway, if I can be of any more help please ask. You are very welcome! I will be right here if you have any other problems. Oh and if you are satisfied with my advice please don't forget to click ACCEPT. Its the only way they will pay me for my time. Also you will still be able to contact me after the fact. I will keep the question open as long as I can. Thanks again!

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One more thing. You will be able to leave me feedback on the site after accepting the answer. There will be section that will prompt you to leave feedback for me. Thanks once again!