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Aran, General Motors
Category: Chevy
Satisfied Customers: 635
Experience:  Chevrolet Technician
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Chevrolet Tahoe 4x4 I have a 99 Tahoe 5.7 that starts then

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I have a 99 Tahoe 5.7 that starts then shuts down after a second or two. The security light stays on SOLID whenever the key is on. I tried the Passlock re-learn process multiple times, but it still does the same thing - starts then dies a second or two later. I disconnected the C266 connector next to the steering column and it seems I'm not getting any power to the red/white wire pin, which I believe powers the Passlock system (not sure). I've read all the forums and most people talk about their security light blinking. My security light has never blinked, it just stays on solid (with the key on). Any ideas?


how did this problem first start?

tell me how you did the auto relearn?

tell me all you can



Customer: replied 5 years ago.
I have not been using the truck much for the last 6 months, so I start it about once a week and let it run for a bit to warm it up and keep the battery charged. This week when I went to start it, it would start for a second then die. I noticed that the security light was on solid as long as I had the key on. I checked and cleaned all the fuses that say security or engine or ignition on them (under the hood and at the upper driver door). The re-learn process I used was: crank, keep key on for 11 minutes, turn key off for 10 second, crank, keep key on for 11 minutes, turn key off for 10 secunds, crank, keep key on for 11 minutes, tunr key off for 10 seconds. The truck still would not start. I tried the re-learn process about 4 times, same results. Through the whole process the security light never blinks, it is always solid on (while the key is on). In all the forums I've read everyone talks about their security light blinking. Mine is always solid on. Per a thread I read in one of the forums, I disconnected the C266 connector under the dash by the steering column and tested the red/white wire pin (Passlock power lead?) for power with the key on, but could not get the test light to light up. Don't know what to try next. Help!

lets try something da little different here

turn the engine as if you are going to start will start and die......leave the key on until the security light goes should go off in 10-15 minutes...after it gos off,,,,turn the key off,then repeat this proceedure 3 times

this may fix you


Please ACCEPT my answer by clicking the accept button, so I can get credit for my work.i don't receive commission unless you do ..I'm not always going to be giving you good news,so please don't let this stand in the way of you accepting my does not cost you more money.we will still be able to communicate.please understand,i can not see,hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated!if you are not satisfied with my answer,please do not leave bad feed back,i will gladly opt out and let another expert handle the question.if i have sent any diagrams,please print them.they will only stay on here for an hour or so.PLEASE ASK IF YOU NEED MORE HELP

Customer: replied 5 years ago.
That's what I did already (that's what I meant by 'crank'). I have left the key on for over 4 hours straight and the security light never goes off.


i will opt out,,,one of the other guys will be right with you to help you with this...someone will be right with you

Customer: replied 5 years ago.
OK, I'll wait to hear from someone else.
Customer: replied 5 years ago.
Relist: Other.
Expert could not answer my question.
Hello, I'm Aran. I will try my best to answer your Chevy question and make this a positive experience. Your COMPLETE satisfaction is my goal.

These systems are extremely problematic, you can replace one component of the system and then have another component fail and you are back to the truck not starting again. The replacement of any of these components is very expensive and time consuming.

The easiest way to get past this is to just bypass the whole system. CLICK HERE for a company that sells the bypass kit to install for you to never have another theft related no start condition.

If you have any questions let me know.

Regards, Aran
Customer: replied 5 years ago.
Hi Aran. Funny you should mention the PRO bypass. Since originally submitting this question a week ago, I bought and installed the PRO bypass. Guess what - same result, truck still does same thing - starts then immediately dies. I've been trading emails with their support staff and here's what we've come up with.
1. The green light on the PRO does not come on when I turn the truck's key on, so the PRO apparently is not getting power.
2. They had me run a jumper wire from the battery + to the PRO red wire splice. When I did this the PRO's green light came on, so at least we know the PRO was not DOA.
3. I tried to start the truck with the jumper wire in place, still the same result - the truck starts then immediately dies.
4. They said it looks like the PRO will not help me and offered a refund.

So I'm back to square one. As I described in my original question, the SECURITY light stays on SOLID whenever I have the key on. It never blinks, it never goes off. Can you help?
Hi thanks for the reply, on the install kit did they give you a schematic for installation, I would like to review where it is installed and then possibly back trace wiring, circuits etc. and hopefully come up with a solution.

Any additional information on the wiring or a diagram would be great.

Thanks, Aran
Customer: replied 5 years ago.
The PRO bypass instructions did not include a schematic. Here are the instructions they gave me for installing it.

Disconnect the main wiring harness connector (C266) under the dash to the left of to the steering column, then make the following connections in the harness-side wires near the connector:
1. 3 wire (inline) splice from the PRO red wire to the harness red/white wire in B1.
2. 3 wire (inline) splice from the PRO black wire to the harness black wire in A16.
3. Cut the yellow wire in D3 and then splice the PRO yellow wire to the harness-side of the yellow wire. Leave the connector-side of the yellow wire open.
4. 3 wire (inline) splice from the PRO brown wire to the harness orange/black wire in C4.
5. Reconnect the harness connector (C266).
6. Perform the re-learn procedure.

Thanks, John
Customer: replied 5 years ago.
Aran, I also put a scan tool on the truck. No codes or pending codes found. The PRO bypass guys said it might be the BCM/EVO/IPC, but I'm not sure what this/these are and how to test it/them.

Hi John thanks for the additional information, that will give me enough to go on.

Basically the PRO bypass is only bypassing the ignition cylinder portion of the security circuit, so the information from the key cylinder or PRO bypass module still has to be decoded by the EVO/Passlock module and then it will send the fuel enable on to the ECM or engine computer over the class 2 data line.

Based on the information you have given up to this point, I believe there to be an issue with the EVO/Passlock module. My assumptions are this.... The PRO Bypass is mimicking a CORRECT key value when installed, however if the module is dead or for some reason offline, it will still not communicate the fuel enable password XXXXX the class 2 data line to the ECM and therefore will still not start.

As further evidence of this, in the description of the security system, it says that if the security light stays ON SOLID all the time, that there IS a communication issue between the EVO/Passlock module from either wiring or a bad EVO/Passlock module.

So what we need to do at this point is determine if the Passlock module has all the proper inputs to function such as the powers and the grounds, then we can verify the communication wiring also. If all of those things check out, then by process of deduction we have isolated the culprit as the EVO/Passlock module and it will need to be replaced.
I have NEVER replaced the ECM for this kind of issue, so my initial inclination is that there is an issue with the Passlock module.

First CLICK HERE for the information for us to reference, I would print it out.
  1. Reference the schematic and check highlighted fuses with a test light for power with key on.
  2. Remove the THEFT/EVO module and verify the same powers are good at the connector of the module, do not push the test light in the front of the connector, come from the back so as to not damage terminals.
  3. Use one of the powers to power up your test light and then touch the ground wire and make sure the light lights, this is verifying our ground to the THEFT module is ok.
Check those things and then report back what you have found and we can go from there.

If you need any clarification on anything or have additional questions, just post back here and it will alert me.

Thanks, Aran
One more thing I thought of, make sure when checking the power on the fuses, pay close attention to the intensity of the test light being lit. Meaning if the security fuse lights the test light bright and the gauges fuse only dimly light the test light, then we have a power feed issue on the circuit that feeds the gauges fuse.

Thanks, Aran
Customer: replied 5 years ago.
Hi Aran. The Gauges fuse (#4) lights the test light when I turn the key on. The Security fuse (#21) lights the test light with the key on or off. Both light up equally bright. How do I get the ashtray and glovebox out? I can't tell from the drawing in the document you sent me. (There appear to be links in the doc to show how to take them out, but the links are not hot.)

Thanks, John
Customer: replied 5 years ago.
Never mind. I looked it up online. Next going to get the module out and test the power leads.
Sorry about that, I should be around if any more questions come up.

Thanks, Aran
Customer: replied 5 years ago.
K, having trouble getting the module out. My truck has the remote CD player that the doc says needs to come out first. I've read online that this requires me to pop the dash trim off first. Any pointers? I don't want to break the trim. Thanks, John
Thanks for the reply. CLICK HERE is a video on youtube, It should help you see how the clips release. It is not me and sorry if it is cheesy, I am just trying to give you a visual aid.

Here is the bezel to remove.

Here is the radio and cd player. They have tabs on each side that you just depress down and then pull the unit out.


Thanks, Aran
Customer: replied 5 years ago.
K, thanks. Helped a bunch. Module is now out. I have no idea how to probe that connector. It was a bear just getting it disconnected from the module. Is there any way to have the module tested out of the truck?

Thanks, John
Hi again, short of a internal visual inspection revealing something, it would take wire checking to for sure verify the module is bad. CLICK HERE for one forum that I found, you can actually see shorted components on the circuit board on the long rectangular silver fingers on the end.

So if you do not see any physical issues, there is no way to test it out of the truck. Having said all of this I would still leave the pro bypass module in place, if its financially ok as this will prevent any future issues with the key and cylinder being the cause of the no start.

My hunch is the module is bad. I understand the severe trouble of the location, I do not know how else to test for issues other than with the wiring, then if that checks out we could know by process of deduction that the module is bad.

The only other thing I know to do is replace the module and then see if the security light flashes then goes on solid, if it does, that is a good indication the theft module was the issue, as it never did that before.

for the relearn procedure after replacing the module.

Think this over and let me know.

Thanks, Aran
Customer: replied 5 years ago.
Ok, I am going to try to probe B3 and B8 for power, then try to verify the B1 ground. What is B4 for? Should it light the test light with the key on? From the schematic it seems to be an output, not an input.

Thanks, John
Customer: replied 5 years ago.
Ok, I was able to probe (carefully from the connector side) with the following results:
B8 - powers the light regardless of key position.
B3 - powers the light with the key on.
B1 - good ground lights the light (while probing B8)
B4 - does NOT power the light regardless of key position.

I also inspected the Passlock board inside the module cover. Nothing apparent from visual inspection.

Thanks, John
Thanks John for your help that helps me a great deal.

So now we have verified the powers and ground to the module, the B4 will not light the test light as it is the communication line.

To be 100 percent sure we would need to verify the B4 wire to the data link connector for continuity with an ohm meter which I can give you instructions on how to do.

But all and all it sounds like a bad module.

Thanks, Aran
Customer: replied 5 years ago.
Hi Aran. I guess I'll order a replacement module. Can you tell me what kind of reprogramming I'll have to do? Will I have to take it to a dealer to get the new/used module reprogrammed to work with my truck? (I hope not.) What's your opinion on a new vs. used module? I can get a used one off of ebay for about half the price of a new one.

Thanks, John
Hello John, CLICK HERE for the Data Link Diagram this is the connector just below the steering column. If you use an ohm meter ohm from terminal B4 at the theft module to terminal 2 at the DLC or data link connector. If it is less that .5 ohms it is good.

CLICK HERE for the module programming, it says that the relearn can be performed with out a scan tool.

I honestly do not see why a used one would not work, you can check HERE for a wrecking yard in your area that may have the same year Tahoe and then they will most likely also have the module.

If you have other questions or need clarification just post back here.

Thanks, Aran

Aran, General Motors
Category: Chevy
Satisfied Customers: 635
Experience: Chevrolet Technician
Aran and other Chevy Specialists are ready to help you
Customer: replied 5 years ago.
Hi Aran. Replacement module arrived today ($25 from a salvage yard). I plugged it in, ran thru the re-learn procedures, and the truck fired right up. Yahoo! Thanks for all the help. Now to put everything back together.

Regards, John

Glad to hear of success, thanks for all your help and PATIENCE.


Regards, Aran