99 Tahoe turns over - won't catch, won't start PLS HELP!

[maxaz1]

Hi-
New to the list, but I have relied on the knowledge and expertise on these forums for a long time. Our 99 Tahoe simply died last week - luckily, in front of our house. 106000 mi, and no serious problems prior. My husband is pretty good at basic automotive stuff (he restores classics - body mostly, basic automotive), so dragging this truck to the dealer is for him - and I am sure you can relate - NOT AN OPTION. This is what he has done so far:
Replaced fuel filter, checked fire, checked fuel. Fuel pump is working fine. Turns over great. Battery has full charge. Just won't catch - won't even try to catch. A friend checked codes with scanner, found a possible problem with factory security system and/or 4 wheel drive sensor - but his books only go to 98. Can't seem to get anywhere (literally!) on this problem. Any suggestions will be much appreciated! Please help - we need this vehicle, hubby is pretty stubborn!
Thanks,
Maxine

[sprucegoose]

When you say "won't catch" I'm assuming you mean it won't fire, or begin to even try to start?

My guess is that it is the security system. These trucks are prone to problems with that, in fact mine is in that same boat right now. It only does it occaisionally (like last night!) Although at least if I let mine sit for 20 minutes or so it will finally start, because the computer resets the system.

When you turn the key forward to the run position, all the indicator lights run thru a check. The security light should come on continous for a few seconds, and then go out. If this light is flashing on/off while the key is in the run position, this is undoubtedly your problem.

There is an electrical check in the ignition system that somehow senses how your key fits in the tumbler and it has to pass a resistance value somewhere further down the line. If it does meet this resistance (and this can be caused by other connections in the same circuit that have begun to get corroded) it sends it in the failure mode and will not let the vehicel start. I work with an electrical engineer who came from Delphi (they designed the system) and he's going to help me track my problem down soon.

He made it sound like you can bypass the system by just putting a certain resistor between two wires on the system.

[raycorri]

Originally Posted by sprucegoose

My guess is that it is the security system. These trucks are prone to problems with that, in fact mine is in that same boat right now.

He made it sound like you can bypass the system by just putting a certain resistor between two wires on the system.

You could also try this as a way around it. No need to add the remote starter

PASSLOCK I or II DISABLEMENT

The following is a procedure to disable Passlock I or II Systems for vehicles in which remote start/stop system installations are required. This procedure is required because a remote start system will not function with the current Theft Deterrent System (Passlock) which is included on many 1996 and up GM vehicles.

Please note that this modification is intended to be used only in conjunction with the installation of a remote start/stop system and does not provide a procedure to install a remote start/stop system.

CAUSE
If an attempt is made to start a vehicle by a means other than a key rotation in the ignition switch, the Body Control Module (BCM) will interpret this start as a vehicle theft and disable the fuel injectors.

CORRECTION
A minor wiring modification may be made to allow the vehicle to be started remotely. This modification includes adding a switch to allow the customer to select “ON” to disable Passlock or “OFF” for normal Passlock operation.

CAUTION: When this modification is performed and the switch is set to the ON position, the theft deterrent feature will be disabled. When the theft
deterrent is disabled the SECURITY or THEFT telltale will light up indicating that the theft deterrent system is NOT functioning.

PASSLOCK MODIFICATION
Refer to appropriate GM service manuals and/or SVMQP Electrical Guideline Manual for instruction on splicing and electrical connections.
1. Select a suitable on-off switch (see note below) which will be used to disable/
enable the Passlock System. Mount the switch in a location such that it is
accessible to the driver and will not interfere with normal vehicle operation.
NOTE: This is an extremely low current circuit (approx. 7mA), it is therefore very important that a high quality, low energy, fast acting switch be utilized
for this application.
2. Turn the ignition switch to the OFF position.
3. Locate the Main Ignition Switch Harness. GM's Passlock System wires exit the Ignition Switch Tumbler together and then join with the Main Ignition Switch Harness. (See http://www.bulldogsecurity.com/ or http://64.85.6.118/diagrams/diagrams.asp and select your Make, Model and Year for wire colors and clues on the quickest way to access these wires.)
4. Locate the Yellow Passlock Data Wire which is included in a bundle of three tiny (20 GA) wires wrapped in friction tape.
Cut this wire and splice a 0.5mm2 (20 GA) yellow wire to each end of the cut wire.
Keep wire length to a minimum. Route modification wires clear of moving parts.
Connect the yellow wires to the switch such that the contacts are OPEN when the switch is in the ON position.
5. Turn modification switch to the OFF postion (contacts closed).
6. Start vehicle to verify normal operation. If engine “cranks but will not start"
recheck the switch position (contacts should be closed), wire connectors and
modification wiring.

SWITCH OPERATION

To enable remote start:
Start the engine with the ignition key (modification switch must be in the OFF position). Turn modification switch to the ON position (contacts open). The SECURITY or THEFT telltale will light up indicating that the Passlock System is inoperative.
Once the SECURITY or THEFT telltale has been on for at least 5 seconds the vehicle can be turned off and then remotely started.

To disable remote start:
The Passlock System can be reactivated by turning the modification switch OFF (contacts closed). Vehicle can either be running or off when this is done.

Please note that the VCM/PCM will record Diagnostic Trouble Codes (DTCs) related to the security system when the modification switch is in the ON position (circuit open). This is due to the way that the VCM/PCM interprets this condition.

NOTICE
Any condition which removes battery power from the Vehicle Control Module/Powertrain Control Module (VCM/PCM) (e.g. dead battery, disconnected harness connectors, etc.) will prevent the vehicle from being restarted. If the engine exhibits a “cranks but will not start” symptom, place the modification switch in the OFF (contacts closed) position. This will reactivate the Passlock System and allow the vehicle to be started with the ignition key.

Ray

[plumberrick]

these are the same symptoms i have on my 99 tahoe with 26,000 miles. the fuel pressure at the schraeder valve reads 45psi. the car will start for a split second or 2 and die. the pressure gauge will stay at 45psi. i've replace the fuel relay. the battery is a few months old and the 2 positive cables are now clean. there is still a loose feeling between the cables, but all the electronics and starter crank good. the oil pressure gauge does jump up for the short burst of a start.

starting fluid will make the car run for a few seconds that the spray last.

anymore suggestions would be great.

thanks.

rick.

[maxwedge]

Originally Posted by plumberrick

these are the same symptoms i have on my 99 tahoe with 26,000 miles. the fuel pressure at the schraeder valve reads 45psi. the car will start for a split second or 2 and die. the pressure gauge will stay at 45psi. i've replace the fuel relay. the battery is a few months old and the 2 positive cables are now clean. there is still a loose feeling between the cables, but all the electronics and starter crank good. the oil pressure gauge does jump up for the short burst of a start.

starting fluid will make the car run for a few seconds that the spray last.

anymore suggestions would be great.

thanks.

rick.

Double check this, but I believe you need 60-65 psi with that engine.

[plumberrick]

thank you maxwedge for your quick responce. so 45 psi will not keep the engine running? there are no codes on the obd ll.


is the pressure at the schrader valve the high side from the pump, or the low side after the pressure reguator? is a new pump required or a regulator?


thanks.

rick.

[maxwedge]

You are reading actual line pressure, check the specs for the proper fuel pressure. Take the upper plenum off and see if any fuel is leaking around the injector unit. If it is actual lo press, more than likely the pump is bad, but check the other issues first.

[plumberrick]

i rechecked the fuel pressure and even jumped the fuel pump relay to get fuel pump running without the 2 second initial cycle. the pump puts out 62# to the schrader valve. i removed the #1 plug and wire and checked for spark. ok.

the car will start for a second then die. how do you check the pcm?

rick.

[sprucegoose]

Plumberick,

Does your "security" light continue to flash when you have the key in the run position? If so, I'm sure it is this Passlock System that is giving you grief. I haven't looked to deeply into raycorri's explanation of the on/off switch to disable the Passlock system, but I'll bet this will work for you. I know I need to do this soon before mine goes down for the count!

If someone has a detailed GM service manual, there has to be a troubleshooting guide for the PCM operation in this mode shown in there I would think.

[mobil_12]

The truck starting and dying is a classic anti theft issue. It sounds like the anti theft has gone into fail mode for some reason. Try turning the key to the run position and leaving it there for 20 minutes and then try to start engine. This will relearn the system and if there is not a major failure, the truck will start. If no luck there, bite the bullet and tow it into Chevy.

[plumberrick]

thanks guys, i will try this in the morning and keep my fingers crossed. the security light does stay on with the key in the on position. so you might have the correct theory.

i'll post the good news in the morning.

my wife is tired of all the time i've spent with the car and the forums.

if you need help with any plumbing issues, you will get it from people like you and me at ridgid.com

but now i have another forum here to browse.

thanks again to all that have helped on this and all the other post that i have read in the last few days.

rick.

[plumberrick]

1 more try at this.

i left the key in the on position for 25 minutes to try to reset the passlock security feature. still didn't start. the security light is still on. the car will run on starting fluid for the 5 seconds that i spray it for.

so is it the fuel pressure regulator, passlock, or as my wife says "time to tow it in"

ps. the fuel rail is at 62psi. the security light is on even when running on starting fluid.

thanks,

rick.

[plumberrick]

an update to my 99 tahoe that wouldn't start.

towed the car in to the dealer on thursday afternoon. friday morning the service writer called me with the news.

the v.t.d. (vehicle theft deterant) was not communicating with the system. needed to be replaced and reprogrammed. cost $420. they did give a 10% senior discount to my dad when he asked that worked better than getting a ride to the dealer from my wife.

this is an electronic part that has a plug in connection approx. 20 pin. it's located up under the dash area near radio. the dealer told me that they don't see this problem as much as they see the passlock ignition key issue.

i will try to get chevy to assist with payment as the car has only 26,500 miles and this is a part that should not be subject to wear and tear. p.s the part is made in mexico.

thanks to all that tried to assist.

[erstadmr]

I've been having a starting problem with my 99 Tahoe (71,000 miles) but only on damp days. All I have to do is park it outside on a rainy day and then the "Security" light on the dash stays on when I try to start it. The Vehicle starts and then shuts down right away. The next day (if it's dry) it starts right up. I've had the sensor in the steering colum changed ($475.00) and for the last 9 months I haven't had a problem until two days ago. (the Tahoe usually sits inside a garage) I left it out and it rained overnight and the problem came back. (didn't even drive it in the rain). Took it to a dealership after it started the next day but they said that there were no codes in the computer. They threw water on the engine and said it started to run rough and said that it could use a tune up (but they never said that it would fix my starting problem) I passed on there $400+ tune up. Question: this Passlock Disablement...do you have to have "Remote Start" to be able to modify the Security System?

[ubendover]

erstadmr...
I am in the same boat right now. It just rained and my tahoe will not start, but the "security" light IS solid on now.

I hope to attempt the above and will respond later with the results.