TurboDSMJ

Alright gentlemen, let me begin by saying my Trailblazer was DOA this morning when leaving my house, and now the back up Z28 which got me to work in this snow is having some hiccups. Below are the symptoms, what do you guess? I am thinking BCM issue or shorted wire.

Car = 1999 Z28, one owner, 99,099 miles, 4L60E, 100% STOCK - New battery/Alt months ago while below issues were intermit happening. Now it is much more common.

1. Sometimes when locking the car with the remote, the VATS will arm and appear to be okay. Walk 30 feet from the car, it goes off until shut off.

2. Sometimes you can disarm the VATS, get in the car, start it, and nothing. No movement of gauges, no lights, no noises, no radio, nothing but the door locks work. After multiple attempts, BAM, she will fire like no issues. (This made me think ICM but then there is this...)

3. While driving, all of the lights on the DI will flash, and the gauges will go from 0RPM to the top, and 0MPH to the top rapidly then back down. All gauges die except the coolant temp gauge. Now, when the lights flash, the coolant temp gauge spikes forward and backward in sync with the lights flashing. During this time, you can feel the power shut off (Ignition dies). It's so quick turning off and on that you just ultimately buck like you can't drive stick.

3. The lights seem to flash when you're on the gas. Haven't noticed any flashing/cutting out at a light yet.

4. After shutting the car off, there is a noticeable click from the passenger foot well, almost like the module on the other side of the passenger fire wall could be clicking. Once the hood is popped, it's hard to hear it from outside the car. Seems to be in the dash somewhere.

I think that's it for now, will add more info as I remember/answer any questions.

Two cars breaking down and a ton of snow =

Thanks Tech.

ramairetransam

iTrader: (18)

sounds like your vats is acting up , i bought a resistor kit off ebay for 4 bucks with 15 different resistors. Look into vats disable . bothered my car late last year and took car of it .

TurboDSMJ

Thank you for the response. I believe I have an original key from '99 somewhere in my house. I will test that first in case the chip on this current key is either bad or dirty. Otherwise I will look into the resistor pack.

Or could a tuner use something like HP Tuners/Other to turn that off?

dailydriver

^^^I know that it can be disabled/'tuned out' with a GM Tech 2, or equivalent from Snap On or such.

(Not sure about HP/LS1 Edit/EFI Live/etc.)

ramairetransam

iTrader: (18)

vats can be turned off in the pcm so the car gives fuel but the bcm
cant be turned off. you need to do the resistor trick

chrysler kid

iTrader: (14)

Vats needs to be corrected with the resistor mod, turning it off with a tuner only tells the PCM not to cause the dash light. The body control module can not be turned off and that sends the ok signal to the PCM to start the car.

It sounds like you have a grounding issue though. Double check your alternator, battery, and chassis connections for corrosion, power and ground leads.

Sounds like your replacement alternator could be faulty or the power connection is not tightened properly

1 FMF

iTrader: (1)

do you mean the alarm is going off? because vats (vehicle anti theft system) is the passkey crap with the resistor in the ignition key. what vats does is check to see if the correct ignition key is used and that the ignition cylinder was not broken and forced to start the car. vats is controlled by the body control module (BCM) and if the correct ignition key resistor is used, then the BCM allows the fuel pump to run and lets the starter get power. otherwise the security light comes on the dash and when you turn the key to start to get nothing. vats will not set off the car alarm and make the headlights flash and horn beep.

once the correct ignition key resistor is used and the car is running, VATS will not cause the engine to shut off. vats is only in affect before the engine is running. your description in #2 sounds like a VATS ignition key resistor issue.

#3 part 2 sounds like you have a bad diode in the alternator, if you have a flicker of the headlights and all lights in the car, and the flicker gets faster with rpm. it's not uncommon for replacement alternators of questionable quality to go bad.

#3 part 1 sounds like you have a wiring problem, possibly a corroded battery cable or bad ground wire somewhere. if the alternator has been replaced, there's a ground strap that goes from it to the frame in front of engine bay. with car idling, grap and wiggle each battery cable and see if the condition happens. the battery cables especially if you've had corrosion and powdery **** at the battery terminals will go bad where the cable is connected to the side post terminal that screws into the battery. and if the car gets used in the winter i would inspect all the wiring and everywhere in the engine bay for a mouse nest and chewed wires.