So I've posted this on other sites but haven't found anything that helps. So here's the story i bought my dads 96 SS all original only thing is it hasn't been driven in 3 years. So I emptied the fuel tank and put in 5 gallons of fresh fuel and half a can of seafoam. Changed the fuel filter and oil. And it still wouldn't start. After checking the forums found that it was the TDR relay and bypassed it by jumping the purple to yellow wire. Now it starts and runs for 10-20sec and dies like the key gets turned off. I've since then tried by passing the VATS with a resistor but it didn't change a thing i cut the two white wires and put the resistor in and it does the same thing. I also have a cheap scan tool and it doesn't show any codes. I had the ICM tested like 16 times and it passed every time. Hooked up fuel pressure gauge seems to stay around 41 psi. Hooked up a timing light and it sparks as it dies. Hooked up a NOID light and that seems to shut off right before it dies so I'm guessing that is what kills it. I also checked idintifix and they some people had success replacing the ecu I ordered one off ebay with the same numbers and it still does the same thing. Please someone HELP!!!
96 LT1 Starts then DIES!!! Please Help
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Sounds like a vats problem to me. While the resistor trick works on about 95% of vats problems, it would seem you fall into the 5% category where it doesn't.
So before we go to the next step, let's make sure you measured the resistance of your old key correctly and put the correct resistor value in. shbox.com has a good write up on vats and a chart there which lists the 15 correct resistance ranges that GM used in these cars. Does your resistor value match one of the 15 on the chart. If no, correct resistors to the right value. If yes, lets move on
One final note, bypassing the starter relay by putting the large yellow and purple wire together is not the best way to get starter to work. This is why. By doing that you have disabled the safety system designed in that won't let car start in gear. With automatic trans in your car, it will no start with gear selector in any position, or if manual, without the clutch pedal being pushed down.
A better way to bypass the starter relay is to cut the small wire on the relay, it's the only small wire there. It's yellow/black on earlier models, not sure about 96, however. Splice in a piece of wire a run it to a good ground. Now, if relay and wiring are good, starter will crank engine, and safety interlock will be in place.
Next you need to go to Baker Electronix - GM VATS Bypass there you will find the 50 hertz vats bypass module. What this module does is send the 50 hertz fuel enable signal to the pcm, so pcm will open the fuel injectors. When you hook it up, you provide it with power, ground, then cut the wire that goes from bcm to pcm and splice the module wire into the original wire going to pcm.
Now every time you turn ignition key on, pcm will be getting fuel enable signal so pcm will open the injectors.
So before we go to the next step, let's make sure you measured the resistance of your old key correctly and put the correct resistor value in. shbox.com has a good write up on vats and a chart there which lists the 15 correct resistance ranges that GM used in these cars. Does your resistor value match one of the 15 on the chart. If no, correct resistors to the right value. If yes, lets move on
One final note, bypassing the starter relay by putting the large yellow and purple wire together is not the best way to get starter to work. This is why. By doing that you have disabled the safety system designed in that won't let car start in gear. With automatic trans in your car, it will no start with gear selector in any position, or if manual, without the clutch pedal being pushed down.
A better way to bypass the starter relay is to cut the small wire on the relay, it's the only small wire there. It's yellow/black on earlier models, not sure about 96, however. Splice in a piece of wire a run it to a good ground. Now, if relay and wiring are good, starter will crank engine, and safety interlock will be in place.
Next you need to go to Baker Electronix - GM VATS Bypass there you will find the 50 hertz vats bypass module. What this module does is send the 50 hertz fuel enable signal to the pcm, so pcm will open the fuel injectors. When you hook it up, you provide it with power, ground, then cut the wire that goes from bcm to pcm and splice the module wire into the original wire going to pcm.
Now every time you turn ignition key on, pcm will be getting fuel enable signal so pcm will open the injectors.
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Why not put the TDR relay setup back to original and start over? That way you know for sure you have the VATs key bypass working or not more easily (will or won't crank) instead of guessing about the fuel cutoff reason. Everything cocobolo95 typed is true, but you should only need to use the 50Hz generator device if you either don't have a BCM (engine swap) or yours is defective.
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