twistedsymphony

I've got a 1999 Corvette LS1 that I'm swapping into a 1995 Nissan 240sx.
Vette motor was originally mounted to an automatic but I'm using a T-56 out of a 2001 Camaro SS.

I finally got everything finished.... went for the inaugural first start but I've got nothing, it cranks strong but wont fire, not even sputter.

Things I've already checked
-everything, including the Crank angle sensor is plugged in, only thing not plugged in are Rear O2 sensors, since I don't have them.
-The fuel pump turns on and primes,
-I'm getting power at the Coils
-I'm getting power at the injectors
-I'm getting power at the MAF, TPS, PCM (battery and ignition), etc.
-throttle opens and closes like it should. (stock Drive-by wire setup from the corvette)
-no leaks anywhere.
-OBDII port has had the wiring triple checked.

I tried to hook up OBDII and I got an connection error "no response from computer" the scanner said that it found the BUS network but the computer wont respond.

I plugged the scanner into my friends WRX and it read his car fine so I know the scanner is good.


I'm assuming that if VATS is the problem then I should still be able to connect via OBDII right? Failing that the only thing I can think of is a bad PCM... anyone have any other ideas? or other things I might be missing?

the PCM has to be working in some capacity though because it is illuminating the check engine light, and it's turning on and off fuel pump like it should.

aknovaman

iTrader: (7)

Ensure you have 12V at pin 16 of the OBD2 port and have 12V at the PCM blue connector pins 19 and 20 with the key on. You should have PCM data then.

twistedsymphony

I've checked all that

OBDII pin 2 is connected to blue pin 58

OBDII pin 4 and 5 are ground

OBDII pin 16 has +12V from the battery

Blue 19 - has +12V switched on with the ignition
Blue 20 - has +12V from the battery
Blue 57 - has +12V from the battery
Blue 58 - goes to pin 2 on the OBDII port

is there something else that could be hooked up wrong that would prevent OBDII from functioning properly?

Bad Chad

iTrader: (94)

Have you had the Vats turned off in the computer? If not that’s why it won't start, I was dealing with the same issue this weekend.

Check your grounds, if you do not have a good ground it will not recognize the +

twistedsymphony

grounds are good...

I don't know if VATS is off or not, (I was told it was when I bought the motorset) but without the ability to connect via OBDII there's no way to turn it off or even check the status.

Will VATS block OBDII as well? I thought it just threw a code.

I was considering building a Bench-harness for reprogramming but I can't for the life of me find where I can buy just a PCM connector...

twistedsymphony

a mechanic friend of mine stopped by, his OBDII scanner had no problem connecting, only code was EVAP.. so my USB scanner doesn't work with LS1s apparently.

we tested fuel pressure at the rail and got 0psi... swapped the fittings on the FPR and it fired right up

robbyredneck

iTrader: (1)

HAH. i didnt know there was a possibility for swaps to work on the first try. good deal and thanks for the update.

Bad Chad

iTrader: (94)

Good to hear you got it...

twistedsymphony

Don't pop the Campaign just yet.... :?

a few seconds after it starts the engine dies..... I assumed it was VATS

I have the full Factory Service Manual so I've been pouring over the diagrams and pinouts and can't find a single reference to VATS in all of the Corvette information.

It seems to me that the BCM in the corvette simply triggers a relay that disables the starter motor.... no VATS, the pin out of the Vette PCM is nearly identical to the Camaro from that year... except the Vette PCM doesn't have a pin for VATS, I even checked my connector (Red #30) and the hole is plugged... it never had a wire going there.


The only code my PCM is throwing is for the EVAP sensor "out of range" which is apparent since it's not hooked up.

So anyone have any idea why pretty much as soon as my car starts it dies again?

The only thing I could come up with was bad gas, it only had about a gallon or two in the tank so I threw a little dry gas in there and added 6 gallons of fresh premium... it didn't make a difference.


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Someone correct me if I'm wrong but if VATS is killing the engine it will throw a code for that correct?

If it's not VATS what else could it be?

Bad Chad

iTrader: (94)

If it is just starting and dying then the Vats needs to be turned off. When it dies does it ast like it is running out of gas?

I was dealing with this till my brother came over with HPTuners and turned them off. After that the car ran great.

twistedsymphony

does a C5 Corvette have VATS? because I have a VATS emulation module... but nowhere to hook it up.

cutlass_455

iTrader: (2)

VATS will allow the car to start and then die. You have to use a program like HP Tuners or EFI Live to delete it. Or get a bypass module, Ive never had any experience with them, I just used HPT on my conversion. I think these modules talk to the BCM and the BCM tells the ECM all is good and to keep running. So if you dont have the BCM you might be screwed. Can you hook HPT up to it instead??

twistedsymphony

after a bit more research I found that the C5 does have VATS but it works differently than other cars...

there is no VATS pin on the PCM that you can hook a bypass module too. instead the BCM has a password that it sends to the PCM over the OBDII serial wire.

in any case I sent my PCM out to get reflashed with VATS disabled.

Broncoviejo

Hello guys,

I have a stock 2000 tahoe with a 5.3 motor but, sometimes it doesn't want to start. Check the fuel pressure at the fuel rail and its at 50 psi. Any suggestions?