I have a 1995 base coupe, Vin P as they say.

I have recently been having trouble with the VATS system not sending the fuel enable signal. You can tell, because: car cranks, gets spark, but no fuel. If you hold the throttle open, you can sometimes coax a backfire from the residual fumes.

The problem is this: when I go to the red PCM connector to check for a signal, there is no wire connected to pin 25, which should be circuit 229.
Connector locations 24-30 are empty. All other locations match the factory pin out diagram.

I have owned the car since 1998 and it is very unlikely that the vats system has ever been tampered with.

Has anyone encountered this ? I had intended to install a vats bypass chip to the fuel enable circuit to solve my intermittent problem. But I don't know where to look.

Thanks, in advance for your help.

 

Have you verified you have fuel pressure?
Have you verified with a noid light if the injectors are being pulsed?
On starting if you hold the throttle open past 3/4 throttle the PCM will operate in clear flood mode and not pulse the injectors.

The 95 Corvette did not use that pin. Other vehicles like the Camaro and Firebird did use that pin for the Fuel Enable Disable signal but they did not have a CCM like the Corvette in 95.

I've never heard of anyone injecting a square wave signal into that pin to bypass a no pulsing of the fuel injector for a 95 Corvette. It would be interesting to see if that would work.

The CCM does a password exchange with the PCM when you turn the ignition On.

You can verify the status of the FED signal by doing the following.

Connect pin 4 or 5 both ground to pin 12 on the Diagnostic connector located above the drivers right knee. Turn the ignition On. The Speedometer LCD will display any trouble codes for the different
modules.

Module 1 CCM
Module 4 PCM
Module 9 ABS/TCS
Module A air bag

You will see 1.0 after the display stops.
Press the Trip/Odo button until you see 1.3
Press the Eng/Met button once. You should see 01
to the right of 01 you should see either a 0 or 1
A zero indicates pulsing of the injectors is disabled.
A one indicates pulsing of the injectors is enabled.

 

Thanks, very much for the quick education! So, I went through the code retrieval and got a 0 for the pulsing.

However, I noticed that when the doors unlocked as I approached with the remote, the interior lights on the door panels did not come on. So, I used the key to lock and unlock the driver's door and the lights came on and the car started right up. I suspect that the worn door lock had stayed slightly askew the last time I removed the key. I'm going to have a look at the connections and accessible contacts in the lock. I'm hoping this proves to be the source of my problem. Vats had not given me any problems in 17 years. But a couple of strandings can be pretty frustrating!

Thanks again!!

 

The PKE does send a negative pulse to pin D15 to disarm the alarm.
Either door key does the same when you turn the door key to unlock.

To test the door key cylinder unlock switch which is mounted on the back of the door key cylinder.

Do the same CCM diag. as you did. When 1.0 appears press
Trip/ODO until 1.3

Press Ent/Met until you see parameter 03
Should see a 0 in the far right digit.
Turn either driver side or passenger side door key to the Unlock
position.

Should see a 1 for the far right digit.

Turn key back to remove key. You should see a zero in the far right digit.

Some of the Parameters

O1 FED signal 1 enable 0 disable
02 English Metric switch 1=Metric the switch position not updated while in diagnostic mode.
03 Door key switch. 1 indicates key is in the unlock position
04 Right door ajar 1 door open
05 Left door ajar 1 door is open

 

so does it have to be disabled or enable

 

I doubt the OP will respond, he has not been active on the forum for over seven years. Thread closed