Car won't start - suspect PassKey/VATS?? - Chevy Impala SS Forum
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post #1 of 33 (permalink) Old 05-28-2017, 10:25 AM Thread Starter
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Car won't start - suspect PassKey/VATS??

My 95SS has the Z28 cluster mod, so no Passkey/Vats warning light. I went to get gas last night and car wouldn't start back up. Towed it home and did the following checks:

1. plenty of battery and good charge.
2. when starter switch is turned on, you can hear the fuel pump whine nicely, but no starter at all.
3. no voltage at the yellow starter switch wire, at the starter, when turning key to start.
4. since my car is a 6 speed, my yellow switch wire, coming off ignition switch, is spliced, for the clutch switch. So coming off the ignition switch, when key turned to start, i see voltage.

Might my problem be the Passkey/VATs system? From the wiring diagram, the yellow wire from the ignition switch goes to the module. I suppose i could make sure I dont' have a break in my starter switch wire, somewhere under the engine bay.

One other question - the wiring diagram suggests (for the (9C1 police) you can simply run the yellow wire from the ignition switch directly to the starter and completely bypass the VATs. Has anyone done this?

'95 DGM Impala SS, 383, LT4 cnc heads, LT4 matched intake, Holley 58 mm t/body, GM 846 cam, GMPP 1.5 rr's, F-body MAF, BH OBD I PCM, LT4 knock module, K&N cold air, Edelbrock headers, Flowmaster exhaust, BBHP #73 6-speed, 4:10 gear, sloted and drilled rotors, Z28 cluster.

'96 Buick Roadmaster Limited Wagon, mostly stock.

74 Ford F100, 390 HP pulled out of a 67 Fairlane GT

91 Mustang LX notchback, 5.0L, 63,000 miles, pristine.
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post #2 of 33 (permalink) Old 05-28-2017, 11:12 AM
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Take all necessary safety precautions. (brakes on, in neutral, and others)

Turn key to run. Run a wire from the starter battery cable to the yellow wire stud this will crank the engine.

If the car starts and runs you have a issue with the starter circuit. If it just cranks you have a VATS problem. The light would tell you that it may not be sending the PWM to the PCM.

The Four VATS Modes:

VATS sees a correct resistor value, powers the VATS/starter relay to allow cranking, and sends a PWM signal to the PCM.

VATS sees a open circuit, lights the VATS light, powers the VATS/starter relay to allow cranking, and sends a PWM signal to the PCM.

VATS sees a bad resistor value, does NOT power the VATS/starter relay to allow cranking, and does NOT send a PWM signal to the PCM.

The engine is running and the resistor signal becomes bad. The engine will run and the VATS light will be turned on.


The other quick test is to unplug the key cylinder from the VATS. The VATS should let you run the engine then.


Quote:
One other question - the wiring diagram suggests (for the (9C1 police) you can simply run the yellow wire from the ignition switch directly to the starter and completely bypass the VATs. Has anyone done this?
The 9C1 still has a VATS. The key resistor value is a wire loop.(dead short) The VATS still sends the PWM to the PCM. Yes the starter relay is missing.

When the VATS is programed out of the PCM this is part of the mod. Some people also just power the relay from the VATS wire harness.

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post #3 of 33 (permalink) Old 05-28-2017, 11:38 AM Thread Starter
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Yellow stud?
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post #4 of 33 (permalink) Old 05-28-2017, 12:00 PM
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Quote:
3. no voltage at the yellow starter switch wire, at the starter, when turning key to start.
Use a big wire to connect the battery starter wire to the starter solenoid connector on the starter which has the yellow starter wire normally attached. (on most cars a stud and nut) This will crank the engine.

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post #5 of 33 (permalink) Old 05-29-2017, 08:57 PM Thread Starter
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Red face

Quote:
Originally Posted by Z09B4U View Post
Use a big wire to connect the battery starter wire to the starter solenoid connector on the starter which has the yellow starter wire normally attached. (on most cars a stud and nut) This will crank the engine.
Thanks man. Just making sure I do it right - you mean i should leave the yellow wire attached at the starter or disconnect it? and basically just 'jumper' the two connections at the starter (heavy wire from the B+ connector to the switch connector)? Or should i run a separate leg from the positive terminal to the switch connector? or does it matter?

One more question - does $eeHack have a VATS select/ECM switch capability? I know it has some controls but limited writing.

Thanks-

'95 DGM Impala SS, 383, LT4 cnc heads, LT4 matched intake, Holley 58 mm t/body, GM 846 cam, GMPP 1.5 rr's, F-body MAF, BH OBD I PCM, LT4 knock module, K&N cold air, Edelbrock headers, Flowmaster exhaust, BBHP #73 6-speed, 4:10 gear, sloted and drilled rotors, Z28 cluster.

'96 Buick Roadmaster Limited Wagon, mostly stock.

74 Ford F100, 390 HP pulled out of a 67 Fairlane GT

91 Mustang LX notchback, 5.0L, 63,000 miles, pristine.
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post #6 of 33 (permalink) Old 05-30-2017, 12:48 AM
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Quote:
One more question - does $eeHack have a VATS select/ECM switch capability? I know it has some controls but limited writing.
I have not tried $EEHack. It sounds great but he explains that he adds code to the PCM and stores extra information as well. Since I am not sure that Tunner Cat will erase or write over the extras I will only try it on a spare PCM.

Quote:
should leave the yellow wire attached at the starter or disconnect it? and basically just 'jumper' the two connections at the starter (heavy wire from the B+ connector to the switch connector)
Yes leave the yellow wire attached at the starter.Yes just 'jumper' the two connections. Please read the ramblings below for extra information.

When I was checking in the injector information I found a easy way if you have a scan tool. The VATS fault will not turn on the MIL light But it will set DCT 46 (OBDI 46) If you find this you will have to work your way through the VATS circuit.

The other quick test is to unplug the key cylinder from the VATS. The VATS should let you start and run the engine then.

If you can not scan it what I am suggesting is a $0.10 bump switch.

In the good old days when things were simple we needed to rotate the engine to adjust valves, find top dead center, ect.

We would go to Sears or K-Mart (or Snap-On) and get a pre-made switch with wires with electrical clips on the wires. Clip one to the battery and the other to the starter solenoid. Push the button and the engine would crank. If the ignition switch was on run the engine would start.

The $0.10 version is a 4 inch piece of 12 ga wire. Gloves and glasses for safety. Prep the car for starting, then set the ignition to run, Press one copper wire end on the starter's battery stud. Get ready for cranking and press the other copper end to the solenoid's stud on the starter. (sparks will fly do not worry) Hold the wire firm. Remove wire when the engine starts.(or not) Touching the wire to anything else will heat the wire and may start a fire.

You do not have to remove any wires from the starter.

In the bad old days before column locks and computers thieves would clip a wire to the battery and clip the other end to the spark coil. Under the car they would jam a wrench on the two starter studs. The engine starts and the car disappears.

If you do not think this is safe ask some one who works on old cars for a starter/bump switch. They were also part of a kit that would have a dwell/tac meter, and a timing light.

The idea is to totally bypass the starter circuit. The wire is your very crude starter switch.

Touch the wire, engine starts, and you know that the VATS is sending the PWM signal to the PCM which allows the PCM to run the fuel injectors. No VATS signal it may start but it will stall.(no fuel injection after cranking)

If it starts you will still have to sort out what is not passing the start signal. In your case you can start at the column switch, check the clutch switch, and (hardest) check at the VATS/starter relay.

Click on this:

Goldsswagon

Look at starting circuit and pass-key diagrams on Goldsswagon's site.

Z09B4U

Last edited by Z09B4U; 05-30-2017 at 12:52 AM.
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post #7 of 33 (permalink) Old 05-30-2017, 08:16 PM Thread Starter
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Just got back in town and jumpered the battery B+ over to the switch, with the key in RUN. Starts right up and runs fine. Looking at the wiring diagram, the yellow wire (circuit 575) coming from the theft deterrent relay might be bad, from connection A2 ? It seems as though the Fuel Enable Output is fine, but the starter enable output is not. The clutch switch is fine and the column switch is also fine (i get 14V when turning key to start, at the yellow wire coming from ignition switch.

I am now thinking the theft deterrent relay, as the fuel enable circuit doesn't go thru this, but only the starter enable circuit.

thanks-

'95 DGM Impala SS, 383, LT4 cnc heads, LT4 matched intake, Holley 58 mm t/body, GM 846 cam, GMPP 1.5 rr's, F-body MAF, BH OBD I PCM, LT4 knock module, K&N cold air, Edelbrock headers, Flowmaster exhaust, BBHP #73 6-speed, 4:10 gear, sloted and drilled rotors, Z28 cluster.

'96 Buick Roadmaster Limited Wagon, mostly stock.

74 Ford F100, 390 HP pulled out of a 67 Fairlane GT

91 Mustang LX notchback, 5.0L, 63,000 miles, pristine.

Last edited by Alchemist; 05-30-2017 at 08:44 PM.
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post #8 of 33 (permalink) Old 05-31-2017, 12:13 AM
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If I ever take the dash off I think I will replace that relay.

The good thing is we diagnosed the VATS with a piece of scrap wire. We could have used a code reader voltmeter, or a oscilloscope. These systems are not hard to fix at home if you sort out the logic.

I would have bet on the clutch switch. I always use the clutch switch to power a relay. I do not think they like the high current of the starter circuit.

The clutch switch would have been the second place I would have tried a jumper wire.

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post #9 of 33 (permalink) Old 05-31-2017, 06:05 AM Thread Starter
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So why not just run a new yellow wire from the clutch switch down to the starter switch, at the starter, bypassing that relay?
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post #10 of 33 (permalink) Old 05-31-2017, 06:06 AM Thread Starter
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The relay is too damn hard to get to!
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