My 95 corvette sometimes won't crank and then come back a little later then cranks with no problem. This has only happened three times in the last three months. Usually drive the car three times a week.

 

When you turn the key to the ON position and it does not crank, look at the security light (on left) and see if it is on steady. If it is, then you have a VATS event and you should clean the key pellet and contacts in the key cylinder with a Q-tip and alcohol.

If the security light is not on and it's not cranking, then you need to start to look at the electrical start circuit for the starter and even the starter. If it is electrical, a common cause is the solenoid on the starter and a tap on it may get it going and validate the problem. If it not the starter, then a look at the switches, interlocks and connections is required.

 

Good information, thanks for the tips

 

Check the negative ground connections at the starter. If there is corrosion or a loose ground wire this can cause an intermittent problem. Also check the connections at the positive and negative terminals at the battery. They should both be CLEAN and TIGHT. Report your findings back here

 

Checked on those items and all was ok .....notced battery volts
was only 11.7v so charged it up and started ok ....
now courtsey lights won't go out when key off and door closed
after waiting ....had to pull out fuses ....any ideas ?

 

The POSITIVE battery cable attaches to the starter solenoid. The starter is grounded through the metal body of the starter to the block.

The negative battery cable attaches to the side of the block above the oil filter.

 

Battery tested, after load went down to 11.7 volts.
Purchased new Napa battery. Thanks for info.

 

Ozzstar,
Found this thread and trying to get some advice. Problem similar to the poster.
I've got a 95 LT1. Parked in garage last week with no problem and now have problem. Insert ignition key. Car lights up, fuel pump kicks on. No crank. Battery replaced and fully charged. Tried spare key. Same problem. Security light not solid or flashing. From what I've read that pretty well eliminates VATS. Also tried both keys with car in neutral hoping to eliminate that safety switch. Have power from battery to starter. Ground connection appears to be good. Have replaced starter relay but to no avail. Is there another solenoid somewhere I'm not finding?
Thanks for your help.

 

Sounds like a bad starter.

 

Do you get a "click" from the starter or NOTHING at all?

Very likely if starter is OE the contacts in the starter are wasted. Contacts and plunger should be available locally. Generally less than $25 will buy parts and is more preferred than an off the shelf reman from an AP store.

This link will take you to contacts/plungers for 'denso starter so you could get an idea of what you're looking for at a "local" vendor.

http://www.nationsautoelectric.com/densoparts.html

 

Nothing at all. Orange LCD screen in center of cluster also stays illuminated when I remove the key. Even more curious, test light shows I have no power in fuses 11, 12, 13 yet interior lights on with doors closed. Dimmer switch off. Do I have a gremlin or am I over thinking it? Today I will jack up the car and pull starter.

 

1) If you are saying the dash cluster LCD back light is on even with the key off.
2) The interior courtesy lights are staying On with the doors closed.
3) The starter doesn't engage with the key in the start position.

They all point to a problem with the Central Control Module. (CCM).
The CCM controls the Courtesy lamp relay.
The CCM controls the bulbs that back light the LCD.
The CCM controls the Starter Enable Relay by grounding the control side of the relay,

Fuse 11, 12, 13 provide power for the incandescent courtesy bulbs when the headlight switch is in park or head. These are not the same courtesy lights that light when the doors are open.

Three fuses power the CCM.
Verify the following fuses have 12 volts to them.
Fuse #35 CCM1 Hot in Run or Start
Fuse #39 CCM2 Hot all the time
Fuse #16 CCM3 Hot in Run

Verify ground G106 is clean. It's located around the oil filter housing bolted to the engine block. The negative battery cable also connects to the engine block at G106.

If all those check out you can do the following to verify the problem is the CCM.

You said you know where the starter enable relay is.

The Relay has 4 wires going to the relay socket.
Heavy gauge Yellow wire which is 12 volts from the ignition switch.
Heavy gauge Purple wire which goes to the starter solenoid.

Remove the relay from its socket.
Jump the heavy gauge Yellow wire to the heavy gauge Purple wire.
Turn the ignition to start and the starter should engage.

If that works. To further verify the problem is the CCM.
Reinstall the Starter Enable relay.
Back probe the small Yellow/Black wire.
Turn the ignition key to Start and hold it in the Start position.
If you read around 12 volts on the Yellow/Black wire that indicates the CCM is not grounding the Yellow/Black wire which it should if the Security light is not on solid on the dash cluster.

 

Hooked on Vettes,

Huge help. I ran through all of your diagnostic recommendations. Thanks for making it step by step. I did get the starter to engage when I jumped the yellow and purple wires connected to the relay. I do have 12v on the yellow/black wire when I turn and hold the ignition key in the start position. The security light is not flashing or solid.

So I suppose I have a CCM problem. Now what? Can I permanently jump the purple and yellow relay wires or am I faced with a CCM replacement? Suggestions?

 

Also, there is a heavy gauge purple wire that goes into a relay on the right underside of the steering wheel. That purple wire is a bit melted and corroded where it meets the connector. I have replaced that relay just in case. What does that purple wire do and might it have anything to do with my problem?

 

Can a battery go dead even if it is connected to a battery tender? My 1990 is dead even though I always hook it up. I went to drive the Vette yesterday and the interior lights went on but when I turned the key, everything went dark. No cranking, no interior lights. How can this be?

 

That proves the CCM is not grounding the Yellow/Black wire and it's not because the key pellet resistance is incorrect. (Points to the CCM).

You can disable the interior courtesy lights by removing the Courtesy lamp relay located under the front edge of the dash on the passenger side. May have a black plastic cover covering the relays. You can still control the courtesy lights manually by using the headlight dimmer switch.

There are 4 relays under there.
The Courtesy lamp relay will have 4 wires going to the relay socket.
Black wire, White wire, Orange wire and a Gray/Black wire.

There really isn't anything you can do to disable the lighting of the LCD with the key off unless you put a switch in series with the wire that provides 12 volts to the bulbs. That would be a Bubba Fix.

rockauto.com lists a re-manufactured Body Control module (BCM) also called a Central Control module (CCM) for $111.00 plus $60 core charge. They usually have a 5% discount code coupon if you do a google search.

They show two CCM's so you would need to remove your original CCM and verify the part number. I believe yours should be GM #16223622

A Re-manufactured unit will learn your new key pellet resistance but you need to program the replacement CCM using a Tech 1. I've never programmed one but it does allow you to set the mileage and I believe what options the car has like C68 auto climate control. You have up to 100 miles to program the mileage. After that the program is disabled.

The Defogger relay located on the passenger side of the steering column has a Purple wire, Red wire, White wire and a Brown wire.
If that is the Purple wire you are asking about, it is the 12 volts that goes to the rear defogger grid.

I do have a Tech 1 you can borrow. Just pay for the shipping if you need to use it.

Here is a picture of the relays under the dash.

 

Batterys don't last forever.

 

Yes batteries do go bad.

Remove the battery. Charge the battery using the battery tender.
Then take the battery to an auto part store and have them load test it.
If they say the battery test good you need to measure the current draw when
the ignition is off and no interior courtesy or under the hood lamps are on.

Should be less than 30 milliamps. If the current draw is more than that, something
is drawing current when it shouldn't be and that is causing the battery to discharge.

 

I'd suggest you load test the battery. It may not be taking the charge.

 

For what it's worth, my 1996 GMC K2500 Suburban had this issue. It had the problem with the original engine and also with the new engine I put in it. I did the usual...threw money at it in hopes of fixing the problem because the fixes I knew of weren't working.

Anyhow there was a sensor up beside the upper radiator hose gooseneck on the engine that was damaged. That same sensor went on the new engine for compatibility sake. I bumped that sensor one day and the top came off. I replaced it and never had another problem.

Just giving you another avenue to explore.