-

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I can clear the code but turning the ignition key gives me engine cranking and sounding like it will start but it won't start

Also the DIC usually displays the Corvette logo and more Now it does not display anything or sometimes only Corvette and then goes blank, Can not read codes by pressing Options and then Fuel 4 times. Did get a Reduced Engine Power one time but nothing now. Battery is a Duracell 78 and is only 6 months old. Used a charger to get it fully charged but still won't start. Have the Service Manuals and traced out continuity of wires going to TAC, Throttle Body Position sensor and Throttle Body Motor. Had someone depress accelerator pedal and saw resistances change on the wires to the accelerator pedal. Have a replacement TAC coming and will see if plugging it in solves the problem. Did replace ignition switch several years ago because the sensor to read the key pellet resistance was bad. When replacing the switch also added resistors and a switch to bypass the key resistance with resistors of the same value as the key pellet. The switch is a single pole double throw with center off and does not appear to be involved in this problem.

I was looking for the posts that described taking the ignition switch apart and cleaning or burnishing the contacts but can not find that post. My original ignition switch was OK electrically except for the two contacts in the front of the switch to read the key pellet resistance. If necessary could pull the connector off the switch in the car and test it out with the original switch . For some reason the original switch does not NOW turn with the key which came with the car. Can't remember how to remove just the locking mechanism and just have the plastic rear of the switch to try and see if it will start the car.

This thing is mind boggling
Anyone got any ideas on what it the root cause and what to do to fix this?

 

 

I dug out the original ignition switch that I replaced which had bad contacts for the ignition key pellet but was otherwise not giving me any codes or problems. Couldn't get the lock cylinder out but drilled it enough so I can use a screwdriver to turn to the various key positions. I have already bypassed the theft deterrent contacts with the proper value resistors, Don't remember if I can access the white and black plugs without tearing up the dash but I want to plug the old ignition switch in with the TAC module that came with the car and see what happens.

You suggested G106. Exactly where is that, on the fender wells or elsewhere?

 

 

with the c5 being so finicky to voltage i've learned the first thing to do is have the battery tested.just because it's fairly new doesn't always mean it's good.
second is check grounds and clean them.
third is check/replace ignition switch. i've seen the switch be the cause of a lot of random issues with throwing codes

if all three of these things are for sure good,then it starts to get more complicated finding the problem.

 

Took battery to Advance Auto and had it tested. 12.6 Volts and showed up as GOOD. Replaced TAC with one from a 2002 C5 (mine is a 1998) with a different PN, but this PN is listed on the interchange list posted on several sites on the internet. Supposedly all TACs from 1997 thru 2004 are interchangable, same results, cranks like crazy but no start. Will try replacing Ignition switch with one I removed from the car several years ago since the contacts on the lock cylinder were shot and could not read the ignition key pellet. The rear part of the switch which actually supplies current to multiple systems and the starter was OK. Now the cylinder is stuck in the rear part of that switch. Can turn the cylinder after drilling out the center of the lock cylinder but can't remove it. Discussed at length in another thread. Have to spend several hours dissecting the dash, console, etc. to get to the ignition switch in the car. Will update as I get there.

UPDATE: Removed the lock cylinder from the EXTRA Ignition Switch by putting a screwdriver in the smaller hole in the switch while it is on the ON position. Now have to go back and take the car apart to get to the current Ignition Switch but have been sidetracked by other pressing matters. Will update when I get the car apart.

 

See Update above

 

Finally ripped the dash apart and got the Ignition Switch out. Have the switch I had in the car for about 10 years but I located a new unused switch and started with that one. Took lock cylinder out and inserted it into the new plastic electrical rear part of the switch which has all the electrical components except for the key pellet sensor.
Plugged in a OBD code reader and turned on the Ignition using the new switch. Had the P1518 code stored. Erased the code and did not see it return.
Turned the key to start. Engine cranked just as before but this time the car started. Left it run for a half hour as the car had not been able to start for quite a while.
As it was getting dark I decided to close up the car and work on it tomorrow. Am surprised that the Ignition Switch gave the TAC code and nothing else.
You can't always believe the troubleshooting steps to fix the real problem. I know this would be a multi-hundred dollar FIX if I had to go to a stealership. Sometimes going in a different direction than the one outlined in the service manual is the way to go.