outhouse

The two common failure points are clutch switch and ign switch

ZIE06Bernie

Yep now you are on the right track. Probably not a short more likely an intermittent open circuit (maybe contacts) in the clutch switch or start switch area as outhouse suggests.

jfreez

that sounds better than the body control module $$$
Clutch should be easy to bypass. Never messed with the start button, but I thought it was a momentary switch and the BCM dictated the crank cycle length.

ZIE06Bernie

Just added the wiring circuit which may assist you too. See diagram 69 for a bit more info further up the line.

jfreez

the wiring diagram really helps, thank you
I think I can handle testing the voltage out of the BCM and isolating the clutch switch, if that doesn't work, then I will have to look this over a little more before I get a grip on how the ECM interacts with the relay.
Just as a precaution, I may unplug and replug the BCM and the ECM just in case I have a little corrosion in the friction connectors.

ratomicZ06

I don't think you will find a "short", you are looking for a voltage drop either caused by a faulty connection, faulty switch or a weak signal from the BCM.

Test the ground applied to the Crank relay coil from the BCM, (A14, E12) make sure it is going low enough to properly pull in the relay. I also would go across the crank relay coil (A14, E12 to C3,A9) to check as well....basically where the "A", "B" and "C" triangles are on schematic "2 of 2".

Not sure how the access is going to be, but don't "stab" the wires, you'll just introduce issues down the road if moisture gets in. If I get time Sunday, I may pull mine apart to see.

(schematics as noted, are for C6 and Z06.)

Good Luck!

jfreez

i should be able to work on it Monday night, I am out of town at the moment. I will report back

butch353

just a short view. had starter problems found a bad connection in the under hood fuse block plug in took to stealership they replaced the top two parts of the block but left the burnt connection ( Ray Charles could have seen it ). so ordered a Racetronics jumper system with a better gage wire an comes off the alternator. NO problems. an with a head shave an cam to boot. JD.

stefuel

Wanna back up a little bit here. You push the "start button" and hear a click. Is that correct? If so, I would say the start button is working. Where is the click coming from? Inside the car or outside? I have not looked at the schematic yet so I don't know where the clutch switch is in the signal path but that is the next thing I would look at as it sounds as though everything from the relay down to the starter is OK. You have no coil voltage to activate the starter relay. I have a blue tooth digital multimeter that I can connect remotely and watch results on my smart phone which helps greatly when working alone. Im guessing you don't have one so a second pair of hands will help.

jfreez

The clicking is the starter solenoid , I have confirmed that.
with the cover off the relay, I can see it connecting and disconnecting about 2 times a second when trying to crank.
My next step is to check to see if the starter relay coil ground and voltages are in a good range.
After that, I will probably pull the fuse box apart and look for something there.

jfreez

good to know that you were able to see the problem, when I pull the fuse box apart, I hope its the same issue, that would be much better than the body control module.

silvrhand

Do you have headers? I would pull the starter and check the solenoid the solenoids with headers typically get baked and soon as you get it on the bench the solenoid will likely disentegrate.

ratomicZ06

Test for these:

Poor ground on ECM or BCM.

Poor connections underside of fuse panel.

Test clutch start switch for positive connection when depressing clutch, short its 2 pin connector if necessary for testing.

BCM (internal RUN/CRNK RELAY) provides B+ for CRANK RELAY through the CLUTCH SWITCH labeled "A". The ECM provides a ground path to energize the CRANK RELAY labeled "B". Either you don't have enough B+ at "A" or a poor ground at "B", or you have a voltage drop elsewhere that is not allowing full B+ or a good enough ground to hold in the CRANK RELAY.

Also, look at Page 33 of the schematic. It lists the procedure for testing.

If there is any voltage drop caused by excessive draw when starter is operative, there will not be enough voltage for crank relay to energize properly. Make sure all of the large gauge wires are clean and making good contact.

Hope that helps and someone correct me if I missed something. PM me ahead of time if you need help.

jfreez

no headers, new starter. wires look good. I have also cleaned the contacts.

jfreez

I will be working on these soon. not sure if my digital meter will be fast enough, might have to get an analog one to catch the pulses

ratomicZ06

Alot of the good meters, fluke for example, have an analog bar graph and min/max hold features. Be careful w old analog meters, they are low impedance and you can do harm to circuits, but ok for relays and such.

Im guessing youll end up finding a voltage drop that holds constant when you try to start it.

stefuel

Might be easier to check some of this with a simple test light. You need to figure out what signal is missing at the crank relay. Remove the crank relay. Figure out which two terminals are for the relays coil. If the socket is marked it will be "C13" and "A14". "C13" is + battery voltage from the BCM through the clutch safety switch. If you ground the test light and probe "C13" while someone steps on the clutch and presses the start button, the test light should come on solid. If not, the problem is on that side. "A14" is the ground signal from the ECM. Clip your test light to the bat+ on the alternator. Now any time the probe touches ground the light will come on. Probe "A14" on the socket and have someone try to start the car again. The light should come on solid. This simple test should get you looking in the right direction for the problem. If this car was right in front of me I'll bet I could get to the bottom of the issue in under a hour

jfreez

Thanks for the info, this saves me figuring out the socket numbers.
I should have someone over early next week so that I can run the tester while they try and start.

stefuel

Get creative and hook up the test light by any means so you can see it from inside the car so you can do it your self. I'm not a big fan of waiting for people to come and help. Push the damn button and look for the light......or not

jfreez

RatomicZ06 had the answer, bad ground.

I thought I had checked all the grounds (I checked all I could find)
Apparently the body control module picks up a ground from the back of the engine on the passenger side.
I had cleaned all the ones on the inside of the car, and all the power the connections with no luck. I finally broke down and took it to the dealer. He had a diagram that pointed to the one on the block. He had it fixed that day and only charged me the assessment fee.
As a rule I hate taking my cars to dealerships, but I have to admit, this guy knew what he was doing and treated me right, Way to go Smith Chevy....