m0nk

I have had a problem with my car for the last few months, I tried solving it myself, but was not able to. I am now working on the car with a local GM mechanic and after 2 days we are still stumped. It is a no crank no start. If ground the Theft Deturrant Relay(TDR) the engine cranks, but still does not start. The TDR has all proper powers and grounds while key is in the "run" position, but when switched to "start", the ground is pulled from the TDR disabling the ignition and cranking. As stated if i ground the TDR the engine cranks, but I recieve no spark and no fuel. I have fuel pressure, but the injectors are not firing.
We both had a strong feeling it was the BCM, but we replaced that and still the same problem occurs. I am getting no trouble codes, nor a security light. The resistance of both of my keys are exactly the same, and both fit well within the values listed, additionaly the resistance at the BCM is also well within the allowed "chip" values.
The PCM is also functional, as it is fresh from madz28.com, my old one did not go bad, I just needed a new tune and had a old fried pcm so I had it socketed and put it in the car to rule out a bad PCM
We both have a strong feeling that this could be a wiring problem, such as a bad ground or a power wire that went bad over time, but have not found it yet. If anyone has any ideas or has had something simiar occur please post here with ideas, options, or suggestions.

Robs97Z28

sound like your ignition switch is bad. from what i have read on here, it seems to commend problem on same of these cars. visit shoebax's web site, tons of good info there.

shoebox

Your GM mechanic should be proving if the ground for the TDR is coming out of the BCM or not. If it is, and not getting to the TDR, then you have a wiring problem between them.

roguedriver

Do you have an aftermarket alarm in there with an anti-theft option (ignition kill)? If you do, don't rule that out....

Ken R.

m0nk

Robs:The BCM is getting power from the Ignition switch from the 2 wires that should be supplying the bcm from the ignition switch, also I have changed the igntion switch just to rule out that.

Shoebox: The BCM is supplying the TDR with the proper ground when the ignition switch is in the "run" position, but as soon as I switch it to stop the TDR no loger recieves the ground, I will check to see if the BCM still puts out the ground later today when I get a chance, It could cutting out between the 2 when I switch it to start.

roguedriver: I do not have an aftermarket alarm, just the stock alarm, and am recieveing not securty light, but the light still flashes a light check when I turn they key so i know its not just a burnt out light, I'm really not getting a securty fault.

shoebox

I would expect the TDR to release when not in RUN or START.

Did you put in a new BCM or a used one?

m0nk

Sorry I mystyped, the TDR only clicks on when I switch the car to "run". But when I switch the car to "start" it desconnects the ground.

The BCM was brand new from GM

m0nk

Shoebox: http://shbox.com/1/g103.jpg that ground for the PCM, if that were to be disconnected, would the PCM still show a tps voltage when depressing the gas? I ask because that ground runs past my headers and could be burnt through, but I somewhat discount this because when we connect to the PCM with his TECHII, We get readings on things such as the tps voltage.

m0nk

Didnt get to check it yesterday due to the rain, but today I confirmed that as soon as I turn they key to "start" the BCM stops supplying a ground to the TDR.

slopokrodrigez

Since the ground seems to "go away" when the key is in the start position only, it does not seem as though it's wiring. Did the problem show up after the new BCM was installed? When the BCM was replaced, was the proper procedure followed to recognize the key pellet at power on? Have you tried the resistor trick in the sensing contacts wiring like we do to bypass the system?

m0nk

The BCM was replaced hopeing to solve the problem, as we thought it was just a faulty BCM not giving the correct ground. We feel that the resistor trick is not needed because the measured resistance of the key is the same as the measured resistance on the two wires leading to the BCM. Again I do not think this is a passkey issue beacause I am not getting a securty light.

slopokrodrigez

I couldn't agree more about the security light. BUT who knows what happens if the BCM is not set properly at first power on. I guess if the BCM wasn't set properly, even if you do the resistor bypass, it still won't work anyway.

Here's what the GM SM says for engine does not crank, security light not on:

check for battery voltage at BCM connector C3, pin D5.

KOEO, now check BCM connector C2 pin D for battery voltage.

Check for ground at BCM connector C2 pin A and connector C3 pin C1. If all check out, BCM is the culprit.

Also, the BCM controls the chime, fasten belts light, power door locks, hatch release, courtesy lamps, delayed int. lamps and the illuminated entry. Are any of these other functions not working properly?

Lastly, the BCM can flash it's DTC's by putting it into diagnostic mode. To do this, put KOEO. Then off.

Remove fuse 17 RADIO fuse from the IP fuse panel.

Turn key to ACC position and wait for 1 or 2 chimes.

Within 5 seconds, turn the key off then back to ACC it then chimes for verification it entered into dia mode 3

The BCM will then flash the DTC's with the security light within 4 seconds.

Each code is repeated 3 times before going to the next code.

good luck

Dave

Dave89IROC

now here is a question, does the security light come on for bulb check? if no, find out why(bad bulb?)

m0nk

Yes the security light does a bulb check, thanks for the imput slowpoke. Hopefully I'll get around to tesing out all of these things today along with a few more ideas we came up with. I'll get back to you later with all of it, and hopefully a working car if a pray enough :-)

forgot to mention, yes the int lights, dimming, chimes, power locks and such are all working.

m0nk

All the powers and grounds to the BCM check out.
When going to get the BCM to flash DTC's, I get up to turning the to the ACC, it chimes twice, i go back into off, then back into ACC but get no chimes.

Tomorrow I'm going to start looking for grounds that arent connected in my engine bay, I did a quick look today and it appears that they are all intact. The more we look over the problems the more we think its either a bad ground or power wire, making this harder to deal with. He says he wouldnt be suprised if it was a bad ground somewhere because of the problems alot of cars have with bad grounds. For example the C5's have a problem with a ground in the drivers side door that can set off over 30 trouble codes.