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Ok so 2001 C5Z. Car has been having an issue where it would try to die while I was driving. Usually just at tip in or anytime it was a large transient at low rpm. I decided to clean the TB and the chassis grounds hoping that would help. After that, the car would crank and not fire. BlueblownZ06 helped me diagnose it and we figured out the ignition switch was a problem. So I used Bill Curlee's thread and repaired it. Now the car fires up as long as it has good voltage, but after a bit it just dies like someone cut the fuel or spark. I'm waiting on replys from Bill and BlueblownZ06 right now.
I just tried that, no change. However I pushed the key in tightly and it started up for me. I'm thinking the key plunger connection points might be the issue.
Ok the tan wire at the ignition switch reads 2 volts less than the rest of the hot leads with the switch to the on position. At the cluster it reads almost zero volts.
Please explain what/where you are measuring. I don't follow you with "at the cluster".
The brown wire splits out of the ignition and goes to 2 different pins on the BCM. I would think the reason the voltage is low is because of pitting or carbon on the contact surfaces inside the ignition switch that relate to the tan wire. Might be ground G202 which grounds that circuit. Since post #1 indicates that you repaired the ignition switch perhaps the surfaces dealing with the TAN wire are still problematic??
You also indicate you serviced grounds. Did you do G202???
Here are two links about grounds and their locations and what is grounded at each location:
No I haven't done any of the interior grounds, just the engine bay. The tan wire corresponds to the engaged contact when the key plunger is in the down position. I just rechecked the ignition switch and found resistance on both sides of the key plunger circuit. I'm just wondering how that lead could be hot if the key is in and in the on position.
"At the cluster" I was talking about the tan wire that goes into the 4 wire star cluster. I assumed it corresponded to the tan wire that connects to the ignition switch. I noticed it comes through the BCM first.
IDK where to start. Still having issues. I can get it to start once in a while now. I've replaced the ignition switch and cleaned up g106. I also checked every injector and coil hot lead as well as all fuses related to bcm, pcm, coils and injectors. I've also swapped the ignition relay. Yesterday I pulled the battery tray and found some battery acid damage to the paint on the frame rails. I also see residue on the harnesses and PCM. So I started digging into that. I exposed the pcm to engine harness and haven't found any damaged wires. I also removed the PCM cover and it doesn't look like anything got past the seals.
If the car starts and runs, when it shuts down it will not start again for a while. I've tried to test the coil and injector circuits while it dies, but thats proved illusive. The amount of run time I get when it does start is inconsistent. Sometimes it'll die as soon as it idles down, sometimes it makes it into closed loop mode and then some.
I'm totally lost.
Yes, monitored fuel pressure quite a bit. With the pump priming it jumps as high as 62psi then drops to 58 and holds. While cranking it holds at about 62 and once it starts it drops down to about 58-59 and holds. The car has just over half a tank. The injectors are getting voltage. The only thing I haven't done Is bench test the injectors. That's on my to do list once I clean up the battery acid damage.
Cleaned up the acid mess and rewrapped the wiring harness and reinstalled the PCM. Bench tested and cleaned the injectors. Still no change. Next step is to clean the connectors at the starter.
Ok so went back and bench tested the injectors under rail pressure, they fire great. Decided to check the voltage across the injector plug while cranking and it's only pulsing up to about 6 volts. Not enough to fire them under rail pressure. Just to test that theory, I used a 6 volt battery to bench test one under rail pressure and it didn't have enough juice to fire. Went back and checked voltage at the fuses and got battery voltage for fuse 18 and 22. I pulsed a little fuel into each cylinder and the car fired up. Wouldn't idle though, kept getting like a stuttering like when there is a loose connection. Right now I can't get the diagram Bill sent me to open though. I'm thinking definitely a short somewhere between the fuse block and the injectors. I've had the harness open all the way from the pcm to the where it leaves the battery compartment area. I guess now I'll be opening up the rest. Given that all injectors are affected, I'm assuming the pink wire is shorted somewhere.
As I mentioned in our private discussion, I've seen defective, high resistance connections in the fuse blocks before that will cause low voltage under load and look good when you check it at the fuse. I recommended getting a good meter that will show min/max values across the injectors and test that. I would also consider jumping a fused hot wire to the pink wire off the power distribution lug or battery hot to see if that solves it. If so, you can rebuild the circuit by running a 30amp fused hot to a relay, pin #87, tap into the pink wire at the ignition switch and run it to pin 85, ground pin 86, and run pin 30 to your injectors and coils. We'll get this figured out.
Hey thanks again for helping me figure out the problem, that's the first time I've felt completely lost diagnosing a problem. I guess that's why I'm studying mechanical not electrical engineering.
08-21-2015, 05:43 PM
Car idles then dies.
