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Discussion Starter · #1 ·
Hi guys, I'm new here.

So I bought this car as a project for my self. It's a 3.9 07 convertible with the minor issue of not being able to start.

When I bought it. It said 'error' in odometer and the wiring harness was a mess. I fixed the wiring and got the Pcm repaired. After a relearn process there are no error message and I'm being able to read data with a obd2 reader.

Everything seems to be better now but currently the car is not able to crank or start. The starter motor works, also starter relay and starter fuse are OK. If I jump the relay it does crank but no start. So next mission is to find why I have no crank when the key is on the On position.

What conditions needs to be accomplished for the Pcm to send the ignition command?

Thank you in advance for your help.
 

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Discussion Starter · #3 ·
Well, if I move the stick to P, the locks pop up by themselves, how can I make sure the transmission is in Park position?
 

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The PCM has to sense it electronically. The selector can be misaligned and you can also have wiring issues (broken wires, shorts, floating ground). Hope this helps.
 

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Discussion Starter · #5 ·
Everything seems to be OK with the shifter cable. While the car is in park you cannot move the car and also from D to P the locks pops by themselves.

What should be the next thing to check?
 

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Hi guys, I'm new here.

So I bought this car as a project for my self. It's a 3.9 07 convertible with the minor issue of not being able to start.

When I bought it. It said 'error' in odometer and the wiring harness was a mess. I fixed the wiring and got the Pcm repaired. After a relearn process there are no error message and I'm being able to read data with a obd2 reader.

Everything seems to be better now but currently the car is not able to crank or start. The starter motor works, also starter relay and starter fuse are OK. If I jump the relay it does crank but no start. So next mission is to find why I have no crank when the key is on the On position.

What conditions needs to be accomplished for the Pcm to send the ignition command?

Thank you in advance for your help.
So, there are a number of reasons why the car won't start, and it is possible to narrow down the causes fairly quick:
But before I list the reasons, you mentioned something about repairing the PCM and doing a relearn. I am not sure what you meant by repairing the PCM. But usually they need to be reprogrammed according to instructions, and a simple relearn procedure that you do yourself without the aid of a bi-directional scanner isn't enough. It requires what is known as tech 2 or GM MDI GDS2 as well as a paid one time access subscription to the SPS (GM Software Programming Service) at ACDelcoTDS.com (alternatively, you could get GM to reprogram it for you, uness you have a friend who could help you do it). The Module disables the car if it is damaged or not programmed accordingly. Having said that, let me list the causes:
1. PCM relay, starter relay and run/crank relay (main junction box)
2. Ignition/crank-run fuse (cabin fuse box (next to BCM))
3. Battery not having sufficiant amperage
4. Aletrantor damage
5. Altarnator-Battery fusible link Wiring damage
6. Starter-Battery wiring and or terminal damage
7. Starter or starter solenoid (including connectors and wiring) damage
8. Ignition switch circuit or wiring damage (test pink wire to starter solenoid)
9. Neutral Park Safety Switch damage
and finally, as you mentioned the PCM itself (it provides grounds in the initial starting of the car)


Verify the above one by one so as to not having to do more than you really need to. If you are in doubt, I recommend you view each component in a circuit electrical diagram. diagrams show wiring colors and circuit numbers and can be linked between multiple diagrams. Verifying the above will surely get the car started
 

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Discussion Starter · #7 ·
Ok. I already fix it. And yes. You can repair any electronic device, even a car computer, and since the repair was only replacing a voltage regulator there was no need to reprogram since the memory remains untouched.

This a review of what I have done in order to get it fixed and running.

1. Car was bought not running, not even crank and "error" on odometer. Wiring was a mess and cables was exposed to the engine heat. Also I was not able to read the DTC codes via obd2 reader.

2. Wiring was checked and repaired but the problem with "error" on odometer remained present.

3. PCM and BCM were inspected by an automotive repair shop and they found the Pcm was not being powered. So they replaced a voltage regulator and told me to connect everything back and execute a relearn procedure. Which is put the key in "on" position 10 minutes. Remove the key for 5 seconds and repeat the process 3 times.

4. After connect everything back the "error" message disappeared and I was able to communicate with the PCM and read codes and check live data from the computer, but there was no crank or start.

5. After checking the ignition wiring diagram and track the voltages and check the park neutral switch, I find there was a bad connection between the coil pins on the relay 31. I helped the relay by forcing the legs to touch the socket pins. And the car started. For the first time since who knows when.

6. Some new codes showed up in the scanner. And I was suspicious about if more relays and fuses would have the same problem as the relay 31. So I decided to get another fuse box at the junkyard and installed it on the car.

7. Several codes and functions disappear after installing the new fuse box and the car run smoothly.

8. Few codes remained but they are related to the fact that there is no catalytic converter Installed.
 

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Ok. I already fix it. And yes. You can repair any electronic device, even a car computer, and since the repair was only replacing a voltage regulator there was no need to reprogram since the memory remains untouched.

This a review of what I have done in order to get it fixed and running.

1. Car was bought not running, not even crank and "error" on odometer. Wiring was a mess and cables was exposed to the engine heat. Also I was not able to read the DTC codes via obd2 reader.

2. Wiring was checked and repaired but the problem with "error" on odometer remained present.

3. PCM and BCM were inspected by an automotive repair shop and they found the Pcm was not being powered. So they replaced a voltage regulator and told me to connect everything back and execute a relearn procedure. Which is put the key in "on" position 10 minutes. Remove the key for 5 seconds and repeat the process 3 times.

4. After connect everything back the "error" message disappeared and I was able to communicate with the PCM and read codes and check live data from the computer, but there was no crank or start.

5. After checking the ignition wiring diagram and track the voltages and check the park neutral switch, I find there was a bad connection between the coil pins on the relay 31. I helped the relay by forcing the legs to touch the socket pins. And the car started. For the first time since who knows when.

6. Some new codes showed up in the scanner. And I was suspicious about if more relays and fuses would have the same problem as the relay 31. So I decided to get another fuse box at the junkyard and installed it on the car.

7. Several codes and functions disappear after installing the new fuse box and the car run smoothly.

8. Few codes remained but they are related to the fact that there is no catalytic converter Installed.
Bravo! good job. Actually, you reminded of the time I had to do the same exact repair minus the ECM problem. It started out with no crank no start then replacing the entire junction box (I got lucky though I didn't have to replace the C4 C3 and C2-C1 panels). You also did good repairing an exposed to heat harness. I had to do the same. I have no idea what they were thinking when they wired this starter and alternator to the battery (among other connections) right agaisnt the 1200 degrees Bank 2 catalytic converter. You must be feeling pretty good after all that mysterious no start. I am glad you shared your experience.
 

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Ok. I already fix it. And yes. You can repair any electronic device, even a car computer, and since the repair was only replacing a voltage regulator there was no need to reprogram since the memory remains untouched.

This a review of what I have done in order to get it fixed and running.

1. Car was bought not running, not even crank and "error" on odometer. Wiring was a mess and cables was exposed to the engine heat. Also I was not able to read the DTC codes via obd2 reader.

2. Wiring was checked and repaired but the problem with "error" on odometer remained present.

3. PCM and BCM were inspected by an automotive repair shop and they found the Pcm was not being powered. So they replaced a voltage regulator and told me to connect everything back and execute a relearn procedure. Which is put the key in "on" position 10 minutes. Remove the key for 5 seconds and repeat the process 3 times.

4. After connect everything back the "error" message disappeared and I was able to communicate with the PCM and read codes and check live data from the computer, but there was no crank or start.

5. After checking the ignition wiring diagram and track the voltages and check the park neutral switch, I find there was a bad connection between the coil pins on the relay 31. I helped the relay by forcing the legs to touch the socket pins. And the car started. For the first time since who knows when.

6. Some new codes showed up in the scanner. And I was suspicious about if more relays and fuses would have the same problem as the relay 31. So I decided to get another fuse box at the junkyard and installed it on the car.

7. Several codes and functions disappear after installing the new fuse box and the car run smoothly.

8. Few codes remained but they are related to the fact that there is no catalytic converter Installed.
good job
 
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