[Stinkbait]

First time post so I'm not for sure if I'm in the right place. A couple of weeks ago my truck just out of the blue decided not to start. At first I think fuel pump, but was relieved to find out it working just fine. I then went into the ignition system checking spark plugs. They were not firing. Followed up the chain to the distributor and still no spark. Went to the ignition coil and still no spark. I change the ignition coil. Truck fires right up with no hesitation at all. I let it run for about 15 minutes and then turn it off. When I tried to restart the truck, nothing. Just the engine turning over without fire. A few days later (bad weather and stuff) I return to find while trying to start my truck the battery has run dead. So I head to the parts store and they charge the battery (they also checked the batt and it was fine, just no charge). The next day I pick up the battery and put it in my truck. I didn't think my truck would start but what the heck. I turned the key over and it fired right up. Again I let the truck run for about 10-15 minutes, turn off the truck, and it never restarted. At this point I'm thinking maybe a code in the ECM is keeping the truck from starting and that having the battery off for a day reset the memory. So today I decided to buy a OBDI scan tool (cheap one) and check codes. When I plug it in, according to the directions, the "Service Engine Soon" light is suppose to blink at least code 12. My shift light comes on(truck is a 5 speed in nuetral), my check gauges light comes on, and service engine soon. None of them blink. Instead the SEC light is staying on constantly. Not knowing what to do, I followed the directions in the manual on how to reset the memory via the scanner (by unplugging the fuses). When I do this the truck started right up again. But again when I tried to restart it, the engine turns over but the truck isn't starting. My brother-in-law and I were looking around the internet yesterday and signs seemed to point to a bad ECM since there are no codes coming up. Does anyone else think this could be a possibility? If so, wouldn't the engine still run, but just very badly? Does anyone have any ideas? Sorry for the long post. I have a 4.3L TBI 94 S10.

 

[octaneman]

Hi Stinkbait


A bad computer will give a code 66 and up but you have indicated in your post that the check engine light will not give any codes at all. The check engine light has to stay on for 3 seconds when the ignition is turned on. This is the delay that primes the fuel system and then it turns off, if it doesn't then the relay is malfunctioning. You will need to test the ignition relay and then check the wire connections from the computer to the ALDL connector, from your description it appears that there is no communication on the ALDL bus line to your scanner. The thing you need to know is that not all generic scanners can communicate with the computer, the scanner has to be CAM BUS compliant so do a little research on its capabilities or else the computer and scanner won't mesh. If everything does check out OK, then there is a strong possibility that the computer's PROM is gone.


post back your findings.

 

[Fred Garvin]

I would at least test your ignition control module. Many parts stores can do it. You can pull stored trouble codes w/o a scanner. With the ignition ON, jumper pins A & B with a paper clip. The initial Code 12 flashes 3xs indicating the diagnostic mode is working, then any stored codes will display 1 at a time.

If you can't get a code 12 to flash, you'll probably need a service manual to trace the problem.