My 2003 Suburban with 175,000 miles would sometimes continue to run after I turned the ignition off and removed the key. I had to remove the fuel pump relay to stop the engine. When i restarted the truck, it would be in limp mode, throwing codes 740, 752, 785 and 1860. I would clear the codes with my OBD unit and the truck would run normally for a while. Sometimes the battery would be dead the following morning.
The problem was intermittent for about 6 months and in the last few days the truck would never shut off when I attempted to shut it off with the key.
I called the local Chevy dealer and described my problem and he said he had never heard of it but thought he could diagnose and fix it for $200 to $1,000.
After searching the internet, I replaced the ignition switch and the key lock cylinder. The problem was still there.
I then googled "car won't shut off" and found an article saying the problem may be a bad diode in the alternator allowing continuous current to the ignition.
You can determine if it is the alternator quickly and easily by popping the hood and unplugging the three wire connector that goes to the alternator at about the 11 o'clock position. With the three wire connector unplugged, start and shut off the vehicle. If the vehicle shuts of as it should, you have found the root cause.
In my case, I replaced the alternator and all is good. I had installed a Reman Duralast alternator from Auto Zone abut a year ago.
The ignition switch and key lock cylinder are very straightforward and easy to replace. Just watch the youtube videos.
i hope this helps a few people with vehicles that will not shut off.
The problem was intermittent for about 6 months and in the last few days the truck would never shut off when I attempted to shut it off with the key.
I called the local Chevy dealer and described my problem and he said he had never heard of it but thought he could diagnose and fix it for $200 to $1,000.
After searching the internet, I replaced the ignition switch and the key lock cylinder. The problem was still there.
I then googled "car won't shut off" and found an article saying the problem may be a bad diode in the alternator allowing continuous current to the ignition.
You can determine if it is the alternator quickly and easily by popping the hood and unplugging the three wire connector that goes to the alternator at about the 11 o'clock position. With the three wire connector unplugged, start and shut off the vehicle. If the vehicle shuts of as it should, you have found the root cause.
In my case, I replaced the alternator and all is good. I had installed a Reman Duralast alternator from Auto Zone abut a year ago.
The ignition switch and key lock cylinder are very straightforward and easy to replace. Just watch the youtube videos.
i hope this helps a few people with vehicles that will not shut off.
