1997 Cavalier 2.2 OHV
149,000 KMs
About 3 weeks ago, I had my negative battery terminal pulled for a few minutes to do some wiring with my audio system in the trunk. When I was done, I had a check engine light, and it has persisted ever since. Car runs fine otherwise.
I borrowed a basic code reader and it's throwing P1336 - Crankshaft Position System Variation Not Learned. Clearing the code simply causes it to recur immediately. From the notes I've read online, this suggests that I've managed to wipe the supposedly "non-volatile" memory in the ECM that stores baseline crank position data. The only prescribed fix I've seen is to perform a relearn procedure with help of a GM Tech II unit.
Three questions:
1) Does this problem suggest anything I could have done differently or should avoid to prevent this happening again? Surely not everyone has had to run to their dealer for a Tech II every time their battery is dead or disconnected.
2) Does anyone know of a way to deal with this problem without special equipment?
3) Should I be wary of a bad crank position sensor? It doesn't seem like this should be the cause, or should fix the problem, but perhaps this is a sign it needs doing?
Thanks for any input.
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I think in a case like that you HAVE to do the relearn, and you need special tools to do it....it is not like doing a specific drive cycle will reset it. I have not heard of a bad crank sensor causeing that light. Usually a bad crank sensor will not allow you to start the car.
You may be able to do it with HPT if you or someone you know has it. I do NOT know if this feature would require you to license your car with the software though.
This problem does NOT occur everytime you replace something, or disconnect the battery, but CAN occur if you change cam, crank, cam sensor, crank sensor, engine....blah blah.
To be safe in the future, remove the trunk light bulb, and use a battery backup that plugs into your lighter with a 9v battery. This will keep all your memory in tact while the battery is disconnected, but if a dome or trunk light is on, it will burn through the power source very fast.
Thanks for the informed response. You certainly have a point about the crank sensor. The car runs fine, so that pretty much guarantees it's still providing good data. I hadn't thought of a backup battery -- good thought.
I'm still a bit annoyed that this supposedly "protected" memory area erased on me, and I'd sure like to know how I managed to do it. I certainly didn't have the engine apart, and "non-volatile" memory by definition shouldn't care where there's a battery attached or not. What's more, I've had the battery disconnected dozens of times previously. Go figure.
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