Cam sensor, help?
just this summer my cam sensor went bad. my car would have trouble starting and the tachometer was completely dead, the tachometer never went crazy while cranking over like you said. i changed the senser out for a new one and everything has been fine since then.
12 Second Club
Joined: Feb 2007
Posts: 150
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From: Fairfield, Cali
Actually you need the cam senor to start the car because the PCM will not know where TDC is at on cyl#1.. If you cam senor went out while you were driving it will still work as long as you don't turn off the car. But if you do, it won't start after that.
I was hunting down a nice problem that took a long time to figure out. Car just died at the 1000 foot, would randomly start. Sometimes it would run until a load was put on it, sometimes not at all. It was the crank sensor. I was told it will run based off the crank sensor, cam sensor or not. And it will go back to last known good timing.
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12 Second Club
Joined: Feb 2007
Posts: 150
Likes: 0
From: Fairfield, Cali
Not what Ive been told by some fairly smart gents....
I was hunting down a nice problem that took a long time to figure out. Car just died at the 1000 foot, would randomly start. Sometimes it would run until a load was put on it, sometimes not at all. It was the crank sensor. I was told it will run based off the crank sensor, cam sensor or not. And it will go back to last known good timing.
I was hunting down a nice problem that took a long time to figure out. Car just died at the 1000 foot, would randomly start. Sometimes it would run until a load was put on it, sometimes not at all. It was the crank sensor. I was told it will run based off the crank sensor, cam sensor or not. And it will go back to last known good timing.
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Joined: Apr 2002
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From: So.Cal.
From the GM Service Manual:
Crankshaft Position Sensor
...
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-synchronizes to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
Camshaft Position Sensor
...
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-synchronizes to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
(both sections contain the same verbatim).
Crankshaft Position Sensor
...
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-synchronizes to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
Camshaft Position Sensor
...
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-synchronizes to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
(both sections contain the same verbatim).
