Rick Cruz

Hello, need help on my 2002 Suburban with hard starting. Had a code p0343 cam position sensor. I replaced sensor and still hard starting and SES light comes back while cranking. I checked fuel pressure and has good pressure. Would crank position sensor contribute to the problem? I did test pigtail on Cam sensor and I do have 12 volts and good ground at sensor.

Any Help be greatly appreciated

repairman54

P0343 CHEVROLET Meaning The Camshaft Position (CMP) Sensor sensor works in conjunction with a 1X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12 volt power supply to the CMP sensor as well as a ground and a signal circuit. The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 1X signal in combination with the Crankshaft Position sensor 24X signal in order to determine crankshaft position and stroke. This diagnostic for the Camshaft Position sensor tests for a loss of Camshaft Position sensor signal. Observe that as long as the Crankshaft Position sensor 24X signal is available, 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 incorrectly synchronized to the exhaust stroke and will re-sync to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
https://www.engine-codes.com/p0343_c...is%20condition.

tech2

ohm check the signal wire from the sensor connector to the pcm connector

Rick Cruz

what would the ohm reading be? also would crank position cause hard starting?

Rick Cruz

Would a crank sensor possibly the cause of my hard starting.. I did change the fuel pump and filter since I retested the fuel pressure and it was low.

Any Help greatly appreciated

tech2

cam sensor would cause a long crank time. The purpose of the cam sensor is to tell the pcm the which cylinder is where for the purpose of spark and fuel injection. without this signal the pcm must use the crank signal....but the engine must rotate longer due to the build of the tone wheel. a crankshaft position sensor signal fallout would cause a no start.

what is the fuel pressure?
if the wire is good... you should get 0 ohms.

Rick Cruz

Do you know what pin # or a diagram to check OHM on PCM. If I didn't get 0 ohms where do I go from there. I did check voltage into sensor as well as ground. I changed fuel pump and filter out but only getting 52 PSI

Rick Cruz

Hard starting doesn't happen at every crank. I also noticed that I would get a slight back fire when its trying to crank.