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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 6924
Experience:  ASE Certified Master Technician
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Chevy blazer: Hey my name is***** have a 99 chevy blazer

Customer Question

Hey my name is***** have a 99 chevy blazer 4.3 I have the same p 0340 code, I've replaced the distributor the correct way TDC and pointer is right on mark on dist. New wires cam pos sensor and plugs still gave me p0340
Submitted: 1 year ago.
Category: Chevy
Expert:  Mike S. replied 1 year ago.
First of all, make sure there is voltage to the sensor, so disconnect the wiring harness and turn the key to run but don't start the engine.
You could use a 12 volt test lamp for this or voltmeter on dc scale.
Test the sensor ignition positive voltage circuit first and make sure you have voltage there. Then test the ground circuit and attach the test light to a B+ or the battery positive. The test light should light.
Expert:  Mike S. replied 1 year ago.
The positive wire should be the pink wire. It is fed from the ENG 1 fuse, so if there is no power check that fuse.
The ground appears to be the pink/black wire.
Customer: replied 1 year ago.
I check the plugs ground and it is good I have no voltage at plug with key on and eng1 fuse is good and has voltage
Expert:  Mike S. replied 1 year ago.
If the eng 1 fuse has voltage on both sides of the fuse with the key on run, and there is no voltage at the camshaft sensor plug, then there is an open or short in that wire. You may want to run a new wire but you really should find out where that wire is shorted if it is shorted just to be sure it doesn't cause other problems or start a fire.