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340 code reading- camshaft sensor?

Hello, I have a 1996 Ford Explorer XLT. The check engine light came on and lucky for me I have an electrician friend with a code reader that said 340, which is a camshaft sensor malfunction. I don’t know much about cars and don’t know what this means. The car seems to run fine. No strange sounds or weird behavior. Is this a dire circumstance?

The camshaft sensor synchronizes with the crankshaft sensor to determine when to fire the fuel injectors and for what cylinder. If this sensor fails, the computer will go to a default value to fire the injectors in order that engine still run. But when doing so, it will default to a rich condition. So you’ll see a slight drop in fuel economy. And if the engine is operated over an extended period of time under this default mode, it can result in damage to the catalytic converters.


" P0340 Camshaft Position Sensor A Circuit." The code says circuit, not malfunction. That seems like a difference, doesn’t it? The circuit includes other things than the sensor, itself—such as wires, connectors, the input to the engine computer, etc.
First, erase the code and wait for it to come back. It may not. If it does,
you might luck out if you throw a sensor at it; but, maybe not.

What size engine? It does make a difference. You need to tell us. Here are the instructions for test and replacing the camshaft position sensor (cmps):

It could be if this engine uses a camshaft synchronizer. I know on the 3 liter Vulcan engine the synchronizer drives the oil pump, so if the synchronizer gears fail you loose oil pressure. I am not sure about 4.0 and the 5.0 liter engines but I did find Cam synchronizers listed as a replacement part for both engines at

What usually happens is a bushing inside the synchronizer wares out causing it to wobble. This wobbling ruins the cam sensor on top of the synchronizer requiring both the sensor and synchronizer to need replaced. Only use a genuine Motorcraft synchronizer.

The engine is 8 Cylinders P 5.0L EFI.

That link is great! The engine is 8 Cylinders P 5.0L EFI.

So, the 5.0L camshaft position sensor (cmp) is mounted to the front of the engine on top of the camshaft synchronizer by two little 7/32" (5.5mm) screws.
IF you decide to change the cmp sensor, don’t automatically assume that the camshaft synchronizer is bad. DON’T remove the synchronizer if you are just changing the cmp sensor.
To remove the cmp sensor, remove the air cleaner housing; Disconnect the large water hose on the front of the engine; Catch the coolant; Carefully note, and mark, the position of the electrical connector “snout” on the cmp sensor. Disconnect and clean the connector with several blast of electrical contact cleaner inside the connector, and out. DON’T rotate the engine! You could test the wires for voltage and continuety, now, if you wished. Look at the small metal block (the sensor, actually), and at the projections (vanes) on top of the synchronizer and determine if they have rubbed. Feel for any sidewise play of the top of the synchronizer. If there is either, THEN, you replace the synchronizer If not, place, or replace, the cmp sensor, and install the two 7/32" screws; Reconnect electrical connector to the cmp sensor; Put the other stuff back, and see if the code comes back.