TJ: P0340 Code ???

[Mike]

Okay, I'm having a WTF moment...

My 99 TJ 6cyl engine has thrown a P0340 code twice now. The code is a 'Camshaft Position Sensor Circuit Malfunction'. As far as I can tell, my engine doesn't have a Camshaft Position Sensor. I can't find any at the parts stores for my model, and nothing is mentioned in my Haynes book.

Any ideas on this one??

[Black & Tan TJ]

I think I had the same code but it was a misfire #4 cyl.

[aw12345]

It has a sensor in the distributor to synch the injectors and yes you could call it a cam sensor since it's camshaft driven. Just looked it up in the factory manual; for a 1999 tj and it's correct, no camshaft signal at ecm. Which essentially means it's not synching the fuel injectors correctly and basically runs in limp mode when that happens

CAMSHAFT POSITION SENSOR—PCM INPUT
A sync signal is provide by the camshaft position
sensor located in the distributor (Fig. 3). The sync
signal from this sensor works in conjunction with the
crankshaft position sensor to provide the Powertrain
Control Module (PCM) with inputs. This is done to
establish and maintain correct injector firing order.
Refer to Camshaft Position Sensor in Group 8D,
Ignition System for more information.

CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the distributor
on all engines (Fig. 2).
The sensor contains a hall effect device called a
sync signal generator to generate a fuel sync signal.
This sync signal generator detects a rotating pulse
ring (shutter) on the distributor shaft. The pulse ring
rotates 180 degrees through the sync signal genera-
shaft
position sensor to differentiate between fuel
injection and spark events. It is also used to synchronize
the fuel injectors with their respective cylinders.
When the leading edge of the pulse ring (shutter)
enters the sync signal generator, the following occurs:
The interruption of magnetic field causes the voltage
to switch high resulting in a sync signal of approximately
5 volts.
When the trailing edge of the pulse ring (shutter)
leaves the sync signal generator, the following occurs:
The change of the magnetic field causes the sync signal
voltage to switch low to 0 volts.

[Mike]

Awesome! Perfect Art. I really need to invest in a service manual eventually. But using what you gave me, my Powertrain Diagnostics manual now makes sense! Unfortunately, there are three pages of tests to puzzle my way through. Even so, I feel a hell of a lot better about digging in now.

[aw12345]

Awesome! Perfect Art. I really need to invest in a service manual eventually. But using what you gave me, my Powertrain Diagnostics manual now makes sense! Unfortunately, there are three pages of tests to puzzle my way through. Even so, I feel a hell of a lot better about digging in now.

Start at the sensor and go from there, hall effect sensors do fail or don't work when there is no voltage to them.
Look at the window thing also, burrs on that will wig out the signal