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Discussion Starter · #1 · (Edited)
Engine died recently with P0340 camshaft sensor code. Engine restarted, so erratic like many past engine-dies. Most other such sudden-deaths triggered a misfire code and were due to melted injector harness, crankshaft sensor, or wires in the main engine harness (pulled apart, found some wires stuck together but no exposed copper, rewrapped). Not all fixes assured.

Last pass with P0304, I loosened the sensor and pushed it down to touch the camshaft sprocket, then backed-off not even a hair as I tightened the bolt. No more issues for over a year. Of course, usually dies when wifey is alone. 3rd camshaft sensor. As best I recall, the OE sensor was the one I f'ed when I took a shortcut and left it installed when I put the timing cover back (new timing set and O-rings). It was broken from interference. I vaguely recall having changed that sensor before, though not in my notes, and bought the van used with no history so might have already been changed as-found.

The replacement sensor which triggered the current P0340 is Autex 115936, $16 Amazon. Embossed on it is " > PBT-GF30 < ". Autex claims to be a major manufacturer (supplier?). Office in Milpitas, CA (Silicon Valley) so perhaps just a Chinese importer. I installed a Standard Motor Products PC147 ($35 Amazon). Embossed on it are "13821" (with a "T" printed over the "3") and "1A". Amazon page stated "China", but came in "Hecho En Mexico" box which made me glad. SMP is a long-time supplier, but avoid their economy parts line (reboxed Chinese). I didn't choose the $65 Mopar branded sensor because others have state "Made in China". Engine started right up, but no assurance. I have read many reports of bad/suspect camshaft sensors in the 3.3/3.8L engines, but also true for many engines (dealt with same in my 1996 Plymouth 2.4L DOHC). Hopefully, as a team we can find ones that are robust, or if the problem lies elsewhere.

I'll report back if repeat problems. Besides the sensor itself, there could be problems in the wire harness, connectors, or the 8 VDC supply share with the crankshaft sensor and another device near front bumper (not in schematic, but found that wire going forward when I had the main harness open years ago). You can bench-test the sensor fairly easy. It is 3-wire Hall-effect type. You apply 8 VDC and gnd. Signal is from 3rd wire to gnd and should be digital ON (0 V) or OFF (5 V) as steel is moved near the head, unlike the raw analog signal from a 2-wire VR sensor. It has internal amplifiers. I'll bench test the Autex one when I get a chance, using a scope to insure no erratic pulses.

As a rant, this wasted-spark type of engine (coil-pack, 2 cylinders share a coil) could run fine without the camshaft sensor. It is only used for "sequential injection", which times the fuel pulses to intake valve opening. That only matters at short duty-cycle of the injector (low flow, near idle) since the intake valve is closed 75% of the time. Purpose is to reduce emissions around idle and perhaps very slight mpg improvement in normal driving. For some reason, the software disables the spark (via ESD relay to fuel pump?) if the camshaft signal is bad. I wonder if a Chrysler choice or EPA mandate. My 1996 Plymouth 2.4L DOHC (coil-pack) is the same - pull the camshaft sensor plug and the engine dies.
 

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Discussion Starter · #2 · (Edited)
Update. Did a quick bench test. I was wrong stating that the camshaft sensor has an internal amplifier which outputs a 0 or 5 VDC signal. Actually, it has just an internal transistor which conducts to ground. The PCM supplies 5 VDC on the signal wire thru a pull-down resistor. With sensor not installed, but connected to the engine harness with ignition on, if you back-probe the signal wire you should read 5 VDC (steady) with no metal and 0 VDC (steady) when steel is placed against the face. You can rig a simple bench circuit with 2 resistors to reproduce this. I should have watched youtubes first (below).

Initially, I rigged to read the signal output as if a voltage. That seemed to somewhat work as the old camshaft sensor gave no signal and drew no current from the 8 VDC power supply, and similar for an old crankshaft sensor. Also, that crank sensor felt no magnet force and the cam sensor only a slight magnetic force. Another crankshaft sensor (on bracket) gave a 12 mV signal increase when steel was placed at the face (from -6 mV without) and drew 12 mA. (Bracket is to mount on my 1965 Dart V-8 engine w/ 36-1 toothed wheel, but currently using a Ford VR sensor). I then changed to the youtube bench test of wiring two 10K resistors in series across the 8 VDC supply, with the signal wire connected between them (not shown, see youtube). That gave a 4 VDC signal which dropped to 0 VDC with steel at the face, for all 3 sensors. The signal dropped with the steel about 0.100" away (100 mil). The paper spacer is 0.030" thick (30 mil). So, all 3 sensors do work. Less assurance that the new camshaft sensor I installed will fix the erratic problem which occasionally kills the engine. One youtube (not linked) says that P0340 will often be triggered by a failing crankshaft sensor.

Note how the face of the cam sensor I removed was scored by the camshaft sprocket, a result of how I set it closer without a paper spacer. Perhaps stupid, but kept the engine working another year and was still running when I took it out.

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Circuit component Passive circuit component Hardware programmer Electronic component Electronic engineering
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I have found that auto parts store camshaft sensors (among others) do not work as well as OEM. My experience is the magnet in the OEM sensor is much stronger than non-OEM and that is where I believe the problem is. The signal is not strong enough to be reliable.

Bottom line, pony up the $$ and get an OEM sensor.
 

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It looks like something was rubbing the bottom of the sensor. I've used AutoZone brand sensors with no issues. It comes with the paper spacer too. Make sure the bolt is tight, not to tight, or the sensor will move and cause the engine to shut off.
 
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