Hi, I bought a 96 Ranger 2.3L a few weeks ago and I'm a bit stumped with this one. I'm getting a p0340 code which I understand means the PCM is not getting a signal from the camshaft position sensor. I replaced the sensor and did a continuity check from the PCM to the sensor, and it all looks good. Then I put together a little oscilloscope out of an old Arduino to check the waveform. Not sure what its supposed to look like, but the waveform is the same at the sensor and at the PCM, so I'm sure the wiring harness is good. I read that a bad alternator could throw off the signals, so I threw on a new one on since the battery light was on anyway. The battery light went away, but the code did not. I've reset the PCM and the code still wont go away. I don't want to jump to conclusions about the PCM being bad since the car runs without any issues, but I'm all out of ideas. I haven't checked the timing because I feel if the timing was off, I'd notice it when driving the car, but so far its been driving completely normally. Please help not sure how to proceed with this one.

 

Welcome to the forum

P0340 Camshaft Position Sensor Circuit Malfunction

Good testing and troubleshooting

Yes, P0340 can be PCM(computer) issue
But best to eliminate other reasons first

If you have a scope to view analog signals then Google: How to fix code P0340. A new cam sensor will not repair this car.
Watch the video

It will show you what to look for, i.e. the signal pattern you should see and what you should NOT see, in this case AC Ripple
New alternator means NEVER EVER Tested alternator, so test it

Without a scope
Clear all codes
Start engine
See how long before CEL comes on and P0340 is set, should be quick
Shut off key
Clear code again
Unplug alternator's 2/3 wire connector(voltage regulator), so alternator is OFF LINE
Start engine, Battery light will stay on, that's OK
See how long it takes for CEL to come on or if it does come on and sets P0340 again
If it doesn't set P0340 again then new alternator has a bad diode, it happens return it

If P0340 does come back then since you have tested the wires and have a new Cam Sensor then most likely the PCM has an internal issue, you can pull it and inspect the circuit board, but most likely not fixable, there will be a part number on the label of PCM, F67F-12A650-??? or F57F-12A650-???
1996 Ranger 2.3l SOHC PCM doesn't have PATS(passive anti-theft system) so can be swapped easily

Try this site: https://www.car-part.com/

Good place to search for any used parts
1996
Ford Ranger
Computer box engine
skip areas
YOUR Zipcode
Search

New window opens
F57F or F67F can be used
"12A650" is not shown since its the same part number for a PCM on all year Fords and all Models, so has no meaning in a search for a matching PCM
The last 3 digits are what you want to match if possible, i.e. CCB, CCD, AYA, these are software versions
AT = automatic
MT = Manual
Also need to match that
Select a PCM from the list
Search

 

I disconnected the alternator and the code returned immediately, so seems the issue is in the engine computer. I went ahead and replaced the PCM, but it hasn't made a difference. Decided to check the timing since I've been avoiding it, but the timing looks good. Maybe off by half a tooth, hard to tell. Checked the reluctance wheel that the camshaft sensor reads and there seems to be no obvious damage. I must be missing something very simple, but I feel like I've checked everything there is to check
Camshaft sensor - replaced
Wiring to PCM - good
PCM - replaced
Alternator - replaced
Timing - good
Any ideas what else could be checked?

 

That's pretty much all there is

Check the old cam sensor with a VOLT meter, set meter to AC Volts, then pass a metal "tooth" in front of the end, i.e. metal screwdriver, socket extension, should see a slight AC pulse at each pass

If so then its a known good sensor, swap it in

Did you test for AC Ripple?
swapping in new parts(alternator) isn't the same thing