P0340 Camshaft Position Sensor - Already replaced the synchronizer. Ideas?

[nobb]

Hi guys,

I originally had a P0340 camshaft position sensor code pop up and the engine was shaking. Upon inspection, the synchronizer was good but the sensor cap seemed to have been contaminated with oil. I replaced the cap and all was good for a bit, but then the code popped up again (although the engine ran smooth this time). So I decided to replace the entire sensor and synchronizer with a brand new one. After a week, the same P0340 pops up again, but once again the engine runs smooth with no misfire at all (per my OBD scanner).

I'm completely stumped now. What else can I try to diagnose this further? Everything should be aligned properly and the engine runs completely smooth so I'm having a hard time figuring out what could be wrong.

Thanks!

 

[Eddo Rogue]

Did you replace it with an aftermarket synchro? If so, it went bad, do it again... this time with an OEM unit. I did. Had to track down an NOS motorcraft unit because they don't make em anymore for my truck. Got lucky on EBay.

 

[nobb]

Did you replace it with an aftermarket synchro? If so, it went bad, do it again... this time with an OEM unit. I did. Had to track down an NOS motorcraft unit because they don't make em anymore for my truck. Got lucky on EBay.

Nope, it's an OE unit.

 

[Eddo Rogue]

Nope, it's an OE unit.

Hmm ok. Did you lube the gear on it real good before installing? Might have gone bad again anyways...Besides that the only other thing(s) I can think of is either a bad coil pack or crank position sensor.

 

[nobb]

Yup it's all lubed. Also the coil pack was replaced a few months ago with an OE unit so pretty sure it's not that.

Didn't think a bad crank sensor would trigger the code?

 

[RonD]

What year 3.0l Ranger is this?

1995-1998 use 3 wire Cam sensor, Hall Effect type
1999-2008 used 2 wire Cam sensor, Variable Reluctance type

You may need to test the wires at this point

No, Crank sensor wouldn't be involved for a P0340 code
P0340 Camshaft Position Sensor Circuit Malfunction
This would indicate sensor itself or wiring issue, and can even be an inside the computer issue for this circuit


These could "possibly" involve Crank sensor since both sensors are compared for RPM and timing
P0341 Camshaft Position Sensor Circuit Range/Performance
P0342 Camshaft Position Sensor Circuit Low Input
P0343 Camshaft Position Sensor Circuit High Input

If you look up a code you should always look it up on a FULL code list first, the codes a computer does NOT USE are as important as the code it does use

 

[bills4065]

What RonD said. If you have access to a scope, you can do a signal check right at the PCM.

 

[Shran]

I have also heard that CMP sensor related faults can pop up because of a bad alternator... if it is generating enough AC voltage, it can confuse that sensor and cause issues with misfires and stuff too. I would have your alternator tested just to rule it out.

 

[RonD]

+1 ^^^

Forgot about that one
Alternators can leak AC Voltage, called ripple voltage, which will cause sensor issues in the computers system

Google: test alternator for AC Volts

 

[bills4065]

AC ripple test: run engine at 2000 rpm, Connect your voltmeter to the alternator BAT post and a known good ground. Set your meter on AC voltage, mine has a 2 volt setting. Maximum allowable average AC voltage is .3 volts. (300 mv.)

 

[nobb]

Thanks for the suggestions guys. I hooked up a battery tester with a crank and alternator (ripple) test. The AC ripple seems to be within spec.

Strangely the check engine light suddenly went off today and I didn't even clear the code. This is so weird.