Codes Everywhere (P0129, P0344, P0340, P0300)

FadeToGray

FadeToGray

TJ Enthusiast
Supporting Member
Joined
Feb 4, 2019
Messages
192
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NH
Was very excited to start up the Jeep this week after its been sitting for a while, and be greeted with a check engine light, and the 4 love letters below from my Bosch reader.

Has a harder time than usual starting, and drops RPMs. Sometimes it will stall and other times it just keeps dropping RPMs and then goes back to normal idle. 213K miles.

I installed a new NTK Map Sensor today, but that didn't do anything.

Something major going on here or should I just start replacing sensors and see if that fixes things?
  • P0129 - Barometric Pressure Too Low
  • P0300 - Multiple Cylinder Misfire
  • P0340 - No Camshaft Reference Signal at PCM
  • P0344 - Camshaft Position Sensor Circuit Inter
Everything seems to work fine and it ran great up until this week.

Thanks in advance for the help.
 
Wouldn't be the first time I fixed one thing only to have a completely unrelated thing break that I never even touched.

Occams razor may apply here. The map sensor & cam sensor both work off the same 5V reference signal, so maybe neither are communicating well with the PCM. The misfires could be because the cam sensor isn't communicating well. All the sensors use the same 5V signal, so if there is a short to ground somewhere they could all act up.

I would start by checking for good ground & good 5V reference with the key on at the cam & map sensors, and make sure there are no shorts across those wires. And then inspect the wiring at the plugs & sensors. In my experience that tends to result in a crank/no-start but I'm comfortable with a voltmeter so I'd look there first.

Firing the parts cannon is not usually the best approach, but the cam sensor is pretty cheap and easy to replace so I might just do that if the 5V/ground test looks low and there are no visible wiring issues there. At the very least you eliminate another variable.
 
Just wanted to close the loop on this post, it did end up being the battery and all the crud on it. Once I took care of that, all the codes disappeared.

Thanks for the help.
 
FadeToGray said:
Just wanted to close the loop on this post, it did end up being the battery and all the crud on it. Once I took care of that, all the codes disappeared.

Thanks for the help.
Click to expand...

Did they just disappear because you had the battery disconnected?
 
They haven't come back yet, the hard start, and the RPMs dropping to almost a stall at idle is gone. So I'm hoping not.
 
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