P0300, P0129, P0108 Codes

Tiny
6LAXICAN
  • MEMBER
  • 2006 DODGE MAGNUM
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
So I bought a 2006 dodge magnum 5.7 hemi station wagon but upon purchasing the car the owner instructed me that he had placed a 5.7 hemi 2006 Chrysler 300 motor heads inside the car but the manifold is still dodge magnum, so these codes are coming up and I'm assuming from the high voltage reading I'm getting on the continuity test for the sensor it's not dropping in volts to about one or two it's going up from 4.8 to 4.9 so I'm assuming the OEM harness or the wiring harness for the engine is not compatible for the Dodges computer since the rest of the car is still the Dodge Magnum and the only things that are the Chrysler 300 says the engine and hands so my assessment is that the harness is bad and I don't know which harnesses on the car so I need to replace the harness but I'm thinking it has to be a dodge 5.7 hemi 2006 harness so it be compatible with the Chrysler 305.7 hemi engine and hands why the guy didn't keep the 5.7 hemi manifold for the Chrysler 300 I will never know but help me with the situation because I can't keep spending money on parts. Please and thank you for your assistance and I promise to donate at gofundme if this is a real mechanic. Please no bots.
Saturday, August 23rd, 2025 AT 10:03 AM

1 Reply

Tiny
MECHTRIX
  • MECHANIC
  • 382 POSTS
Ok I can help you
with these 3 codes
the cars most likely running lumpy jumpy and grumpy right now let's figure it out. In this case trust these codes

Code number 1.
Po300. Random misfire can be cuased by many things but likely cuased by the other 2 below
Hint"
some of the things that can cuas this well be checking anyway for the other 2

Code number 2
Po129 (pressure to low) the barometric /baro pressure sensor is a sensor that measures ambient air pressure outside the engine like the air we breath mostly for altitude changes
its repoting that the barometric pressure is to low theres a good likelyhood its related to the one below becuase. Its saying the pressures to low for the thjngs going on inside the engine sometimes the 2 sensors are working together one up it but if it has a seporate baro sensor thats OK too becuase these checks are for both either way.

Check for loose or damaged or dis connected wires for this sensor its usually located on the manifold. If all looks good go to the next check

Code number 3
Po108 now this is key"i believe this is where most if not all of the problem is. Becuase influincees the way things adjust for whats going on inside the engine it's related to a signal the ecu is recieving [voltage singal to high ) from the map sensor. This is probably a bad sensor so in this case it really effects the way the engine runs
It can be causing the other two problems above
From my experience if this problem is solved it will likely eliminate the other 2 it's located on the intake manifold.

So first check all wiring for any damage cracked broken loose dis connected for this sensor first then at this point any others thoughout the engine bay while you're looking around.

Then check
all vacuum hoses theyre important
If theyre bad fix repair replace any and all of the bad ones. Then might as well check all the ones you find anywhere in the engine bay
After that
If you checked all these things and don't find anything wrong and it's decided that
theyre all tight clean and connected well can't find anything wrong than

(Replace the map sensor.) It's likely bad
They're not to expensive and easy to change
If replaced
Erase the codes and start a new drive cycle my guess is all 3 codes will not re appear again and the car will run good again but keep in mind there's alot of mismatched parts on it so keep an eye on it good luck hope this helps
Was this
answer
helpful?
Yes
No
Saturday, August 23rd, 2025 AT 3:08 PM

Please login or register to post a reply.