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P0300 Diagnostic Steps \ Ideas

12K views 14 replies 4 participants last post by  mauiadmin 
#1 · (Edited)
What up Cali folks.
My poor 2007 SE 2.0 is having a P0300 Random Misfire issue.
Monday, the car lost all performance and went into limp mode, flashing CEL while driving on the interstate.

I parked it near the next exit and pulled the codes. (I keep an ODB2 reader on hand)
At that time it was showing the code for Crank Position Sensor circuit failure.

I reset the faults codes, pulled the negative battery terminal and let it sit overnight.
After running around town to find the part, I replaced what looked to be the OEM sensor.

This car has served me well and is currently sitting @ 220,000 Miles.

After installing the new sensor, restoring the battery power and starting the car all was good.
No CEL and running well.

I drove about 2 miles and up pops CEL with error P0300 and limp-mode.
I reset the codes again, pulled the power and let it sit for 30 minutes.

Same status P0300.

What's strange is that after resetting the codes and starting the car it will idle perfectly firing on all 4 indefinitely. (Or at least the 10-15 minutes I've let it sit there)
I even tested each cylinder by disconnecting the coil on each plug to ensure it was dropping the cylinder.

Each disconnected plug reacted exactly as expected, no fire, plugged back in the cylinder fired again.

The P0300 only pops up when you attempt to get it to 2,000 rpm.
I'm able to monitor some of the simple features of the engine with the code reader I have and an application on my PC.

Tonight I'll have a chance to get my meter out and test fuel injector power and\or fuel pressure during increased throttle.

Does anyone have 2-bits they want to throw in?
Other than this the car has been perfect with no other issues. :-\

Maybe fuel pump issue, Cam-Position-Sensor?

Thank you very much. -Chris
 
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#2 ·
All you mentioned and then some. The service manual even lists the fused main relay output circuit. I suggest you download the free copy of the service manual. Links are in our "Manuals" sub-forum.
 
#4 ·
There are 2 Camshaft Position Sensors. You need to replace both at the same time and battery needs to be disconnected when you do it. If not, the new ones will not be seen.
 
#6 ·
Yup. One up at the front of the engine, and one at the backend. The service manual shows where both are located.
 
#7 · (Edited)
I have reviewed the service manual and I'm pretty sure they're considering the crankshaft sensor as the 2nd camshaft sensor. Under the Ignition Control section it lists the cam and crank but whenever you look at the removal\installation instructions it doesn't show anything about the crank but the location looks to be exactly where the crank sensor is.

I called a couple parts stores and they show the car requires only 2 sensors 1 crank and 1 cam position sensor.

I have spent a day testing everything I'm capable of doing with my test light and meter.

The sensors have the proper stable voltage, the coils have power, I've swapped their locations, the injectors all have voltage.

I'm leaning towards a bad PCM possibly.

As noted in my pictures, whenever I review the timing, RPM and throttle position etc. they're all over the place. The RPM bounces from 600 to 8,000 back and forth. (Even though the engine isn't revving up and down)

Maybe it's my code reader but I can't be sure.
I guess my only choice is to take it to someone with a real deal computer who can look deeper into what is and isn't reading correctly.









The pictures have been squeezed for some reason so here are the links:

Low RPM
https://lh5.googleusercontent.com/-Fk91OnSD5ns/VDrcGX7tc8I/AAAAAAAADRM/FvrQGlMebMU/s800/LowRPM1.png

High RPM
https://lh3.googleusercontent.com/-6MHLT4LdIIQ/VDrcGNvcGdI/AAAAAAAADRE/09C5NVZM3eM/s800/HighRPM.png

O2 Sensor \ LAMBDA Readings
https://lh5.googleusercontent.com/-1JPai9aXdY0/VDrcGQUNokI/AAAAAAAADRI/vDf7GJSmMIk/s800/O2Sensor.png

MAP Sensor
https://lh4.googleusercontent.com/-TJrLcPlOfW4/VDrcGiK_-7I/AAAAAAAADRQ/cX2Jr-NMCHo/s800/Stats.png
 
#8 ·
Page 8i-42 covers BOTH the front and rear camshaft position sensors. Page 14-57 covers the crankshaft position sensor.

The manual is poorly laid out and requires spending time with it to understand how the mindless wonder of an author was thinking while assembling it.
 
#9 ·
Holy crap, there is two! Thank you.
I found it and I'm going to replace it as well.
Sorry for doubting you, that rear sensor in the diagram looked so close to the Crank sensor I just assumed they mislabeled it. (Not to mention 2 parts stores show that the car only needs 1)

Any ways, being that I haven't replaced them all at once what should I do now? Unplug them all turn the key on so the computer shows them all missing.
Then clear the codes, pull the battery, install the new one and then plug them all in before applying power?

Or simply clear all the codes, pull the battery, install the 3rd sensor, wait 10 minutes then start it?

Thanks again Brad, I really appreciate your responses.
 
#11 · (Edited)
I read your original post in haste, sorry, and have now taken the time to read it properly. At this point it has become glaringly apparent that you are going in the completely wrong direction on this issue. None of the sensors you are replacing have anything to do with a P0300 DTC. The service manual lists the following possibilities on page 9-252:

(K343) FUSED MAIN RELAY OUTPUT CIRCUIT
(K344) FUSED MAIN RELAY OUTPUT CIRCUIT
INJECTOR CONTROL CIRCUIT
COIL CONTROL CIRCUIT
IGNITION WIRE
SPARK PLUG
FUEL PUMP INLET STRAINER PLUGGED
FUEL SUPPLY LINE RESTRICTED
FUEL PRESSURE LEAK DOWN
FUEL INJECTOR
IGNITION COIL
FUEL PUMP MODULE
INTERNAL ENGINE COMPONENT
POWERTRAIN CONTROL MODULE (PCM)

If it only starts doing it over 2000rpm; with the miles on the car, you likely are looking at a failing fuel pump, or possibly bad fuel injectors.
 
#13 ·
I just wanted to follow-up on what finally resolved the issue.
It was a plugged up catalytic converter.

This was going to cost approximately $400 to have replaced so I sold the car. It served me well and will hopefully continue to do the same for the next owner.
The cat replacement is possible to DIY but I don't own a lift or ramps so it would have been almost impossible to do.

I ended up buying a Chevy Tahoe which I am thoroughly enjoying.

The ODBII scanner is similar if not exactly the one listed below. Well worth $25
Click Here


I appreciate all the help from this forum and hope this thread may be able to help others in the future.
Happy Halloween!
 
#15 ·
Hi Guys!

I have the same problem....

I already replace:
- Spark Plugs
- Coils
- 2 Sensor (Cramshaft)
- 1 sensor (Cramshaft Position)

I feel the car runs very good, but CEL its make me crazy.
I think replace Catalitic Converter (thinking about EGR have a problem)

The other think is move the car to Dodge dealer to update the SW and check if works.

Any ideas?
 
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