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Discussion Starter #1
on the way to work my engine light came on, managed to pull the codes and i'm getting P0308, can't seem to find any mention of it on this forum but a border search came up with engine miss fire on cylinder 8, does feel like its misfiring how do i clear the code or will it just go away.

anything to worry about ?

thanks
 

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P0308-CYLINDER 8 MISFIRE

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The misfire detection monitor software strategy in the Powertrain Control Module (PCM) is designed to detect an engine misfire. The PCM uses the Crankshaft (CKP) and Camshaft (CMP) sensors to determine when an engine misfire event is occurring and determine individual misfire events by monitoring the crankshaft rotational speed. A misfire is nothing more than a lack of combustion, which can be caused by poor fuel quality or metering, low compression, lack of spark or unmetered air entering the engine. On engines equipped with Exhaust Gas Recirculation (EGR), another possible cause is unwanted EGR flow. In the case of multiple cylinders misfiring or the PCM not determining the specific cylinder misfiring, P0300 Multiple Cylinder Misfire will set.





  • When Monitored: Any time the engine is running and the adaptive numerator has been successfully updated.
  • Set Condition: If the Powertrain Control Module (PCM) detects that the variation in crankshaft speed between each cylinder exceeds a calibrated value, based on engine RPM and load, a fault is set.
Possible Causes

FUEL DELIVERY SYSTEMIGNITION COIL, WIRING, OR CONNECTORSECT SENSOR, WIRING, OR CONNECTORSMAP SENSOR, WIRING, OR CONNECTORSO2 SENSOR, WIRING, OR CONNECTORSENGINE MECHANICAL SYSTEMPOWERTRAIN CONTROL MODULE (PCM)
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).



1.ACTIVE DTC 1.Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.2.Turn the ignition on.3.With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.4.Start the engine and allow it to reach operating temperature.
WARNING:When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in possible serious or fatal injury.



NOTE:Attempt to operate the vehicle under conditions similar to which the DTC was set.
NOTE:It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.5.With a scan tool, select View DTCs.

Is the status Active for this DTC?

Yes


  • Go To 2
No




2.DIAGNOSTIC INSPECTION

NOTE:Anything that affects the speed of the crankshaft can cause this DTC to set. When a misfire is detected, the PCM will shut down the injector control circuit for the misfiring cylinder. Misfire may occur and may not be caused by component failure. Any of the following conditions can cause a misfire.1.
Inspect the engine for any of the following conditions:



  • Worn serpentine belt
  • Misalignment or binding water pump, P/S pump or A/C compressor pulleys
  • Improper CKP, CMP, or MAP Sensor mounting.
  • Poor connector/terminal to component connection for CKP sensor, CMP sensor, MAP sensor, throttle body, fuel injector, ignition coil, etc.
  • Corroded PCM power or ground circuits.
  • Vacuum leaks.
  • Restriction in the air induction or exhaust system.
  • Internal engine component malfunction.
  • Moisture on ignition system components
  • Insufficient fuel
  • Low quality fuel
  • Manual transmission bog
  • Towing overload

Were any problems found?

Yes


No


  • Go To 3


3.CHECKING THE FUEL DELIVERY SYSTEM 1.Perform the diagnostic procedures for FUEL PRESSURE LEAK DOWN and FUEL DELIVERY SYSTEM OUTPUT - FLOW TEST. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 4


4.CHECKING THE IGNITION COIL OPERATION 1.Perform the diagnostic procedure for CHECKING THE IGNITION COIL OPERATION. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 5


5.CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION 1.Perform the diagnostic procedure for CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 6


6.CHECKING THE MAP SENSOR OPERATION 1.Perform the diagnostic procedure for CHECKING THE MAP SENSOR OPERATION. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 7


7.CHECKING THE OXYGEN SENSOR OPERATION 1.Perform the diagnostic procedure for CHECKING THE OXYGEN SENSOR OPERATION. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 8


8.CHECKING THE ENGINE MECHANICAL SYSTEM 1.Perform the diagnostic procedure for CHECKING THE ENGINE MECHANICAL SYSTEM. (Refer to 29 - Non-DTC Diagnostics/Drivability - Gas - Diagnosis and Testing) .

Were any problems found?

Yes


No


  • Go To 9


9.POWERTRAIN CONTROL MODULE (PCM) 1.Using the wiring diagram/schematic as a guide, inspect the wiring and connectors relative to the components tested in this procedure.2.Look for any chafed, pierced, pinched, or partially broken wires.3.Look for broken, bent, pushed out or corroded terminals.4.Monitor the scan tool data relative to the components tested in this procedure and wiggle test the wiring and connectors.5.Look for the data to change or for a DTC to set during the wiggle test.6.Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes


No


 

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Discussion Starter #3
wow thanks for the compressive response, now all i need to do is find someone in the uk to figure it out lol will the code clear if the problem doesn't persist ?
 

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wow thanks for the compressive response, now all i need to do is find someone in the uk to figure it out lol will the code clear if the problem doesn't persist ?
Yes, the code "should" self clear after a couple of "drive cycles" without the problem returning. Or just have it cleared.

However you state it does feel like its "miss-firing" so that indicates a problem.

Also I might have missed it but year of vehicle can help narrow down a concern... ;)
 

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the first thing i would do is swap the plugs with the adjacent cylinder, see if it repeats, if the problem persist i would swap the injector and repeat the process
Luke
 

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Discussion Starter #8
thanks guys

its a 09 RT, it would be so difficult to run a car like this in the UK if it wasn't for these forums

i miss typed i meant to say to doesn't feel like its misfirring

i pulled the battery lead today and so far it hasn't returned,

thanks again

kev
 

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P0308

Hi
Steve's process of moving parts around is a good way of isolating the cause. Start with plug and or coil first

I've seen a coil cause this on this year car
 

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HI Guys,

I have a 2014 RT.

I took it for a smog test this morning, passed with flying colors.

10 miles (or less later) I have a check engine light with two codes appearing:

- P0300 - multiple mis-fire
- P0308 - Cyl 8 mis-fire

Have any of you ever heard of the check engine light and these codes appearing after a smog test?

Could it potentially be a loose sensor from the smog test itself perhaps?

Should I just take it into my local mech and have them troubleshoot it or should I give it a little driving time to see if it works itself out?

Thanks in advance
 

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Welcome to the forum. You could try resetting the adaptives by pulling fuse #2 and see if the code pops back up again. BTW there was a TSB for P0300 but it applied to the 6.4L which reflashed the PCM. Doubt the emission read had anything to do with it. As for loose sensors, usually the camshaft/crankshaft position sensors are used by the PCM to trigger spark sequences and if they where flaky you would get a code for them as well as the misfires. If the misfire comes back or is persistent it could be bad plug(s), coil(s), loose intake manifold, bad injector or worst case...issue with cam/lifters (have read about a couple of guys with 6.1L motors having misfire issues which was do to worn lobe). See the P0300 pdf which was pulled from the online chiltons manual for more possible causes and diagnostics.
 

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2020 Dodge Challenger Hellraisin Scat Pack
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HI Guys,

I have a 2014 RT.

I took it for a smog test this morning, passed with flying colors.

10 miles (or less later) I have a check engine light with two codes appearing:

- P0300 - multiple mis-fire
- P0308 - Cyl 8 mis-fire

Have any of you ever heard of the check engine light and these codes appearing after a smog test?

Could it potentially be a loose sensor from the smog test itself perhaps?

Should I just take it into my local mech and have them troubleshoot it or should I give it a little driving time to see if it works itself out?

Thanks in advance

Do not know where you are and what is involved in a smog test. The ones I have had done here in CA do not involve the tech really touching the engine or any part of the car other than opening the engine compartment lid and in the past positioning the car on a set of rollers and inserting an exhaust sniffer in the tail pipe then running the engine in gear with the rear tires on the rollers at IIRC 1500 RPMs then 2500 RPMs.

Or more recently just connecting a special computer to the car's OBD2 port and then while the engine idles let the computer query the car for what is necessary to confirm (or not) the car is in compliance.

If the process is different where you are, if the tech say makes some checks he could have (?) caused a coil to plug connection to become loose. If you are comfortable checking for a loose plug/coil connection at the # 8 spark plug/coil for a loose connection, and to be thorough doing the same for all the spark plug/coil connections then do so.

Otherwise you will have to take the car in.

'course, what often is the case the tech would read the code then clear it and either test drive the car or have you test drive the car -- just use it normally -- and see if the CEL came back on and with the same error code.
 

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Hey guys,

So took the car in, mechanics ran a software update (per a dodge service bulletin) and a reflash.

I drove the car for almost exactly a week (around 10 miles a day) and the engine light is back on.

This time I’m only getting the P0300

(last time I had P0300 and P0308)

So it looks like P0308 has cleared but I’m still having to deal with the 300 (multi miss fire).

Booked it back in for Monday, the mechanics will then start the process to diagnose.

With a P0300, i know it’s super vague, so can any of the experienced guys here educate me on what you would check and in what order so I at least understand the process?

Is the P0308 likely to return after a little more driving?
 

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2015 RT 5.7 M6
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Hey guys,

So took the car in, mechanics ran a software update (per a dodge service bulletin) and a reflash.

I drove the car for almost exactly a week (around 10 miles a day) and the engine light is back on.

This time I’m only getting the P0300

(last time I had P0300 and P0308)

So it looks like P0308 has cleared but I’m still having to deal with the 300 (multi miss fire).

Booked it back in for Monday, the mechanics will then start the process to diagnose.

With a P0300, i know it’s super vague, so can any of the experienced guys here educate me on what you would check and in what order so I at least understand the process?

Is the P0308 likely to return after a little more driving?
Did you even look at the PDF I posted earlier regarding P0300. There are diagnostic steps in it. I don't think you are going to find someone with the answer right out of the box (just take a look at some posts from other members with misfire codes) as it could be one (or more) of several things wrong.

 
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