Searching for additional causes for P3000: multiple misfires

Troubleshooting includes:
-new wires/plugs
-tested ignition coil with my 2008
-replaced cam sensor

Still showing P3000. Shop quoted $2000 to replace PCM.

If so, any recommendations on ordering refurbished/pre-programmed PCM’s online? Installation?

Thanks!

 

Here you go:P0300-P0306 CYLINDER MISFIRE




When Monitored:

Any time the engine is running, and the adaptive numerator has been successfully updated.

Set Condition:

The threshold to set the fault is application specific; it is tied to the level of misfire that will cause emissions to increase to 1.5 times the standard or in some cases 1%. It is always a two trip fault above the calibrated RPM. It takes 1 soft fail to set a malfunction and two trips to set the MIL. Three good trips to turn off the MIL.




Possible Causes




ASD OUTPUT CIRCUIT

INJECTOR CONTROL CIRCUIT

IGNITION WIRE

SPARK PLUG

IGNITION COIL

FUEL PUMP INLET STRAINER PLUGGED

RESTRICTED FUEL SUPPLY LINE

FUEL PUMP MODULE

FUEL PRESSURE LEAK DOWN

FUEL INJECTOR

ENGINE MECHANICAL

POWERTRAIN CONTROL MODULE (PCM)




VISUAL INSPECTION




NOTE: Anything that affects the speed of the crankshaft can cause a misfire DTC.










NOTE: When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit.







Turn the ignition off.

- Visually inspect the engine for any of the following conditions.

- Worn serpentine belt

- Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.

- Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys

- Corroded PCM power and ground circuits.

- Improper CKP, CMP, MAP, and TP Sensor mounting

- Poor connector/terminal to component connection. i.e., CKP sensor, Fuel Injector, Ignition coil, etc.

- Vacuum leaks

- Restricted Air Induction system or Exhaust system.

- Internal engine component failures.







SPARK PLUG

Turn the ignition off.

Remove the Spark Plug.

Inspect the Spark Plug for the following conditions.

- Cracks

- Carbon Tracking

- Foreign Material

- Gap size out of specifications

- Loose or broken electrode

NOTE: Lightly tap the bottom of the spark plug on a solid surface. The electrode in the spark plug should not move.




ENGINE MECHANICAL

Check for any of the following conditions/mechanical problems.

ENGINE VACUUM - must be at least 13 inches in neutral

ENGINE VALVE TIMING - must be within specifications

ENGINE COMPRESSION - must be within specifications

ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.

ENGINE PCV SYSTEM - must flow freely

TORQUE CONVERTER STALL SPEED - must be within specifications

POWER BRAKE BOOSTER - no internal vacuum leaks

FUEL - must be free of contamination

CAM LOBES - must not be worn excessively

CYLINDER LEAKAGE TEST - must be within specifications

VALVE SPRINGS - cannot be weak or broken




POWERTRAIN CONTROL MODULE (PCM)

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensor, Coil, Injector, and the Powertrain Control Module (PCM).

Look for any chafed, pierced, pinched, or partially broken wires.

Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensors, Coils, Injectors, and the Powertrain Control Module connectors.

Refer to any Technical Service Bulletins that may apply.

 

PCMs usually don't fail unless some sort of heat source or volatage surge/spike has affected it. They can be reset using factory WiTech software which a lot of shops have in the USA. Ron has a good knowledge of electrical things and codes so would suggest you go back to your shop and see what they think about his ideas.

 

i just replaced mine:
symptoms were: would run perfect for 20 seconds, then give a 0300 code and run rough. went through it ALL. plugs, coils, fuel, battery, crank sensors...the list went on. was soooo frustrating!!
mine was caused by a low power brownout (was being shipped overseas and the low battery on startup caused a brownout). they tried to reset to factory using the software...didnt work.
i got my replacement from wranglerfix its pricey, so i would make sure thats what it is first.
2k is WAY too much. the replacement PCM is 750-ish and its 3 bolts and 2 plugs.

i agree with sixty4x4...they commonly dont fail. and, be careful...a lot of times the reason they DO fail is due to a short in something...plugging in a new one will fail since the original issue didnt get fixed.
i would also ask: are you getting any actual symptoms other than the light? is the light flashing or just constant?
ron gave you a great list...i strongly suggest you start going down it before you throw a ~1k part at it

 

Thank you for the responses!

Any chance this issue could be related to a rebuild I had done 1500 miles ago? I spun a bearing and had it rebuilt.

The troubleshooting steps suggested is way beyond my experience level. I took it back to the shop where I had it rebuilt and they went thru a list of troubleshooters that pointed to the PCM, however it was not as thorough as the one outlined by Jedi.

I just can’t imagine spending another 2 grand for a PCM replacement and was just going to order a refurbished/pre-programmed one but now not so sure since I can’t say for sure if the underlying cause hasn’t been addressed.

 

Rock Auto sell refurbished PCMs for auto at $925 and for manual at $462

 

i guess i would ask: what did the shop do that points you to a PCM? did they do a simple compression test...leak down test?
it truly might BE a pcm, just asking if you have an idea on what they did/checked...