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Has a po303 and a po300 code - 1997 BMW Z3 Roadster

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P0300 is a random misfire and P0303 is a misfire on cylinder 3. That's where the trouble is. Change your sparkplugs and see if the coil that drives the #3 cylinder has signs of damage. Then reset the code. If it comes back, swap that coil with another, reset the code, and see if the misfire code moves. If it does, the problem is the coil. If it does not, the problem is the plug, wire (if applicable), or ignition driver for the coil.

Posted on Nov 18, 2009


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Posted on Jan 02, 2017

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SOURCE: 1999 vw jetta 2.0

Sounds like two problems. P0300 and P0303 are possibly spark plugs. They could be a coil pack but I'm leaning toward a spark plug problem because of the other two codes - they're indicating O2 sensor problems. If the O2 sensors are screwed up, the car reverts to preprogrammed, rich fuel maps that send excessive fuel through the engine. The reasoning is, if the ECU can't trust the O2 sensors to determine how much fuel to burn optimally, it'll pump a bunch of extra fuel through the engine to keep it safe. Having too little fuel (aka running lean) can destroy an engine, so the ECU plays it safe and runs rich (too much fuel) instead. The consequences of rich running are relatively minor compared to lean running, but can and do tend to create excessive carbon buildup on the catalytic converter and O2 sensors, as well as fouling spark plugs.

First thing to do though is to swap the wires on your coil packs and see if you end up with a misfire code for the same cylinder #3. If you do, then it's the plug or wire. If it moves, it's the coilpack. Replace whichever part is faulty. You'll probably need oxygen sensors too, before you can clear all the codes.

Posted on Sep 02, 2008

  • 407 Answers

SOURCE: i got coes po604, po303, po300, and po301 for my

miss fire codes need to check tune-up, proper spark at all cylinders

Posted on Oct 15, 2009

  • 5370 Answers

SOURCE: My cadillac cts 2003 has

P0036 - Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 2.

The O2 will not cause a miss, but the miss can cause an O2 code. The O2 heater code you are getting is most likely just a bad O2, or possibly a bad fuse or even corrosion on the fuse terminals.


P0147 Heated Oxygen Sensor (HO2S) Heater Performance Bank 1 Sensor 3

I believe that this is the oxygen sensor at the rear of the catalytic converter. It's not the sensor itself, it's the heater circuit, which just needs power, although it can be set if the sensor itself isn't working instead of the "right" one, P0146 or another HO2S performance code. The heater circuits are just power and won't cause the sensors to interact.


PO300 P0301 PO303 PO305 is random misfire codes. Cylinder number 1,3 and 5 needs to be checked.


P2107- Throttle Actuator Control Module Internal Circuit.


For more help click this link directly:----


This should help.Keep updated.Thanks.Helpmech.

Posted on Feb 23, 2011

  • 236 Answers

SOURCE: kia optima-2004-2.4-po300,po302,po303,po320

Ignition failure sensor circuit problem. Either a bad sensor or connection.

Posted on Jun 06, 2011

  • 115 Answers

SOURCE: reads codes of po300,po302,po303,po305

Hi these are mis-fire codes ,
P0300 is a general mis-fire detected code the others relate to specific cylinders,
P0302 is cylinder 2 misfire
I would check your spark plugs first if Ok you need to make sure the coils are working ok for this you need an osciloscope to check output voltage if your not sure then take to a qualified mechanic with Cadilac experience it could be caused by an air leak,bad ECT sensor or even Mass air flow sensor ,codes only tell you the result not the cause

Posted on Jul 24, 2009

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I'm trying to find out what po303 and po300 means

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Escalade P0300 code 3cylinder

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If your throwing parts at it ---verse---getting it properly
diagnosed-- then put a new coil in cylinder # 3 (PO303)

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Bad coil pack, fouled plugs, bad sparkplug wires

there is a lot issue with this motor with the po300,po303 ,po304 . it has the do with the head and valves. you need to found out which cylinder is mis firing

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