What do these codes mean? PO 303 & PO 305

10

Asked by Jan 29, 2017 at 07:05 PM about the 2006 Lexus GS 300 AWD

Question type: Maintenance & Repair

A light came on on my dash. I took my car into my friend who owns his own shop and he came up with 2 codes - PO 303 & PO 305.

What do they mean?

3 Answers

73,765

P0303 LEXUS - Cylinder 3 Misfire Detected... Possible causes; Faulty spark plug 3, Clogged or faulty fuel injector 3, Faulty ignition coil 3, Fuel injector 3 harness is open or shorted, Fuel injector 3 circuit poor electrical connection, Ignition coil 3 harness is open or shorted, Ignition coil 3 circuit poor electrical connection, Insufficient cylinder 3 compression, Incorrect fuel pressure, Intake air leak......P0305 LEXUS - Cylinder 5 Misfire Detected.... Possible causes; Faulty spark plug 5, Clogged or faulty fuel injector 5, Faulty ignition coil 5, Fuel injector 5 harness is open or shorted, Fuel injector 5 circuit poor electrical connection, Ignition coil 5 harness is open or shorted, Ignition coil 5 circuit poor electrical connection, Insufficient cylinder 5 compression, Incorrect fuel pressure, Intake air leak.... The P0305 code means that the cylinder 5 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 5. If the problem persist more tests needs to be done to diagnose problem.

3 of 3 people found this helpful.
10

Thank you for your quick response. I appreciate your help.

1 of 1 people found this helpful.
70,255

If cylinders 3 and 5 are next to each other you may be looking at a blown head gasket. Check the compression on those two cylinders, if they are next to each other. If they're both very low or zero, it's a blown head gasket. HTH. -Jim

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