Question about 2003 Chevrolet TrailBlazer

1 Answer

P0303 Error code on reader. Changed all spark

P0303 Error code on reader. Changed all spark plugs and reset code. Check Engine Light re-appeared and now goes on and off. Still seems to stumble and act like it wants to stall when stopped. What next? 2003 Trailblazer LT--4.2L straight 6

Posted by on


1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.

    Brigadier General:

    An expert that has over 10,000 points.

  • Master
  • 4,044 Answers

Most likely it is a faulty O2 Sensor that needs to be replaced. It would be best if you took the vehicle to one of the Auto Parts stores that will read the codes for free so you can pick up the part and any special tools needed to replace it. The O2 Sensor requires a special socket to replace it.

Posted on Jul 13, 2010


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

3 Answers

How can I get rid of code P0303 ?

replace the coil,it is misfiring

Mar 27, 2015 | 1996 Ford Explorer

2 Answers

2008 Cadillac CTS returning P0303 after replacing spark plug and coil pack

Error Code: P0303
Cylinder 3 - Misfire Detected
Possible Cause:
Wiring harness, igniter and fuel injector connectors.
Ignition system. (Spark plugs gaps)
Fuel injector No. 3.
Fuel pressure.
Running out of fuel.
EVAP canister purge valve.
Evaporative emission system.
Low compression, cylinder No.3. (check valve clearance and throttle plate for excessive wear)
Engine control module (ECM).

Feb 27, 2014 | 2008 Cadillac Cts

1 Answer

Terraza P0303 Code. What's most likely cause? Injector, spark plug, wires or any of the above?

Might be dirty injector or burned valve. Check the connector on the injector. If good, run a compression test on all cylinders. If compression is significantly lower on #3, the head will have to come off. If compression is good, pull up the injector rail with injectors and wiring attached. Watch the injectors spray as someone cranks the engine.

Sep 02, 2017 | 2005 Buick Terraza

1 Answer

Have a 2001 ford expedition with a 5.4 triton has a misfire in the number 3 cylinder i changed the spark plug and the coil pack on it confused on what it could be that keeps throwing these codes

Vehicles: Any vehicle with the above symptoms.

You have a bad spark plug wire on #3, or possibly a clogged/malfunctioning fuel injector on Cylinder #3. Or, less likely, some of the other possible culprits mentioned below (exhaust valve/O2 sensor/Catalytic converter/ECC).

I'm presuming the OBD-II DTC code from the Expedition's computer is P0303.
Always try resetting the code and see if it returns - your new spark plug and new coil pack may have fixed the problem, but if the P0303 code isn't reset, it'll remain stored,and the CEL (Check Engine Light) will remain lit.

If I were standing in front of the vehicle right now, the 1st thing I'd do is put my "mechanic's stethoscope" on the fuel injector with the motor running to verify correct operation. Why would I do this first? Its free, and informative. You'll hear both the explosion in the cylinder, and the "tic" sound of the fuel injector solenoid as the injector operates. Auscultate the properly functioning cylinders first, so you know what to listen for.

If all you have is a medical/Sprague-Rappaport stethoscope. remove the auscultation bell, and replace it with a 12-inch (36 cm) long wooden dowel or solid/hollow metal rod as a substitute. Sound will transmit just fine through the wood/metal. Prefer metal, if you have a choice.

Here's the "official" P0303 write-up:
P0303 Code - Cylinder #3 Misfire
Technical Description

Cylinder #3 Misfire Detected

A P0303 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #3.
Symptoms may include:

the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present


A code P0303 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer (ECC)

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. In other cases the problems were faulty fuel injectors.

Dec 07, 2011 | 2001 Ford Expedition

3 Answers

2001 ford taurus error code p0303

That is a cylinder misfire code have you had the plugs changed, could be a bad plug maybe bad coil, or injector how does it run

Jul 01, 2009 | 1999 Ford Taurus

2 Answers

Error code p0303 cylinder 3 misfire My 2002 Ford Escape was in a front-end collision requiring the replacement of the radiator and cooling lines, etc. When it came back from the body shop the check engine...

It is possible that the wire may have been damaged and is arcing. Check the wire, may also be the plug. If that doesnt solve the issue it could be the ignition coil.

Apr 06, 2009 | 2002 Ford Escape

Not finding what you are looking for?
2003 Chevrolet TrailBlazer Logo

630 people viewed this question

Ask a Question

Usually answered in minutes!

Top Chevrolet Experts


Level 3 Expert

83772 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22413 Answers

Ronny Bennett Sr.
Ronny Bennett Sr.

Level 3 Expert

6927 Answers

Are you a Chevrolet Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides