P0203 & P0303 when engine is warmed up

2002 Buick Regal GS, 166,000 miles, 3800 Supercharged

I am getting 2 codes
P0203 - Cylinder 3 injector circuit malfunction. Tells me Open Circuit on my reader
P0303 - Cylinder 3 misfire detected.
Check Engine light will Flash.

Started a day ago. Drive the car after its been sitting and its fine. Take the car out after its been sitting for an hour or less and its has a hell of a miss and I get those two error codes. Done it 3 times now. Check engine light goes off when it runs fine, blinks when I get the miss.

What should I look for? Should I just take it in?

You have an injector problem that is causing a misfire on cylinder #3. Given the code you need to check the wiring to the #3 injector. It could have a broken or burnt wire or it could just be a loose connector. Sometimes the pins in the injector get corroded and need cleaned. Try unplugging the injector and plugging it in again. Also pull the plug and see what it looks like. The plug may be damaged due to either too much or too little fuel. If it looks good when you take it out then the problem is purely an injector issue.

You have an injector problem that is causing a misfire on cylinder #3. Given the code you need to check the wiring to the #3 injector. It could have a broken or burnt wire or it could just be a loose connector. Sometimes the pins in the injector get corroded and need cleaned. Try unplugging the injector and plugging it in again. Also pull the plug and see what it looks like. The plug may be damaged due to either too much or too little fuel. If it looks good when you take it out then the problem is purely an injector issue.

Now which cylinder is cylinder #3? Where are the injectors located? If it needs to be replaced, can I replace just the one injector, or should they all be replaced?

What size engine do you have and if it is a 3.8 is it supercharged or normally aspirated?

What size engine do you have and if it is a 3.8 is it supercharged or normally aspirated?

It is the 3800 Supercharged

Number 3 is the front middle cylinder so it is easy to get to. You can replace one injector at a time as they all may not be bad. To replace an injector you will need to bleed the fuel system. You can do this by pulling the fuel pump fuse located in the power control center under the hood. Once you bleed the fuel system unbolt the fuel rail that goes over the supercharger. Pull the injector wire and then disconnect the rail from the injectors. The injector should pull out of the head. Replace with a new one just make sure to coat the o-rings with vasoline so that they slip on easily without tearing. Reconnect fuel rail and wiring and start the vehicle.

Before replacing the injector check the wiring using a noid light. They can be purchased for a few dollars at Autozone or you could rent one. This will tell you if the pulse is getting to the injector. If it is then the injector is the issue. If not you will need to look at the wiring. It could be as simple as a bad connector or broken wire.

Number 3 is the front middle cylinder so it is easy to get to. You can replace one injector at a time as they all may not be bad. To replace an injector you will need to bleed the fuel system. You can do this by pulling the fuel pump fuse located in the power control center under the hood. Once you bleed the fuel system unbolt the fuel rail that goes over the supercharger. Pull the injector wire and then disconnect the rail from the injectors. The injector should pull out of the head. Replace with a new one just make sure to coat the o-rings with vasoline so that they slip on easily without tearing. Reconnect fuel rail and wiring and start the vehicle.

Before replacing the injector check the wiring using a noid light. They can be purchased for a few dollars at Autozone or you could rent one. This will tell you if the pulse is getting to the injector. If it is then the injector is the issue. If not you will need to look at the wiring. It could be as simple as a bad connector or broken wire.

Can unplug/replug/check for corrosion on the wiring connector without bleeding the system and removing the fuel rail?

Yes! The connector is for electrical operation only and has nothing to do with the fuel. You can unplug it while the engine is running if you wish. If you pull it out and check it you may want to put a little dielectric grease on the connectors to keep any water out of it. This will also make the connection less prone to corrosion.

If you don't have a noid light but do have a 194 peanut bulb around, you can plug the 2 wires from the bulb into the injector connector and see if it blinks while the car is running. Unfold the wires from the bulb so they stick out and squeeze the loops shut to make them stiff enough to plug into the connector. If it blinks the injector is faulty or the connection is bad/intermittent. If it stays on solid, the control circuit (pnk/blk wire) is shorted or the PCM is faulty. If it does nothing, check power at the voltage supply (solid pink wire) to a known good ground with the key on. If voltage is good then the control circuit is open or the PCM is faulty. You can also measure the resistance of the injector while it is unplugged and compare the reading to a known good injector or two to see if it is out of range. Same with the light test. Try it on a good injector circuit so you will be familiar with what a working circuit looks like while being tested.

If you don't have a noid light but do have a 194 peanut bulb around, you can plug the 2 wires from the bulb into the injector connector and see if it blinks while the car is running. Unfold the wires from the bulb so they stick out and squeeze the loops shut to make them stiff enough to plug into the connector. If it blinks the injector is faulty or the connection is bad/intermittent. If it stays on solid, the control circuit (pnk/blk wire) is shorted or the PCM is faulty. If it does nothing, check power at the voltage supply (solid pink wire) to a known good ground with the key on. If voltage is good then the control circuit is open or the PCM is faulty. You can also measure the resistance of the injector while it is unplugged and compare the reading to a known good injector or two to see if it is out of range. Same with the light test. Try it on a good injector circuit so you will be familiar with what a working circuit looks like while being tested.

Just for an update.

I looked at the injector wiring and it all looked good. I looked at replacing it myself and it was one of those "Maybe I can do it" moments. So I dropped it off by a shop by my work and they told me that the Number 3 Injector was shot, it was putting out low/intermittent voltage. They said they could change it out next week for 440$. I said I only want to change the 1 injector, he said that was all he was planning on. Needless to say, I think they were trying to take advantage of me. Shame on them.

I just bought/ordered all the parts needed, a new injector and an o-ring kit for 55$. My brother is going to help me put it in this weekend, say he can probably do it in under an hour, 2 at the most. I'll let you know how it goes.

$440 to change one injector is nuts. You did the right thing by ordering the parts yourself. I suggest that you purchase a repair manual for the Regal because it will assist you in doing the job.

That is high! The labor to replace one injector is 0.6 hour on your car. $60 if their labor rate is $100 per hour. Even if they charged a 1 hour diagnostic fee, that would leave the injector costing $280! (less taxes, etc) Take your time, lube the o-rings and you should have no problems. And remember to carefully de-pressurize the fuel lines first!

Brother helped me over the weekend to do it. Could not have been any easier.
This is what we did


Remove the Engine shroud
Remove the 3 bolts that hold the fuel rail and the one bolt that holds the fuel lines on top of the motor
Gently lift the fuel rail up slightly, and remove the three injectors
Replace the bad injector and re-o-ring the two other injectors
Lube and reinsert injectors
Bolt back together


Probably did it in less than hour, and that included alot of goof off time.
Thanks for the help guys!