2003 Gmc Sierra Error Code P0300 And P1075?

c0d39177 · February 13, 2009

Recently, my truck would seem to crank, and never really seem to "fire up" like it used to, it would just start to kind of sputter, and then finally run. This predominately happens when the engine is warm, or has been turned off for a short period of time. When the truck is cold, it seems ti fir up normally. I have also noticed that my idle is rough, especially at stop signs. I ran the codes once the check engine light appeared, and received a P0300 and P1075. Respectively, Random Misfire, and System Too Rich Bank 2. I am looking for a little help in diagnosing this further. I have heard that this may be the O2 sensor, but would like some input from members here who may have experienced similat problems. Thanks for the help.

C6Racer · February 15, 2009

A bad O2 sensor would be the most logical explanation. I would also check to make sure that the right side air injection system check valve isn't stuck closed. A stuck closed valve would prevent the injection of O2 into the exhaust causing the sensor to read rich. You might also want to make sure the coolant temp sensor is properly plugged in. If those check out ok, I would condemn the O2 sensor.

c0d39177 · February 16, 2009

A bad O2 sensor would be the most logical explanation. I would also check to make sure that the right side air injection system check valve isn't stuck closed. A stuck closed valve would prevent the injection of O2 into the exhaust causing the sensor to read rich. You might also want to make sure the coolant temp sensor is properly plugged in. If those check out ok, I would condemn the O2 sensor.

Thanks for the possible solutions! To troubleshoot, where exactly might I locate the right side air injection system check valve to check? As well, where can I locate the coolant temp sensor to ensure it is properly seated? Again, thanks for the suggestions. If it does turn out to be the O2 sensor, which one should I replace, the first or second, or both?

C6Racer · February 17, 2009

Well, your truck may, or may not, have an air injection system. There is one tube bolted onto each exhaust manifold if you do have it. The check valve is a piece that has a rubber hose clamped to it and is threaded onto the tube that bolts to the exhaust manifold. It will let air into the manifold, but not out.

As for the coolant temp sensor, I'm not sure what engine you have, but on the 5.3L it's located at the front of the driver's side cylinder head right next to the front spark plug boot. Make sure it's plugged in properly.

As for the O2 sensor, you should have four of them. You will need to replace the one before the catalytic converter on the passenger's side, if that turns out to be the problem.

Just FYI, Bank 1 is the driver's side(left) and Bank 2 is the passenger's side(right).

Good luck.

c0d39177 · February 17, 2009

Thanks for the great info. as its greatly appreciated. I will hopefully be tackling this project this weekend, and will update as soon as I get it fixed. Thanks.

c0d39177 · March 3, 2009

Well I finally got around to trying to fix this issue. I did double check the coolant temp sensor located by the first spark plug on the drivers side, only to find it was properly seated. The air injection system I could not locate on my 2003 5.3L engine. I then moved on to the O2 sensor. I replaced the sensor on the passengers side before the cat. Unfortunately I still have all of the same issues. Any thoughts as to what it might be now? Thanks.

C6Racer · March 3, 2009

This is an extremely confusing issue. At first I thought "maybe it's a leaky fuel injector since it's just in bank 2", but what threw me off completely is the P0300 code. "If it's a random misfire, then how would it only detect a rich condition on one side of the engine?", I thought to myself. Another thing that led me to believe it was a bad O2 sensor is the fact that your engine starts up just fine when it's cold because the computer ignores the O2 sensors at those times anyway. When it's warm is when the computer uses their signals to determine the fuel mixture. I'm very sorry I misled you. I thought about my answer for a very long time before I even began typing. I was absolutely certain I ruled out a bad fuel injector or spark plugs.

What spark plugs do you have? GM engines seem to hate any spark plug that isn't AC Delco or copper. Also, do you have the means to perform a fuel injector balance test? It requires the use of a fuel pressure gauge and a balance tester, which is something that is plugged into one injector at a time to energize it for a second.

Anyway, I've tried to use Bosch Platinum plugs and aftermarket iridium's, but they only made my engine run like crap. I'm currently running coppers and it runs much smoother.

Good luck!

c0d39177 · March 4, 2009

This is an extremely confusing issue. At first I thought "maybe it's a leaky fuel injector since it's just in bank 2", but what threw me off completely is the P0300 code. "If it's a random misfire, then how would it only detect a rich condition on one side of the engine?", I thought to myself. Another thing that led me to believe it was a bad O2 sensor is the fact that your engine starts up just fine when it's cold because the computer ignores the O2 sensors at those times anyway. When it's warm is when the computer uses their signals to determine the fuel mixture. I'm very sorry I misled you. I thought about my answer for a very long time before I even began typing. I was absolutely certain I ruled out a bad fuel injector or spark plugs.
What spark plugs do you have? GM engines seem to hate any spark plug that isn't AC Delco or copper. Also, do you have the means to perform a fuel injector balance test? It requires the use of a fuel pressure gauge and a balance tester, which is something that is plugged into one injector at a time to energize it for a second.

Anyway, I've tried to use Bosch Platinum plugs and aftermarket iridium's, but they only made my engine run like crap. I'm currently running coppers and it runs much smoother.

Good luck!

OK, so after replacing the O2 sensor pre-cat on the passengers side of the engine, I still had the above mentioned problem. I proceeded to clear the codes to see what reported back. Once cleared it only took a couple of hours to activate the check engine light. Once I ran the codes I received one P0300 and TWO P1075 codes indicating a rich condition bank 2. The rep. at the local auto store had me check my air filer since it is an aftermarket, but I found no issues there. He also mentioned I might want to replace the plugs and wires. I have 55k on the truck and the plugs and wires are original. Any thoughts? Thanks.

c0d39177 · March 8, 2009

Since the O2 sensor failed to fix the problem, I moved on to replacing the plugs on the truck. Unfortunately, no difference. I replaced the plugs with brand new AC Delco Iridium plugs, but checked the wires, and did not replace them. I have now changed the O2 sensor on the passengers side, completely changed the plugs, and even checked the air intake system and MAF for any damage or dirt since I use an aftermarket air intake system. I hae not reset my check engine light yet, but can almost gaurenteee I will be receiving my same codes, as nothing I have done has solved the issue. I am know wondeering if I might turn my attention to the fuel system? Possibly the injectors, filters, sending unit etc. Any help or guidence moving forward is appreciated. Thanks.

Stevens03 · March 8, 2009

Have you cleaned your MAF sensor? It's a common problem that causes P0300 issues.

Its certainly an easy thing to do.

Steven

62handler · March 8, 2009

Leaky fuel pressure regulator.

see it all the time on these engines, the regualtor is acually leaking into the vaccume hose atached to it, causes the long crank on a short hot soak, kinda feels like its lean when its starting up but its acually rich. also why it fires up just fine cold, the little bit of extra fuel isnt hurting anything when its cold.

next time you go out to your truck pull the vaccume hose of the regulator and the inside of the hose will be wet, by how bad yours sounds a little fuel might even spill out when you do it.

verry simple to replace, theres either a big clip over the regulator (you'll know it if you have it) or theres an internal snapring holding the regulator into the fuel rail. just remove wichever one you have, pull the regulator out, make sure that theres no o-rings left in the housing, slide the new one into place and replace the snap ring or clip and your done.

there shouldnt be too much residual pressure in the fuel rail if it is leaking but just to be safe i ussually pull the fuel pump relay out and crank the engine to bleed off pressure, it migh even fore up yet, just let it run untill it dies and you should be good to go.

hope this helps

ryan

c0d39177 · March 8, 2009

Leaky fuel pressure regulator.

see it all the time on these engines, the regualtor is acually leaking into the vaccume hose atached to it, causes the long crank on a short hot soak, kinda feels like its lean when its starting up but its acually rich. also why it fires up just fine cold, the little bit of extra fuel isnt hurting anything when its cold.

next time you go out to your truck pull the vaccume hose of the regulator and the inside of the hose will be wet, by how bad yours sounds a little fuel might even spill out when you do it.

verry simple to replace, theres either a big clip over the regulator (you'll know it if you have it) or theres an internal snapring holding the regulator into the fuel rail. just remove wichever one you have, pull the regulator out, make sure that theres no o-rings left in the housing, slide the new one into place and replace the snap ring or clip and your done.

there shouldnt be too much residual pressure in the fuel rail if it is leaking but just to be safe i ussually pull the fuel pump relay out and crank the engine to bleed off pressure, it migh even fore up yet, just let it run untill it dies and you should be good to go.

hope this helps

ryan

OK, so I went to check the FPR on the truck after arriving home and letting the truck sit for about 1 hour. The FPR on my engine is a small silver cylinder with a small vacuum line coming off from the top. I removed the hose, and the inside appeared faily dry, I thhink. However, while looking into the hose, I heard a small hissing sound coming from the FPR itself. Afer about 30 seconds, gas started to run out of the FPR. Is this normal? Should I replace the FPR just to be sure? Thanks for all of the feedback and help.

PS - I have already checked the MAF and found it to be clean and free of any restrictions or visible damage.

superjim · March 9, 2009

Gas should "NOT" run out of the FPR at the vacuum port...at all.

If it is running out at the vacuum port...replace the FPR.

62handler · March 9, 2009

there is your problem. replace that and you should be good to go.

c0d39177 · March 9, 2009

Thanks everyone for the feedback. Looks like I'll be grabbing a new FPR tomorrow and replacing the current one on my GMC. I'll post back with the results ASAP. Thanks again.