2005 Ion 2.2 Ecotec P0300 and P0171 HELP!
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Junior Member
Joined: Mar 2026
Posts: 5
I have been working on the same two issues on my '06 Coupe 3 for over a year and I think I may have the answer: the ECU needs to be reprogrammed to the latest soft/firmware. Here's why I have come to this conclusion - I have done a complete timing job, including R&R the head with new int/exh valves and valve oil seals and fuel injectors; new MAP, MAF, crank position sensors; and new ignition control module and coil packs. I was also chasing an EVAP problem - replaced both the purge and vent solenoids. I did a smoke test and found no leak under the hood. It turned out to be a problem with the gas cap seat, the part that the gas cap locks into, had broken loose from the filler neck. A liberal amount of epoxy fixed that and the EVAP small/large leak detected errors never came back. So, after all that, the random misfires and P0171 came back.
First of all, it is HIGHLY suggested you get a good OBDII scan tool that can read live data to see the misfire counts and the Long Term Fuel Trim. There are a few good instructional videos on YT on what the LTFT does. I recommend checking them out. According to Saturn service documentation, the 2.2 throws a P0171 when it detects the LTFT has reach 19%. Common causes for this is a vacuum leak after the air filter box. Any air not seen by the MAF will be seen by the oxygen sensor 1 (forward of the catalytic converter) which will see too much oxygen in the exhaust which in turn will trigger the ECU to add more fuel.
As you can see, I have addressed many - if not all - the 'known' remedies to correct P0300 and P0171. My last stab at this is to have my ECU updated with the latest software / firmware. Many online resources point to misfires and fuel trim problems can be fixed with the updated ECU. I'll update this thread once I get the ECU installed and had run the car through many run cycles to get stable readings to see if this worked or not.
Hope this helps and Good Luck!
First of all, it is HIGHLY suggested you get a good OBDII scan tool that can read live data to see the misfire counts and the Long Term Fuel Trim. There are a few good instructional videos on YT on what the LTFT does. I recommend checking them out. According to Saturn service documentation, the 2.2 throws a P0171 when it detects the LTFT has reach 19%. Common causes for this is a vacuum leak after the air filter box. Any air not seen by the MAF will be seen by the oxygen sensor 1 (forward of the catalytic converter) which will see too much oxygen in the exhaust which in turn will trigger the ECU to add more fuel.
As you can see, I have addressed many - if not all - the 'known' remedies to correct P0300 and P0171. My last stab at this is to have my ECU updated with the latest software / firmware. Many online resources point to misfires and fuel trim problems can be fixed with the updated ECU. I'll update this thread once I get the ECU installed and had run the car through many run cycles to get stable readings to see if this worked or not.
Hope this helps and Good Luck!
It?s showing out of spec on the fuel trim cell at 37 in red since it?s over 30. Not sure what this means.
I did finally find out it?s cylinder 3 misfiring even though all the spark plugs look the same.
this might sound silly but how could my ecu have got out of program? It?s been running 21 years with the same programming with no issues. Thanks.
Junior Member
Joined: Oct 2024
Posts: 6
From: Raleigh, NC
ECU UPDATE
The last I wrote was going to update you all on if an ECU updated to the latest firmware/software would help. I can say now that it has, at least for my Saturn. This has been my experience - yours my be different.
If you recall, I already addressed all the common causes for P0300 and P0171. The only thing left was the ECU. I contacted Flagship One. They sent me an updated used ECU that was plug-n-play. While it probably would have worked fine in my vehicle, I had to send it back because it didn't have my vehicle's VIN encoded. It had the donor car's VIN. This is a problem in my state where they use the OBDII port for state vehicle inspections. They took it back, no problem, and sent me another ECU with the correct VIN and vehicle type.
Three things I had to do to it once I received it:
I took the car out for a 150 mile drive. It ran great! I'll need to put more miles on it to be sure the prior problems don't come back.
The last I wrote was going to update you all on if an ECU updated to the latest firmware/software would help. I can say now that it has, at least for my Saturn. This has been my experience - yours my be different.
If you recall, I already addressed all the common causes for P0300 and P0171. The only thing left was the ECU. I contacted Flagship One. They sent me an updated used ECU that was plug-n-play. While it probably would have worked fine in my vehicle, I had to send it back because it didn't have my vehicle's VIN encoded. It had the donor car's VIN. This is a problem in my state where they use the OBDII port for state vehicle inspections. They took it back, no problem, and sent me another ECU with the correct VIN and vehicle type.
Three things I had to do to it once I received it:
- Perform the PASSLOCK ignition key learning procedure. They can send you this procedure or you can find it on the 'net
- Perform the Crankshaft Position Sensor Relearn procedure.
- Perform an Oil Reset procedure. (it was at 0% when reading it from the scanner. I bumped it to 80% since I recently changed the oil).
I took the car out for a 150 mile drive. It ran great! I'll need to put more miles on it to be sure the prior problems don't come back.
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Joined: Apr 2015
Posts: 3,229
From: Willamette Valley, Oregon
That sounds like you may have succeeded repairing your car. Thank you for the report. We appreciate when we hear about a final success. Hang around if you like, the more the merrier.
Thread Starter
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Junior Member
Joined: Mar 2026
Posts: 5
Getting there but not quite fixed fully.
Hey everyone. A little update. I got another coil pack and bam that has fixed my misfire. Can?t believe that one was already toast within 6 months.
Car is running so much better! Lean codes are gone and so are misfires.
I did get the check engine light last night when coming home. It?s showing code p0341 camshaft position sensor performance.
Anyone know how I should troubleshoot? I?m assuming it?s due to running the car for a week with lean and misfire codes?
Thanks!
Car is running so much better! Lean codes are gone and so are misfires.
I did get the check engine light last night when coming home. It?s showing code p0341 camshaft position sensor performance.
Anyone know how I should troubleshoot? I?m assuming it?s due to running the car for a week with lean and misfire codes?
Thanks!
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