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P0170 OBD2 Fault on 2001 Vauxhall Corsa: MAF Sensor Replacement Caused Driving Issues - Fix and Lessons Learned

Model: UNKNOWN Fault Code: P0170 Posted: 2007-09-07 11:39

Hello, I own a 2001 Vauxhall Corsa and recently encountered a persistent OBD2 fault code P0170, indicating an issue with the fuel trim system. The check engine light (MIL) activated unexpectedly, though the car otherwise drove smoothly. Using a scan tool, I confirmed the presence of P0170, which showed a fuel trim value consistently at +25%. After multiple attempts to clear the code, it returned each time. I then took the vehicle to the official Vauxhall dealership for diagnosis. They identified a faulty Mass Airflow (MAF) sensor as the root cause and recommended replacement. I agreed and purchased a new MAF sensor from an eBay seller who claims to have sold many units with positive customer feedback. After installation, the car struggled to start and once it did, it exhibited a severe 'flat spot' during acceleration—so pronounced that I nearly clipped the windscreen when pulling out at junctions. After a 20–30 mile drive, the issue persisted without improvement. Interestingly, the MIL remained off, and post-replacement fuel trim readings stabilized around +2.5%. However, due to the dangerous driving behavior, I reverted to the original MAF sensor before any further damage occurred. With the old sensor reinstalled, the car drives perfectly again—though the MIL is now back on. I'm at a loss as to what went wrong and why the new MAF sensor caused such severe performance issues. The P0170 code was not present during the original diagnosis or after reinstallation of the original sensor. Could this be related to incorrect part compatibility, poor quality control, or faulty calibration? I'm seeking advice on how to proceed safely and effectively. Thanks for any insights—Neill

Related fault codes
P0170
Comments (4)
Anonymous 2007-09-07 12:09

I’m not familiar with Vauxhall models specifically, but it’s important to ensure you’re using the correct Mass Airflow Sensor (MAF) for your 2001 Corsa. P0170 typically indicates a fuel trim imbalance—this code is relatively rare and may point to sensor inaccuracies or wiring issues. I’d recommend verifying with an authorized dealership before replacing parts.

Anonymous 2007-09-07 12:47

The dealership diagnosed a faulty MAF, but after installing an eBay-sourced MAF, the car became dangerously unstable—especially during acceleration. Why not simply purchase the original OEM MAF from the dealer instead? The price difference was £280 (including fitting) versus £45 on eBay. It seems like the eBay unit may be substandard or even a factory reject. Was there any quality assurance process in place for these parts?

Anonymous 2007-09-08 00:39

Thanks for your response. The price difference was significant: £280 from the dealer (including labor, which takes only two minutes), compared to £45 on eBay. I acknowledged the risk but believed the potential savings outweighed the risks initially. I contacted the eBay seller who apologized and confirmed that their MAF sensor appears to be defective—having sent a replacement immediately. It’s possible some eBay parts originate from factory reject batches, which may fall outside acceptable quality thresholds during production testing. These units might pass basic checks but fail under real-world conditions. If the second unit performs similarly, I will likely request a full refund and switch to the official Vauxhall OEM part. I’ll update this thread once the next sensor is installed. Thanks for your input—Neill

Anonymous 2008-04-25 07:00

Sorry for not updating earlier—I only remembered when someone asked about my final outcome. The eBay seller sent a second MAF sensor, but it performed identically to the first—one with severe flat spot and no improvement in drivability. Fortunately, they issued a full refund. I then purchased the official Vauxhall OEM MAF sensor. Since installation, the car has run smoothly and reliably—no more P0170 or driving instability. This experience highlights the risks of using non-OEM parts from unverified sources, especially on critical sensors like the MAF. I hope this helps others avoid similar issues. Thanks for reading!