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GM excessive fuel trims after calibrating MAF and SD

Practical Reflash Tuning

Discussion and questions related to the course Reflashing

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Hey guys I've noticed after recalibrating the MAF and SD systems I get quite a decent negative short term trim. While I am calibrating them separately I get it quite close to zero error. However once I revert to blended and re-enable the short term trims the trims climb quite negative. I'm wondering if it's the lambda meter I'm using as an analogue input to the HP tuners dongle. While I know there is an inherent offset error with the analogue inputs I doesn't seem to be a consistent problem. The open loop part of the tune seems to be reasonably accurate. The more I think about it, the more I think it could be due to the analogue input offset problem you mentioned Andre. Has anyone used the serial input that was mentioned? How does it work and does it give a good result? I feel like after a 3 hour tuning effort I'm not getting the perfect result I should be. Many thanks in advance guys.