Kassan1973 Posted July 3, 2020 Report Share Posted July 3, 2020 Hello i have a G4 ecu which was working fine on a delco 3 bar map sensor , i at one stage broke off the vacuum line fitting on sensor and glued it back on before ordering a new sensor both chinese unis ! when i fitted the new sensor it would not calibrate =/- 5 kpa error but when plugged old one back in which had previously calibrated it again would not calibrate same error both sensors work fine and show zero vacuum in fuel map with engine off and also 1.55 volts , car is running fine but would there be any reason why both units would now not calibrate. Thanks Dean Quote Link to comment Share on other sites More sharing options...
Adamw Posted July 3, 2020 Report Share Posted July 3, 2020 With Key on, engine not running, open the runtimes screen (hit F12 key) and go to the analog tab. Tell us what the MAP and BAP parameters read. Quote Link to comment Share on other sites More sharing options...
Kassan1973 Posted July 5, 2020 Author Report Share Posted July 5, 2020 Hi Adam first pic is the latest sensor i purchased and second is original one i had which calibrated fine when first installed, i se a slight difference in voltage 1.64 Vs 1.65 maybe im missing something. details taken with engine cold sorry if i go for a drive a will get figures with engine hot . Thansk Quote Link to comment Share on other sites More sharing options...
Kassan1973 Posted July 9, 2020 Author Report Share Posted July 9, 2020 Any feedback on this Regards Dean Quote Link to comment Share on other sites More sharing options...
Adamw Posted July 9, 2020 Report Share Posted July 9, 2020 Sorry I missed your last reply. It appears to me that the BAP reading 100Kpa looks quite realistic assuming you live near or slightly above sea level. The displayed MAP value of 107Kpa for 1.64V is dead on GM's quoted curve so the ECU is interpreting that voltage correctly. However, the MAP sensor reading 107Kpa with the engine off would only be correct if you live ~500M below sea level, which there are not many places like that on earth. So I tend to believe the BAP is probably reading correct which would suggest both MAP sensors are reading wrong. I can give you a custom cal to fudge the MAP to make it match the BAP if you like but if they are already reading 7KPa/1psi out at atmospheric pressure do you really want to trust them at say 30psi? Quote Link to comment Share on other sites More sharing options...
Kassan1973 Posted July 9, 2020 Author Report Share Posted July 9, 2020 Thanks Adam i will purchase a better quality one locally and try to send the lastest one back for refund. Cheers Dean Quote Link to comment Share on other sites More sharing options...
Adamw Posted July 10, 2020 Report Share Posted July 10, 2020 If its not already too late, can you try the calibration below. Looking at it again this morning I found the GM ecu that those sensors are designed for use a 5.1V power supply, so many of the published calibrations ( and possibly the cal in the G4 are wrong when a sensor is powered by 5V). There are also two diffrent variations of formula given on the delphi data sheets which both give different results! So below is my best guess. Quote Link to comment Share on other sites More sharing options...
Kassan1973 Posted July 14, 2020 Author Report Share Posted July 14, 2020 Thanks i bought another one but ill keep this in mind strange thing is the original one i have did calibrate ok when first installed. Cheers Dean Quote Link to comment Share on other sites More sharing options...
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