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Don't change your wideband LSU 4.9 Plug

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Just creating a quick post because I learnt something new yesterday and it was an expensive mistake. On Saturday evening, I was working on my GTR and wiring a wideband sensor, a broke one of the connecters with a bad pin and I went searching for new pins. Instead of buying a new pin, I decided I convert the plug to a DTM style connector, however, I soon realised after cutting off the plug, quite close to the plug end that Bosch LSU 4.9 Sensor has a calibration resistor built into the connect and it's unique to each LSU 4.9 Sensor, and hence, you cannot cut of the plug, without using free air calibration instead (and then you just have a LSU 4.2). So now I am out 140 bucks for a new sensor and connector and I need to ensure I get the crimping correct otherwise I will need to buy another plug for the pins. I wanted to make this post so no one repeats my stupid mistake.

It's not uncommon for LSU 4.9 sensors to be re-terminated to an autosport connector.

The calibration resistor is only relevant on a new sensor, once it has been in use an air calibration may be necessary depending on the use case.

Also, an LSU 4.9 operates entirely differently to a 4.2. The calibration resistor is definitely not the only difference.

NTK UEGO sensors are the more common sensor to use if you wish to change the connectors, these do not have a calibration resistor in their connector so changing it isn't an issue.

The LSU ADV also has do away with the calibration resistor in the connector.

Haven't had one apart, but what's stopping you from measuring the resistor and adding one of the same value to the wiring for the new plug? Assuming there aren't other issue, of course.

LSU 4.9 sensors are a bit of a pain in as much as the wiring between the sensor body and connector make up part of the calibration the way the sensor is made. The wiring cannot be extended in any fashion and 50% of the time repairing the wiring will cause reading inaccuracies.

NTK UEGO also have an inbuilt factory trim resistor, particularly in the honda style 8 pin connector. This isn't 100% integral to the sensor operation, as the connector can be replaced with another connector - provided your lambda controller has the ability to fresh air calibrate the reading.

As black rex already covered the adv units are more finely calibrated and do not use a trim resistor in the connector.

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