How-to: Log a Wideband through the A/C Pressure Switch
Here is how to set-up your Wideband so that you can read it with your HPTuners Standard Cable (Pics will come later). It is not advisable to use your A/C while doing this, since your ECU won't be getting a reading of the actual A/C system's pressure.
A/C Pressure Sensor Wiring
• There are 3 wires connected to the A/C Pressure sensor. The Red wire with Black stripe is the one we want to use. I recommend that you buy a switch that will allow you to switch it one way it reads from the A/C sensor and switch it the other way to read from the Wideband O2 output wire. Or, if you don't ever use your A/C or have it removed, go ahead and hardwire it permanently.
HP Tuner Scanner
• Once you've finished up the wiring, you need to set up HPTuners to log it correctly. You will need some information on your specific wideband that will be in the widebands paperwork. You will have to set up a formula to change the voltage (0-5v or 0-4v... depending on which wideband you own) into your AFR wideband reading. It will look like this:
VOLTS / (VOLTAGE RANGE / DEVICE RANGE) + (MINIMUM VALUE OF DEVICE READING) = AFR
VOLTS = the voltage that the wideband 02 sensor is putting out to the EGR wire
VOLTAGE RANGE = typically 5v (0-5v), although some other companies like Autometer use a 4v (0-4v) range.
DEVICE RANGE = the range your wideband is set to read. If the wideband is set to read from 10 – 20 AFR, then the range will be 10. If set to read from 8 – 22 AFR, the range will be 14, etc.
MINIMUM VALUE OF DEVICE READING = the lowest number that your wideband is set to read. In the above examples, it would be 10 for the first example, and 8 for the second.
I am using an Autometer ES Wideband, so I will use it for my example. The formula will be:
VOLTS / (4/8) + 10 = AFR
or
(VOLTS / .5) + 10 = AFR
• Since HP Tuners Scanner will be using the A/C Pressure switch to get its readings from, we need to add that into the formula. The PID for the A/C Pressure Switch is PID.7101. Now the formula reads like this:
([PID.7101]/.5)+10 = AFR
Custom PID
• Open Table Display in Scanner
• Right click any blank line and choose Insert
• This will open the Insert PIDs display
• Here you will see PID List, AUX Input List and User Defined. Click the + next to User Defined to open the drop down list
• Double click Configure User Defined to open Configure User Defined Parameters
• Click on one of the numbers with <undefined> next to it
• For Name:, put the name of your choice, say, Air Fuel Ratio
• For Abbrv:, put AFR
• For Sensor:, open the drop down box and choose Air Fuel Ratio
• For Units:, open the drop down box and choose :1
• Under Function:, insert your formula: ([PID.7101]/.5)+10
• That’s it, just click the X at the top right to close the box and click the Save icon on the Histogram Configuration page.
• To make a custom PID for AFR % Error make your way back to the Configure User Defined Parameters page. There will already be an Air Fuel Ratio Error PID. Open it and look at the information in the Function box.
• Copy this formula EXACTLY. It will look like this:
100*([SENS.120]-[SENS.121])/[SENS.121]
• Since SENS.120 is the AFR SENSOR we want to create a new Custom PID and substitute our new formula in place of SENS.120, then enter this into the Function box. Now it will look like this:
100*((([PID.7101]/.5)+10)-[SENS.121])/[SENS.121]
• On this Custom PID, give it a name, use AFR%Error for the Abbrv, leave Sensor blank, and use % for Units.
• Now, you can change the information in your VE and MAF Error Histograms to use the custom PIDs that you just made so that you can log your AFR Error in order to more accurately tune your MAF and VE tables.
• Don’t forget that you will have to log A/C Pressure (PID List/System/AC/AC Pressure (V)), AFR, AFR % Error, and AFR Commanded in the Table display.
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I like my A/C Probably could do it with your fuel tank pressure sensor, especially if youre running the ZZP BRFPS or whatever its letters are 
Originally Posted by Maven
